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multi interfaces(vlans) configuration

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ahiya

multi interfaces(vlans) configuration

I'm new to isc/kea.I have multi-sites with around 2000-5000 devices per
site.the real issue is that they are spread across 500 different VLANs.I
wanted to know is isc/kea is the right solution for that task.and what is
the right way to implement it?if the only service I need is dhcp4 serving
all these segments, what will be the HW requirements for this task?
Raspberry PI4 with 8G mem will be enough?should I use .conf files or should
I go for the backend server?ill appreciate any feedback.thanks a lot.

--
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glenn.satchell

Re: multi interfaces(vlans) configuration

Hi,

The size of the server depends on two things - the number of clients and
how often they renew their lease.

Eg if they renew once every hour versus once every day then that takes
24 times as much cpu reources in the work done to renew the leases and
record the updates.

Secondly a large amount of the lease data is kept in memory, so the
number of lease affects the memory size.

So, how many sites? You say 500 vlans - which I guess equates to subnets
- that's what dhcpd configuration needs. And how many devices per subnet
typically? A subnet doesn't have to be a /24, it can be any size that is
suitable for that subnet, eg multiple /24 pools, /21 will give 2048
addresses, /20 will give 4096, or bigger if needed.

Others running large number of clients, say 10-20k can probably offer
better advice, but I don't think a PI4 with 8GB is not going to have
enough memory, cpu or storage I/O.

You'll probably want a server with 32 or 64GB memory and SSD or NVME
disks for high throughput. With that many clients then 10 or 25 Gigabit
network is probably needed too.

You'll also need to think about what bandwidth you have in your
back-haul networks back to the central network where the dhcp server is.

However, a PI4 is cheap so you could try one out to see how it goes.

regards,
-glenn

On 2020-10-08 15:57, ahiya wrote:

> I'm new to isc/kea.I have multi-sites with around 2000-5000 devices per
> site.the real issue is that they are spread across 500 different
> VLANs.I
> wanted to know is isc/kea is the right solution for that task.and what
> is
> the right way to implement it?if the only service I need is dhcp4
> serving
> all these segments, what will be the HW requirements for this task?
> Raspberry PI4 with 8G mem will be enough?should I use .conf files or
> should
> I go for the backend server?ill appreciate any feedback.thanks a lot.
>
>
>
> --
> Sent from: http://isc-dhcp-users.2343191.n4.nabble.com/
> _______________________________________________
> ISC funds the development of this software with paid support
> subscriptions. Contact us at https://www.isc.org/contact/ for more
> information.
>
> dhcp-users mailing list
> [hidden email]
> https://lists.isc.org/mailman/listinfo/dhcp-users

ahiya

RE: multi interfaces(vlans) configuration

Thanks, Glenn

Regarding the number of sites- I plan to have a server per site.
Each site will have around 500 subnets with around 10-15 devices per
subnet.
Does the number of IPs per subnet affect memory even when they are not
assigned?
This is MDUs installation so 24H lease is good enough.

-----Original Message-----
From: dhcp-users <[hidden email]> On Behalf Of
[hidden email]
Sent: Thursday, October 8, 2020 10:54 AM
To: Users of ISC DHCP <[hidden email]>
Subject: Re: multi interfaces(vlans) configuration

Hi,

The size of the server depends on two things - the number of clients and
how often they renew their lease.

Eg if they renew once every hour versus once every day then that takes
24 times as much cpu reources in the work done to renew the leases and
record the updates.

Secondly a large amount of the lease data is kept in memory, so the number
of lease affects the memory size.

So, how many sites? You say 500 vlans - which I guess equates to subnets
- that's what dhcpd configuration needs. And how many devices per subnet
typically? A subnet doesn't have to be a /24, it can be any size that is
suitable for that subnet, eg multiple /24 pools, /21 will give 2048
addresses, /20 will give 4096, or bigger if needed.

Others running large number of clients, say 10-20k can probably offer
better advice, but I don't think a PI4 with 8GB is not going to have
enough memory, cpu or storage I/O.

You'll probably want a server with 32 or 64GB memory and SSD or NVME disks
for high throughput. With that many clients then 10 or 25 Gigabit network
is probably needed too.

You'll also need to think about what bandwidth you have in your back-haul
networks back to the central network where the dhcp server is.

However, a PI4 is cheap so you could try one out to see how it goes.

regards,
-glenn

On 2020-10-08 15:57, ahiya wrote:

> I'm new to isc/kea.I have multi-sites with around 2000-5000 devices
> per site.the real issue is that they are spread across 500 different
> VLANs.I wanted to know is isc/kea is the right solution for that
> task.and what is the right way to implement it?if the only service I
> need is dhcp4 serving all these segments, what will be the HW
> requirements for this task?
> Raspberry PI4 with 8G mem will be enough?should I use .conf files or
> should I go for the backend server?ill appreciate any feedback.thanks
> a lot.
>
>
>
> --
> Sent from: http://isc-dhcp-users.2343191.n4.nabble.com/
> _______________________________________________
> ISC funds the development of this software with paid support
> subscriptions. Contact us at https://www.isc.org/contact/ for more
> information.
>
> dhcp-users mailing list
> [hidden email]
> https://lists.isc.org/mailman/listinfo/dhcp-users

glenn.satchell

Re: multi interfaces(vlans) configuration

Hi Ahiya

I'm not sure about memory usage per IP. I seem to vaguely remember that
having configuration with say a /16 subnet and only a few devices used a
lot more memory than a smaller subnet like a /24 with the same number of
devices.

With 24 hour lease a PI4 might get by. Based on a quick calculation of
my lease file, where I have just under 400 bytes per lease, I think
you'll need about 2MB for your leases file. This will need to be fast
storage such as an SSD.

As I said before a PI4 is cheap so you could buy one or two to try in
that size network. To keep your cost down I guess you could deploy more
than one PI4 at each site and split the subnet between them to create a
manageable workload if one PI4 wasn't powerful enough.

With that many subnets and sites I would look at a backend server that
used a database or spreadsheet to hold the data and a script to generate
all the configuration files and push them out to the individual servers
and restart the dhcpd service. That's going to make your life a lot
easier.

regards,
Glenn

On 2020-10-08 19:02, Ahiya Zadok wrote:

> Thanks, Glenn
>
> Regarding the number of sites- I plan to have a server per site.
> Each site will have around 500 subnets with around 10-15 devices per
> subnet.
> Does the number of IPs per subnet affect memory even when they are not
> assigned?
> This is MDUs installation so 24H lease is good enough.
>
>
> -----Original Message-----
> From: dhcp-users <[hidden email]> On Behalf Of
> [hidden email]
> Sent: Thursday, October 8, 2020 10:54 AM
> To: Users of ISC DHCP <[hidden email]>
> Subject: Re: multi interfaces(vlans) configuration
>
> Hi,
>
> The size of the server depends on two things - the number of clients
> and
> how often they renew their lease.
>
> Eg if they renew once every hour versus once every day then that takes
> 24 times as much cpu reources in the work done to renew the leases and
> record the updates.
>
> Secondly a large amount of the lease data is kept in memory, so the
> number
> of lease affects the memory size.
>
> So, how many sites? You say 500 vlans - which I guess equates to
> subnets
> - that's what dhcpd configuration needs. And how many devices per
> subnet
> typically? A subnet doesn't have to be a /24, it can be any size that
> is
> suitable for that subnet, eg multiple /24 pools, /21 will give 2048
> addresses, /20 will give 4096, or bigger if needed.
>
> Others running large number of clients, say 10-20k can probably offer
> better advice, but I don't think a PI4 with 8GB is not going to have
> enough memory, cpu or storage I/O.
>
> You'll probably want a server with 32 or 64GB memory and SSD or NVME
> disks
> for high throughput. With that many clients then 10 or 25 Gigabit
> network
> is probably needed too.
>
> You'll also need to think about what bandwidth you have in your
> back-haul
> networks back to the central network where the dhcp server is.
>
> However, a PI4 is cheap so you could try one out to see how it goes.
>
> regards,
> -glenn
>
> On 2020-10-08 15:57, ahiya wrote:
>> I'm new to isc/kea.I have multi-sites with around 2000-5000 devices
>> per site.the real issue is that they are spread across 500 different
>> VLANs.I wanted to know is isc/kea is the right solution for that
>> task.and what is the right way to implement it?if the only service I
>> need is dhcp4 serving all these segments, what will be the HW
>> requirements for this task?
>> Raspberry PI4 with 8G mem will be enough?should I use .conf files or
>> should I go for the backend server?ill appreciate any feedback.thanks
>> a lot.
>>
>>
>>
>> --
>> Sent from: http://isc-dhcp-users.2343191.n4.nabble.com/
>> _______________________________________________
>> ISC funds the development of this software with paid support
>> subscriptions. Contact us at https://www.isc.org/contact/ for more
>> information.
>>
>> dhcp-users mailing list
>> [hidden email]
>> https://lists.isc.org/mailman/listinfo/dhcp-users
> _______________________________________________
> ISC funds the development of this software with paid support
> subscriptions. Contact us at https://www.isc.org/contact/ for more
> information.
>
> dhcp-users mailing list
> [hidden email]
> https://lists.isc.org/mailman/listinfo/dhcp-users
> _______________________________________________
> ISC funds the development of this software with paid support
> subscriptions. Contact us at https://www.isc.org/contact/ for more
> information.
>
> dhcp-users mailing list
> [hidden email]
> https://lists.isc.org/mailman/listinfo/dhcp-users

Steve van der Burg

RE: multi interfaces(vlans) configuration

In reply to this post by ahiya

I'm serving leases from a total lease pool that has about a quarter of a million leasable addresses, with about 30k active leases at any one time. Most lease lengths are 60 hours (2.5 days) and those are all being served from a pair of single-CPU virtual machines (running Debian 10) with 2GB RAM each. And each one isn't really breaking a sweat. I rarely see more than 20% CPU usage and more than 75% of RAM used by dhcpd.

As Glenn said, lease length can make a big difference with regards to total traffic, CPU load, etc, but with lease lengths like mine you can see that you don't need much in the way of hardware.

...Steve

-----Original Message-----
From: dhcp-users <[hidden email]> On Behalf Of Ahiya Zadok
Sent: Thursday,October 08,2020 4:03 AM
To: Users of ISC DHCP <[hidden email]>
Subject: RE: multi interfaces(vlans) configuration

CAUTION: This email originated from outside the organization. Do not click links or open attachments unless you recognize the sender and know the content is safe.

Thanks, Glenn

Regarding the number of sites- I plan to have a server per site.
Each site will have around 500 subnets with around 10-15 devices per subnet.
Does the number of IPs per subnet affect memory even when they are not assigned?
This is MDUs installation so 24H lease is good enough.

-----Original Message-----
From: dhcp-users <[hidden email]> On Behalf Of [hidden email]
Sent: Thursday, October 8, 2020 10:54 AM
To: Users of ISC DHCP <[hidden email]>
Subject: Re: multi interfaces(vlans) configuration

Hi,

The size of the server depends on two things - the number of clients and how often they renew their lease.

Eg if they renew once every hour versus once every day then that takes
24 times as much cpu reources in the work done to renew the leases and record the updates.

Secondly a large amount of the lease data is kept in memory, so the number of lease affects the memory size.

So, how many sites? You say 500 vlans - which I guess equates to subnets
- that's what dhcpd configuration needs. And how many devices per subnet typically? A subnet doesn't have to be a /24, it can be any size that is suitable for that subnet, eg multiple /24 pools, /21 will give 2048 addresses, /20 will give 4096, or bigger if needed.

Others running large number of clients, say 10-20k can probably offer better advice, but I don't think a PI4 with 8GB is not going to have enough memory, cpu or storage I/O.

You'll probably want a server with 32 or 64GB memory and SSD or NVME disks for high throughput. With that many clients then 10 or 25 Gigabit network is probably needed too.

You'll also need to think about what bandwidth you have in your back-haul networks back to the central network where the dhcp server is.

However, a PI4 is cheap so you could try one out to see how it goes.

regards,
-glenn

On 2020-10-08 15:57, ahiya wrote:

ahiya

RE: multi interfaces(vlans) configuration

Thanks, Steve

Do you think that the numbers of subnets and the number of interfaces
(vlans) that DHCP is listening to have much effect on resource
utilization?

-----Original Message-----
From: dhcp-users <[hidden email]> On Behalf Of Steve van
der Burg
Sent: Thursday, October 8, 2020 3:01 PM
To: Users of ISC DHCP <[hidden email]>
Subject: RE: multi interfaces(vlans) configuration

I'm serving leases from a total lease pool that has about a quarter of a
million leasable addresses, with about 30k active leases at any one time.
Most lease lengths are 60 hours (2.5 days) and those are all being served
from a pair of single-CPU virtual machines (running Debian 10) with 2GB
RAM each. And each one isn't really breaking a sweat. I rarely see more
than 20% CPU usage and more than 75% of RAM used by dhcpd.

As Glenn said, lease length can make a big difference with regards to
total traffic, CPU load, etc, but with lease lengths like mine you can see
that you don't need much in the way of hardware.

...Steve

-----Original Message-----
From: dhcp-users <[hidden email]> On Behalf Of Ahiya
Zadok
Sent: Thursday,October 08,2020 4:03 AM
To: Users of ISC DHCP <[hidden email]>
Subject: RE: multi interfaces(vlans) configuration

CAUTION: This email originated from outside the organization. Do not click
links or open attachments unless you recognize the sender and know the
content is safe.

Thanks, Glenn

Regarding the number of sites- I plan to have a server per site.
Each site will have around 500 subnets with around 10-15 devices per
subnet.
Does the number of IPs per subnet affect memory even when they are not
assigned?
This is MDUs installation so 24H lease is good enough.

-----Original Message-----
From: dhcp-users <[hidden email]> On Behalf Of
[hidden email]
Sent: Thursday, October 8, 2020 10:54 AM
To: Users of ISC DHCP <[hidden email]>
Subject: Re: multi interfaces(vlans) configuration

Hi,

The size of the server depends on two things - the number of clients and
how often they renew their lease.

Eg if they renew once every hour versus once every day then that takes
24 times as much cpu reources in the work done to renew the leases and
record the updates.

Secondly a large amount of the lease data is kept in memory, so the number
of lease affects the memory size.

So, how many sites? You say 500 vlans - which I guess equates to subnets
- that's what dhcpd configuration needs. And how many devices per subnet
typically? A subnet doesn't have to be a /24, it can be any size that is
suitable for that subnet, eg multiple /24 pools, /21 will give 2048
addresses, /20 will give 4096, or bigger if needed.

Others running large number of clients, say 10-20k can probably offer
better advice, but I don't think a PI4 with 8GB is not going to have
enough memory, cpu or storage I/O.

You'll probably want a server with 32 or 64GB memory and SSD or NVME disks
for high throughput. With that many clients then 10 or 25 Gigabit network
is probably needed too.

You'll also need to think about what bandwidth you have in your back-haul
networks back to the central network where the dhcp server is.

However, a PI4 is cheap so you could try one out to see how it goes.

regards,
-glenn

On 2020-10-08 15:57, ahiya wrote:

Steve van der Burg

RE: multi interfaces(vlans) configuration

In my case (and in nearly all cases?) the DHCP traffic from the clients on those VLANs is being forwarded to the DHCP servers by the network gear. I don't run ours, but I know that our network people have added "DHCP helper address" settings to all (checking...) 2530 subnets. It all arrives on one interface on each of my DHCP servers. I can't imagine having 2500 virtual interfaces on either of those.

...Steve

-----Original Message-----
From: dhcp-users <[hidden email]> On Behalf Of Ahiya Zadok
Sent: Thursday,October 08,2020 8:08 AM
To: Users of ISC DHCP <[hidden email]>
Subject: RE: multi interfaces(vlans) configuration

CAUTION: This email originated from outside the organization. Do not click links or open attachments unless you recognize the sender and know the content is safe.

Thanks, Steve

Do you think that the numbers of subnets and the number of interfaces
(vlans) that DHCP is listening to have much effect on resource utilization?

-----Original Message-----
From: dhcp-users <[hidden email]> On Behalf Of Steve van der Burg
Sent: Thursday, October 8, 2020 3:01 PM
To: Users of ISC DHCP <[hidden email]>
Subject: RE: multi interfaces(vlans) configuration

I'm serving leases from a total lease pool that has about a quarter of a million leasable addresses, with about 30k active leases at any one time.
Most lease lengths are 60 hours (2.5 days) and those are all being served from a pair of single-CPU virtual machines (running Debian 10) with 2GB RAM each. And each one isn't really breaking a sweat. I rarely see more than 20% CPU usage and more than 75% of RAM used by dhcpd.

As Glenn said, lease length can make a big difference with regards to total traffic, CPU load, etc, but with lease lengths like mine you can see that you don't need much in the way of hardware.

...Steve

-----Original Message-----
From: dhcp-users <[hidden email]> On Behalf Of Ahiya Zadok
Sent: Thursday,October 08,2020 4:03 AM
To: Users of ISC DHCP <[hidden email]>
Subject: RE: multi interfaces(vlans) configuration

CAUTION: This email originated from outside the organization. Do not click links or open attachments unless you recognize the sender and know the content is safe.

Thanks, Glenn

Regarding the number of sites- I plan to have a server per site.
Each site will have around 500 subnets with around 10-15 devices per subnet.
Does the number of IPs per subnet affect memory even when they are not assigned?
This is MDUs installation so 24H lease is good enough.

-----Original Message-----
From: dhcp-users <[hidden email]> On Behalf Of [hidden email]
Sent: Thursday, October 8, 2020 10:54 AM
To: Users of ISC DHCP <[hidden email]>
Subject: Re: multi interfaces(vlans) configuration

Hi,

The size of the server depends on two things - the number of clients and how often they renew their lease.

Eg if they renew once every hour versus once every day then that takes
24 times as much cpu reources in the work done to renew the leases and record the updates.

Secondly a large amount of the lease data is kept in memory, so the number of lease affects the memory size.

So, how many sites? You say 500 vlans - which I guess equates to subnets
- that's what dhcpd configuration needs. And how many devices per subnet typically? A subnet doesn't have to be a /24, it can be any size that is suitable for that subnet, eg multiple /24 pools, /21 will give 2048 addresses, /20 will give 4096, or bigger if needed.

Others running large number of clients, say 10-20k can probably offer better advice, but I don't think a PI4 with 8GB is not going to have enough memory, cpu or storage I/O.

You'll probably want a server with 32 or 64GB memory and SSD or NVME disks for high throughput. With that many clients then 10 or 25 Gigabit network is probably needed too.

You'll also need to think about what bandwidth you have in your back-haul networks back to the central network where the dhcp server is.

However, a PI4 is cheap so you could try one out to see how it goes.

regards,
-glenn

On 2020-10-08 15:57, ahiya wrote:

_______________________________________________
ISC funds the development of this software with paid support subscriptions. Contact us at https://www.isc.org/contact/ for more information.

dhcp-users mailing list
[hidden email]
https://lists.isc.org/mailman/listinfo/dhcp-users
_______________________________________________
ISC funds the development of this software with paid support subscriptions. Contact us at https://www.isc.org/contact/ for more information.

dhcp-users mailing list
[hidden email]
https://lists.isc.org/mailman/listinfo/dhcp-users

This email is directed in confidence solely to the person named above and may contain confidential, privileged or personal health information.
Please be aware that this email may also be released to members of the public under Ontario's Freedom of Information and Protection of Privacy Act if required. Review, distribution, or disclosure of this email by anyone other than the person(s) for whom it was originally intended is strictly prohibited. If you are not an intended recipient, please notify the sender immediately via a return email and destroy all copies of the original message. Thank you for your cooperation.
_______________________________________________
ISC funds the development of this software with paid support subscriptions. Contact us at https://www.isc.org/contact/ for more information.

dhcp-users mailing list
[hidden email]
https://lists.isc.org/mailman/listinfo/dhcp-users
_______________________________________________
ISC funds the development of this software with paid support subscriptions. Contact us at https://www.isc.org/contact/ for more information.

dhcp-users mailing list
[hidden email]
https://lists.isc.org/mailman/listinfo/dhcp-users

This email is directed in confidence solely to the person named above and may contain confidential, privileged or personal health information. Please be aware that this email may also be released to members of the public under Ontario's Freedom of Information and Protection of Privacy Act if required. Review, distribution, or disclosure of this email by anyone other than the person(s) for whom it was originally intended is strictly prohibited. If you are not an intended recipient, please notify the sender immediately via a return email and destroy all copies of the original message. Thank you for your cooperation.
_______________________________________________
ISC funds the development of this software with paid support subscriptions. Contact us at https://www.isc.org/contact/ for more information.

dhcp-users mailing list
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ahiya

RE: multi interfaces(vlans) configuration

Thanks

The network gear in my sites is the bottleneck
It supports up to 256 DHCP servers/relay agents.
Do you think that raspberry pi could handle 500 VLAN interfaces?

-----Original Message-----
From: dhcp-users <[hidden email]> On Behalf Of Steve van
der Burg
Sent: Thursday, October 8, 2020 3:20 PM
To: Users of ISC DHCP <[hidden email]>
Subject: RE: multi interfaces(vlans) configuration

In my case (and in nearly all cases?) the DHCP traffic from the clients on
those VLANs is being forwarded to the DHCP servers by the network gear. I
don't run ours, but I know that our network people have added "DHCP helper
address" settings to all (checking...) 2530 subnets. It all arrives on
one interface on each of my DHCP servers. I can't imagine having 2500
virtual interfaces on either of those.

...Steve

-----Original Message-----
From: dhcp-users <[hidden email]> On Behalf Of Ahiya
Zadok
Sent: Thursday,October 08,2020 8:08 AM
To: Users of ISC DHCP <[hidden email]>
Subject: RE: multi interfaces(vlans) configuration

CAUTION: This email originated from outside the organization. Do not click
links or open attachments unless you recognize the sender and know the
content is safe.

Thanks, Steve

Do you think that the numbers of subnets and the number of interfaces
(vlans) that DHCP is listening to have much effect on resource
utilization?

-----Original Message-----
From: dhcp-users <[hidden email]> On Behalf Of Steve van
der Burg
Sent: Thursday, October 8, 2020 3:01 PM
To: Users of ISC DHCP <[hidden email]>
Subject: RE: multi interfaces(vlans) configuration

I'm serving leases from a total lease pool that has about a quarter of a
million leasable addresses, with about 30k active leases at any one time.
Most lease lengths are 60 hours (2.5 days) and those are all being served
from a pair of single-CPU virtual machines (running Debian 10) with 2GB
RAM each. And each one isn't really breaking a sweat. I rarely see more
than 20% CPU usage and more than 75% of RAM used by dhcpd.

As Glenn said, lease length can make a big difference with regards to
total traffic, CPU load, etc, but with lease lengths like mine you can see
that you don't need much in the way of hardware.

...Steve

-----Original Message-----
From: dhcp-users <[hidden email]> On Behalf Of Ahiya
Zadok
Sent: Thursday,October 08,2020 4:03 AM
To: Users of ISC DHCP <[hidden email]>
Subject: RE: multi interfaces(vlans) configuration

CAUTION: This email originated from outside the organization. Do not click
links or open attachments unless you recognize the sender and know the
content is safe.

Thanks, Glenn

Regarding the number of sites- I plan to have a server per site.
Each site will have around 500 subnets with around 10-15 devices per
subnet.
Does the number of IPs per subnet affect memory even when they are not
assigned?
This is MDUs installation so 24H lease is good enough.

-----Original Message-----
From: dhcp-users <[hidden email]> On Behalf Of
[hidden email]
Sent: Thursday, October 8, 2020 10:54 AM
To: Users of ISC DHCP <[hidden email]>
Subject: Re: multi interfaces(vlans) configuration

Hi,

The size of the server depends on two things - the number of clients and
how often they renew their lease.

Eg if they renew once every hour versus once every day then that takes
24 times as much cpu reources in the work done to renew the leases and
record the updates.

Secondly a large amount of the lease data is kept in memory, so the number
of lease affects the memory size.

So, how many sites? You say 500 vlans - which I guess equates to subnets
- that's what dhcpd configuration needs. And how many devices per subnet
typically? A subnet doesn't have to be a /24, it can be any size that is
suitable for that subnet, eg multiple /24 pools, /21 will give 2048
addresses, /20 will give 4096, or bigger if needed.

Others running large number of clients, say 10-20k can probably offer
better advice, but I don't think a PI4 with 8GB is not going to have
enough memory, cpu or storage I/O.

You'll probably want a server with 32 or 64GB memory and SSD or NVME disks
for high throughput. With that many clients then 10 or 25 Gigabit network
is probably needed too.

You'll also need to think about what bandwidth you have in your back-haul
networks back to the central network where the dhcp server is.

However, a PI4 is cheap so you could try one out to see how it goes.

regards,
-glenn

On 2020-10-08 15:57, ahiya wrote:

_______________________________________________
ISC funds the development of this software with paid support
subscriptions. Contact us at https://www.isc.org/contact/ for more
information.

dhcp-users mailing list
[hidden email]
https://lists.isc.org/mailman/listinfo/dhcp-users
_______________________________________________
ISC funds the development of this software with paid support
subscriptions. Contact us at https://www.isc.org/contact/ for more
information.

dhcp-users mailing list
[hidden email]
https://lists.isc.org/mailman/listinfo/dhcp-users

This email is directed in confidence solely to the person named above and
may contain confidential, privileged or personal health information.
Please be aware that this email may also be released to members of the
public under Ontario's Freedom of Information and Protection of Privacy
Act if required. Review, distribution, or disclosure of this email by
anyone other than the person(s) for whom it was originally intended is
strictly prohibited. If you are not an intended recipient, please notify
the sender immediately via a return email and destroy all copies of the
original message. Thank you for your cooperation.
_______________________________________________
ISC funds the development of this software with paid support
subscriptions. Contact us at https://www.isc.org/contact/ for more
information.

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Simon Hobson

Re: multi interfaces(vlans) configuration

In reply to this post by ahiya

ahiya <[hidden email]> wrote:

> I'm new to isc/kea.I have multi-sites with around 2000-5000 devices per
> site.the real issue is that they are spread across 500 different VLANs.I
> wanted to know is isc/kea is the right solution for that task.and what is
> the right way to implement it?

There isn't really a right or wrong way to do it - just different trade-offs.

> Raspberry PI4 with 8G mem will be enough?

I've not kept up, but does the Pi4 now have a proper ethernet and means of attaching a disk ? I know earlier models had a USB-ethernet bridge which is far from ideal.

> should I use .conf files or should I go for the backend server?

As another has said, you would be well advised to automate with that size of setup. Manually configuring that size of config (without errors !) will be a nightmare - so put the config in some sort of config management and script generation of the config files for the servers.

Ahiya Zadok <[hidden email]> wrote:

> Regarding the number of sites- I plan to have a server per site.
> Each site will have around 500 subnets with around 10-15 devices per
> subnet.
> Does the number of IPs per subnet affect memory even when they are not
> assigned?

Yes, memory requirements scale (I believe) roughly linearly with number of IP addresses available in your config - even those that have never been assigned. So the size of each pool in each of your 500 subnets will make a massive difference to memory requirements.
Note that once an IP has every been leased to a client, it will remain in the leases file "forever". The server will never delete it unless you remove the IP address from the config (remove/change a range). Eventually, when all addresses have been used once, the server will start to re-used old leases in a least recently used manner.

Ahiya Zadok <[hidden email]> wrote:

> Do you think that the numbers of subnets and the number of interfaces
> (vlans) that DHCP is listening to have much effect on resource
> utilization?

No, number of subnets makes a fairly small impact on memory requirements - it's number of IP address that makes the big difference. So 500 subnets with (say) 50 IPs each (250,000 in all) will take a lot less memory than the same 500 subnets with (say) 250 IPs each (1,250,000 in all).

Ahiya Zadok <[hidden email]> wrote:

> The network gear in my sites is the bottleneck
> It supports up to 256 DHCP servers/relay agents.

Are you sure that's a limitation ? In principle you only need one or two (if you use failover) per network device - remember you only have one or two servers to forward requests to. I would be surprised if a device didn't support at least one ip-helper per interface, or a small number globally.

> Do you think that raspberry pi could handle 500 VLAN interfaces?

I've never gone about 30-something interfaces in Linux. In principle I would have thought it could handle it - we hear of people running hundreds of virtual machines on a host, and each of those gets one (or more) virtual network interfaces. But it's probably easier to just add one (or two) ip-helper addresses to the routers.

A few more thoughts in no particular order ...

What are you planning to do regarding fault tolerance ? With that many devices, I imagine loss of the DHCP service would quickly start to cause problems - and the corresponding enquiries from customers. You could run two servers per site - either in failover, or with non-overlapping ranges but the same subnets. The latter would mean clients changing address is the server they got their address from fails, and the DNS would not get updated - but they would continue to work.

One idea from a long time ago was to run small servers out in the network, and a central massive server. Each small server would have a failover relationship with the central server - so the central server would hold a copy of all the leases (where it's relatively easy to provide fault tolerance (RAID, UPS, etc) and backup.
At the edge, the servers would run diskless, storing the lease database on ramdisk - and after a restart would load the leases database from the central server via failover. Whether this would work with that many clients per site would be interesting to know.
You don't have to run diskless at the edge - that was mainly a suggestion to avoid all the issues that come with having storage dotted around remote sites where it's hard to manage and involves an engineer visit if anything goes wrong.
During normal operations, clients will use the local server because it will normally respond first due to being closer (in terms of network links and latency). If the local server is down, they will be able to use the central server.

When sizing the system, you need to consider other than just the steady state. Even a modest server can manage many clients if the leases are long - but what happens if there's a mass event such as a power cut that causes many clients to re-connect in a short space of time ?
In such an event, your server will experience a significantly higher load - which will be higher if all the devices auto-startup when power is restored, but lower if it's (e.g.) desktop systems that need the user to power them on. It's not as simple as "a queue will form".
If the server can't cope, clients will send a request, and eventually time out waiting for a reply - they'll then send another request, and another, and ... with man of the requests getting dropped. That in itself might not be too bad - clients would be happy when they hit the jackpot and their packet in one of the ones that didn't get dropped. But it's not that simple - many devices (and every device without both a real time clock and persistent storage) will first send a discover, then after it gets an offer will send a request (the DORA cycle, Discover-Offer-request-Ack). If the client doesn't get an Ack to it's request, it will eventually go back to sending Discovers.
In extreme, it could be a very long time before clients get addresses and the load dies down. And disk usage (for the leases file) will also temporarily increase - each transaction results in a new record being appended to the end of the file.

Simon

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glenn.satchell

Re: multi interfaces(vlans) configuration

In reply to this post by ahiya

If you have a router forwarding packets between subnets, then the dhcp
server only has to be connected to a single vlan - the router can
forward dhcp broadcasts to the server. So you don't need 500 interfaces
on your dhcp server.

regards,
-glenn

On 2020-10-08 23:07, Ahiya Zadok wrote:

> Thanks, Steve
>
> Do you think that the numbers of subnets and the number of interfaces
> (vlans) that DHCP is listening to have much effect on resource
> utilization?
>
>
> -----Original Message-----
> From: dhcp-users <[hidden email]> On Behalf Of Steve
> van
> der Burg
> Sent: Thursday, October 8, 2020 3:01 PM
> To: Users of ISC DHCP <[hidden email]>
> Subject: RE: multi interfaces(vlans) configuration
>
> I'm serving leases from a total lease pool that has about a quarter of
> a
> million leasable addresses, with about 30k active leases at any one
> time.
> Most lease lengths are 60 hours (2.5 days) and those are all being
> served
> from a pair of single-CPU virtual machines (running Debian 10) with 2GB
> RAM each. And each one isn't really breaking a sweat. I rarely see
> more
> than 20% CPU usage and more than 75% of RAM used by dhcpd.
>
> As Glenn said, lease length can make a big difference with regards to
> total traffic, CPU load, etc, but with lease lengths like mine you can
> see
> that you don't need much in the way of hardware.
>
> ...Steve
>
> -----Original Message-----
> From: dhcp-users <[hidden email]> On Behalf Of Ahiya
> Zadok
> Sent: Thursday,October 08,2020 4:03 AM
> To: Users of ISC DHCP <[hidden email]>
> Subject: RE: multi interfaces(vlans) configuration
>
> CAUTION: This email originated from outside the organization. Do not
> click
> links or open attachments unless you recognize the sender and know the
> content is safe.
>
> Thanks, Glenn
>
> Regarding the number of sites- I plan to have a server per site.
> Each site will have around 500 subnets with around 10-15 devices per
> subnet.
> Does the number of IPs per subnet affect memory even when they are not
> assigned?
> This is MDUs installation so 24H lease is good enough.
>
>
> -----Original Message-----
> From: dhcp-users <[hidden email]> On Behalf Of
> [hidden email]
> Sent: Thursday, October 8, 2020 10:54 AM
> To: Users of ISC DHCP <[hidden email]>
> Subject: Re: multi interfaces(vlans) configuration
>
> Hi,
>
> The size of the server depends on two things - the number of clients
> and
> how often they renew their lease.
>
> Eg if they renew once every hour versus once every day then that takes
> 24 times as much cpu reources in the work done to renew the leases and
> record the updates.
>
> Secondly a large amount of the lease data is kept in memory, so the
> number
> of lease affects the memory size.
>
> So, how many sites? You say 500 vlans - which I guess equates to
> subnets
> - that's what dhcpd configuration needs. And how many devices per
> subnet
> typically? A subnet doesn't have to be a /24, it can be any size that
> is
> suitable for that subnet, eg multiple /24 pools, /21 will give 2048
> addresses, /20 will give 4096, or bigger if needed.
>
> Others running large number of clients, say 10-20k can probably offer
> better advice, but I don't think a PI4 with 8GB is not going to have
> enough memory, cpu or storage I/O.
>
> You'll probably want a server with 32 or 64GB memory and SSD or NVME
> disks
> for high throughput. With that many clients then 10 or 25 Gigabit
> network
> is probably needed too.
>
> You'll also need to think about what bandwidth you have in your
> back-haul
> networks back to the central network where the dhcp server is.
>
> However, a PI4 is cheap so you could try one out to see how it goes.
>
> regards,
> -glenn
>
> On 2020-10-08 15:57, ahiya wrote:
>> I'm new to isc/kea.I have multi-sites with around 2000-5000 devices
>> per site.the real issue is that they are spread across 500 different
>> VLANs.I wanted to know is isc/kea is the right solution for that
>> task.and what is the right way to implement it?if the only service I
>> need is dhcp4 serving all these segments, what will be the HW
>> requirements for this task?
>> Raspberry PI4 with 8G mem will be enough?should I use .conf files or
>> should I go for the backend server?ill appreciate any feedback.thanks
>> a lot.
>>
>>
>>
>> --
>> Sent from: http://isc-dhcp-users.2343191.n4.nabble.com/
>> _______________________________________________
>> ISC funds the development of this software with paid support
>> subscriptions. Contact us at https://www.isc.org/contact/ for more
>> information.
>>
>> dhcp-users mailing list
>> [hidden email]
>> https://lists.isc.org/mailman/listinfo/dhcp-users
> _______________________________________________
> ISC funds the development of this software with paid support
> subscriptions. Contact us at https://www.isc.org/contact/ for more
> information.
>
> dhcp-users mailing list
> [hidden email]
> https://lists.isc.org/mailman/listinfo/dhcp-users
> _______________________________________________
> ISC funds the development of this software with paid support
> subscriptions. Contact us at https://www.isc.org/contact/ for more
> information.
>
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> https://lists.isc.org/mailman/listinfo/dhcp-users
>
> This email is directed in confidence solely to the person named above
> and
> may contain confidential, privileged or personal health information.
> Please be aware that this email may also be released to members of the
> public under Ontario's Freedom of Information and Protection of Privacy
> Act if required. Review, distribution, or disclosure of this email by
> anyone other than the person(s) for whom it was originally intended is
> strictly prohibited. If you are not an intended recipient, please
> notify
> the sender immediately via a return email and destroy all copies of the
> original message. Thank you for your cooperation.
> _______________________________________________
> ISC funds the development of this software with paid support
> subscriptions. Contact us at https://www.isc.org/contact/ for more
> information.
>
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glenn.satchell

Re: multi interfaces(vlans) configuration

In reply to this post by ahiya

ISC dhcpd needs to access the raw ethernet interface, so doesn't play
well with vlan sub-interfaces.

You don't have 256 different dhcp servers, only one. Typically in the
router each interface definition will include a dhcp relay or
ip-forwarder, and this will always be the same the single IP address of
your dhcp server.

If that doesn't work you may be able to set the dhcp relay in your
switches as an alternative.

regards,
Glenn

On 2020-10-09 01:25, Ahiya Zadok wrote:

> Thanks
>
> The network gear in my sites is the bottleneck
> It supports up to 256 DHCP servers/relay agents.
> Do you think that raspberry pi could handle 500 VLAN interfaces?
>
>
> -----Original Message-----
> From: dhcp-users <[hidden email]> On Behalf Of Steve
> van
> der Burg
> Sent: Thursday, October 8, 2020 3:20 PM
> To: Users of ISC DHCP <[hidden email]>
> Subject: RE: multi interfaces(vlans) configuration
>
> In my case (and in nearly all cases?) the DHCP traffic from the clients
> on
> those VLANs is being forwarded to the DHCP servers by the network gear.
> I
> don't run ours, but I know that our network people have added "DHCP
> helper
> address" settings to all (checking...) 2530 subnets. It all arrives on
> one interface on each of my DHCP servers. I can't imagine having 2500
> virtual interfaces on either of those.
>
> ...Steve
>
> -----Original Message-----
> From: dhcp-users <[hidden email]> On Behalf Of Ahiya
> Zadok
> Sent: Thursday,October 08,2020 8:08 AM
> To: Users of ISC DHCP <[hidden email]>
> Subject: RE: multi interfaces(vlans) configuration
>
> CAUTION: This email originated from outside the organization. Do not
> click
> links or open attachments unless you recognize the sender and know the
> content is safe.
>
> Thanks, Steve
>
> Do you think that the numbers of subnets and the number of interfaces
> (vlans) that DHCP is listening to have much effect on resource
> utilization?
>
>
> -----Original Message-----
> From: dhcp-users <[hidden email]> On Behalf Of Steve
> van
> der Burg
> Sent: Thursday, October 8, 2020 3:01 PM
> To: Users of ISC DHCP <[hidden email]>
> Subject: RE: multi interfaces(vlans) configuration
>
> I'm serving leases from a total lease pool that has about a quarter of
> a
> million leasable addresses, with about 30k active leases at any one
> time.
> Most lease lengths are 60 hours (2.5 days) and those are all being
> served
> from a pair of single-CPU virtual machines (running Debian 10) with 2GB
> RAM each. And each one isn't really breaking a sweat. I rarely see
> more
> than 20% CPU usage and more than 75% of RAM used by dhcpd.
>
> As Glenn said, lease length can make a big difference with regards to
> total traffic, CPU load, etc, but with lease lengths like mine you can
> see
> that you don't need much in the way of hardware.
>
> ...Steve
>
> -----Original Message-----
> From: dhcp-users <[hidden email]> On Behalf Of Ahiya
> Zadok
> Sent: Thursday,October 08,2020 4:03 AM
> To: Users of ISC DHCP <[hidden email]>
> Subject: RE: multi interfaces(vlans) configuration
>
> CAUTION: This email originated from outside the organization. Do not
> click
> links or open attachments unless you recognize the sender and know the
> content is safe.
>
> Thanks, Glenn
>
> Regarding the number of sites- I plan to have a server per site.
> Each site will have around 500 subnets with around 10-15 devices per
> subnet.
> Does the number of IPs per subnet affect memory even when they are not
> assigned?
> This is MDUs installation so 24H lease is good enough.
>
>
> -----Original Message-----
> From: dhcp-users <[hidden email]> On Behalf Of
> [hidden email]
> Sent: Thursday, October 8, 2020 10:54 AM
> To: Users of ISC DHCP <[hidden email]>
> Subject: Re: multi interfaces(vlans) configuration
>
> Hi,
>
> The size of the server depends on two things - the number of clients
> and
> how often they renew their lease.
>
> Eg if they renew once every hour versus once every day then that takes
> 24 times as much cpu reources in the work done to renew the leases and
> record the updates.
>
> Secondly a large amount of the lease data is kept in memory, so the
> number
> of lease affects the memory size.
>
> So, how many sites? You say 500 vlans - which I guess equates to
> subnets
> - that's what dhcpd configuration needs. And how many devices per
> subnet
> typically? A subnet doesn't have to be a /24, it can be any size that
> is
> suitable for that subnet, eg multiple /24 pools, /21 will give 2048
> addresses, /20 will give 4096, or bigger if needed.
>
> Others running large number of clients, say 10-20k can probably offer
> better advice, but I don't think a PI4 with 8GB is not going to have
> enough memory, cpu or storage I/O.
>
> You'll probably want a server with 32 or 64GB memory and SSD or NVME
> disks
> for high throughput. With that many clients then 10 or 25 Gigabit
> network
> is probably needed too.
>
> You'll also need to think about what bandwidth you have in your
> back-haul
> networks back to the central network where the dhcp server is.
>
> However, a PI4 is cheap so you could try one out to see how it goes.
>
> regards,
> -glenn
>
> On 2020-10-08 15:57, ahiya wrote:
>> I'm new to isc/kea.I have multi-sites with around 2000-5000 devices
>> per site.the real issue is that they are spread across 500 different
>> VLANs.I wanted to know is isc/kea is the right solution for that
>> task.and what is the right way to implement it?if the only service I
>> need is dhcp4 serving all these segments, what will be the HW
>> requirements for this task?
>> Raspberry PI4 with 8G mem will be enough?should I use .conf files or
>> should I go for the backend server?ill appreciate any feedback.thanks
>> a lot.
>>
>>
>>
>> --
>> Sent from: http://isc-dhcp-users.2343191.n4.nabble.com/
>> _______________________________________________
>> ISC funds the development of this software with paid support
>> subscriptions. Contact us at https://www.isc.org/contact/ for more
>> information.
>>
>> dhcp-users mailing list
>> [hidden email]
>> https://lists.isc.org/mailman/listinfo/dhcp-users
> _______________________________________________
> ISC funds the development of this software with paid support
> subscriptions. Contact us at https://www.isc.org/contact/ for more
> information.
>
> dhcp-users mailing list
> [hidden email]
> https://lists.isc.org/mailman/listinfo/dhcp-users
> _______________________________________________
> ISC funds the development of this software with paid support
> subscriptions. Contact us at https://www.isc.org/contact/ for more
> information.
>
> dhcp-users mailing list
> [hidden email]
> https://lists.isc.org/mailman/listinfo/dhcp-users
>
> This email is directed in confidence solely to the person named above
> and
> may contain confidential, privileged or personal health information.
> Please be aware that this email may also be released to members of the
> public under Ontario's Freedom of Information and Protection of Privacy
> Act if required. Review, distribution, or disclosure of this email by
> anyone other than the person(s) for whom it was originally intended is
> strictly prohibited. If you are not an intended recipient, please
> notify
> the sender immediately via a return email and destroy all copies of the
> original message. Thank you for your cooperation.
> _______________________________________________
> ISC funds the development of this software with paid support
> subscriptions. Contact us at https://www.isc.org/contact/ for more
> information.
>
> dhcp-users mailing list
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> https://lists.isc.org/mailman/listinfo/dhcp-users
> _______________________________________________
> ISC funds the development of this software with paid support
> subscriptions. Contact us at https://www.isc.org/contact/ for more
> information.
>
> dhcp-users mailing list
> [hidden email]
> https://lists.isc.org/mailman/listinfo/dhcp-users
>
> This email is directed in confidence solely to the person named above
> and
> may contain confidential, privileged or personal health information.
> Please be aware that this email may also be released to members of the
> public under Ontario's Freedom of Information and Protection of Privacy
> Act if required. Review, distribution, or disclosure of this email by
> anyone other than the person(s) for whom it was originally intended is
> strictly prohibited. If you are not an intended recipient, please
> notify
> the sender immediately via a return email and destroy all copies of the
> original message. Thank you for your cooperation.
> _______________________________________________
> ISC funds the development of this software with paid support
> subscriptions. Contact us at https://www.isc.org/contact/ for more
> information.
>
> dhcp-users mailing list
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> information.
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sthaug

Re: multi interfaces(vlans) configuration

> ISC dhcpd needs to access the raw ethernet interface, so doesn't play
> well with vlan sub-interfaces.

"Doesn't play well with vlan sub-interfaces" may be the case for Linux.
We're running ISC dcpd with multiple VLANs on FreeBSD, and it seems to
work just fine.

Steinar Haug, Nethelp consulting, [hidden email]
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Simon Hobson

Re: multi interfaces(vlans) configuration

> On 9 Oct 2020, at 07:02, [hidden email] wrote:
>
>> ISC dhcpd needs to access the raw ethernet interface, so doesn't play
>> well with vlan sub-interfaces.
>
> "Doesn't play well with vlan sub-interfaces" may be the case for Linux.
> We're running ISC dcpd with multiple VLANs on FreeBSD, and it seems to
> work just fine.

I'm pretty certain I've done it with linux in the past. Does "raw packet" literally mean "packet from the NIC buffer", or does it mean "packet from the OS buffer after the OS has done the VLAN stuff" ?
Without any knowledge of how it's actually done, it would seem logical to me for the VLAN (and link aggregation/bonding) code to handle that aspect before squirting the packet into the packet buffer ready to go into the rest of the network stack. So tagged packet in -> tag stripped by VLAN code -> packet put into buffer as though it had been received that way (untagged) on that interface.

Simon
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ahiya

RE: multi interfaces(vlans) configuration

Eventually, I understood that the DHCP relay limitation isn't real
I was misled by the vendor's support engineer.

Thank you all for responding

-----Original Message-----
From: dhcp-users <[hidden email]> On Behalf Of Simon
Hobson
Sent: Friday, October 9, 2020 5:17 PM
To: Users of ISC DHCP <[hidden email]>
Subject: Re: multi interfaces(vlans) configuration

> On 9 Oct 2020, at 07:02, [hidden email] wrote:
>
>> ISC dhcpd needs to access the raw ethernet interface, so doesn't play
>> well with vlan sub-interfaces.
>
> "Doesn't play well with vlan sub-interfaces" may be the case for Linux.
> We're running ISC dcpd with multiple VLANs on FreeBSD, and it seems to
> work just fine.

I'm pretty certain I've done it with linux in the past. Does "raw packet"
literally mean "packet from the NIC buffer", or does it mean "packet from
the OS buffer after the OS has done the VLAN stuff" ?
Without any knowledge of how it's actually done, it would seem logical to
me for the VLAN (and link aggregation/bonding) code to handle that aspect
before squirting the packet into the packet buffer ready to go into the
rest of the network stack. So tagged packet in -> tag stripped by VLAN
code -> packet put into buffer as though it had been received that way
(untagged) on that interface.

Simon
_______________________________________________
ISC funds the development of this software with paid support
subscriptions. Contact us at https://www.isc.org/contact/ for more
information.

dhcp-users mailing list
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Simon Hobson

Re: multi interfaces(vlans) configuration

Ahiya Zadok <[hidden email]> wrote:

> Eventually, I understood that the DHCP relay limitation isn't real
> I was misled by the vendor's support engineer.

I think we've all been there :-(

Simon
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