VLAN and fixed IPs

[Jan Lundmark]

 

 

 

Hi,

 

We have an application where we want the clients to  have fixed IPs and that the clients are all on the same subnet.

It is not practical for our application to use the MAC adresses of the clients.

 

This configuration below will assign a somewhat fixed IP based on the VLAN  subnets but it is not exactly what we want.

The point is that we want each client to receive a fixed IP address based on their port in the switch.

 

/etc/network/interfaces:

# VLAN 2

iface eth0.2 inet static

address 192.168.5.1

netmask 255.255.255.0

vlan_raw_device eth0

 

# VLAN 3

iface eth0.3 inet static

address 192.168.6.1

netmask 255.255.255.0

vlan_raw_device eth0

 

/etc/dhcp/dhcpd.conf

# VLAN 2DHCP

subnet 192.168.5.0 netmask 255.255.255.0 {

                range 192.168.5.50 192.168.5.200;

}

 

# VLAN 3

subnet 192.168.6.0 netmask 255.255.255.0 {

                range 192.168.6.50 192.168.6.200;

}

 

 

So, my question is:

 

Is there a way to assign fixed IP(v4) adresses in dhcpd.conf to clients based on their VLAN membership instead of their subnet?

 

Regards

 

Jan

 

 

 

 

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[José Queiroz]

Why don't you give your devices a loooong lease, so the addresses get fixed to the devices, once assigned?

2017-09-28 6:33 GMT-03:00 Jan Lundmark <[hidden email]>:

 

 

 

Hi,

 

We have an application where we want the clients to  have fixed IPs and that the clients are all on the same subnet.

It is not practical for our application to use the MAC adresses of the clients.

 

This configuration below will assign a somewhat fixed IP based on the VLAN  subnets but it is not exactly what we want.

The point is that we want each client to receive a fixed IP address based on their port in the switch.

 

/etc/network/interfaces:

# VLAN 2

iface eth0.2 inet static

address 192.168.5.1

netmask 255.255.255.0

vlan_raw_device eth0

 

# VLAN 3

iface eth0.3 inet static

address 192.168.6.1

netmask 255.255.255.0

vlan_raw_device eth0

 

/etc/dhcp/dhcpd.conf

# VLAN 2DHCP

subnet 192.168.5.0 netmask 255.255.255.0 {

                range 192.168.5.50 192.168.5.200;

}

 

# VLAN 3

subnet 192.168.6.0 netmask 255.255.255.0 {

                range 192.168.6.50 192.168.6.200;

}

 

 

So, my question is:

 

Is there a way to assign fixed IP(v4) adresses in dhcpd.conf to clients based on their VLAN membership instead of their subnet?

 

Regards

 

Jan

 

 

 

 

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[Christian Kratzer]

Hi,

On Thu, 28 Sep 2017, Jan Lundmark wrote:

>
>
>
> Hi,
>
> We have an application where we want the clients to  have fixed IPs and that the clients are all on the same subnet.
> It is not practical for our application to use the MAC adresses of the clients.
>
> This configuration below will assign a somewhat fixed IP based on the VLAN  subnets but it is not exactly what we want.
> The point is that we want each client to receive a fixed IP address based on their port in the switch.

<snipp/>

dhcp snooping on some switches is able to insert realay agent options into packets passing by even in pure l2 environments.

You can then assign fixed ip based on option82 circuit-id or remote-id options.

Greetings
Christian

--
Christian Kratzer                   CK Software GmbH
Email:   [hidden email]               Wildberger Weg 24/2
Phone:   [phone] - 0       D-71126 Gaeufelden
Fax:     [phone] - 9       HRB 245288, Amtsgericht Stuttgart
Mobile:  [phone]           Geschaeftsfuehrer: Christian Kratzer
Web:     http://www.cksoft.de/
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[Patrick Trapp]

Seconding Christian's suggestion if your relay agent will support it.

-----Original Message-----
From: dhcp-users [mailto:[hidden email]] On Behalf Of Christian Kratzer
Sent: Thursday, September 28, 2017 4:48 AM
To: Users of ISC DHCP <[hidden email]>
Subject: Re: VLAN and fixed IPs

Hi,

On Thu, 28 Sep 2017, Jan Lundmark wrote:

>
>
>
> Hi,
>
> We have an application where we want the clients to  have fixed IPs and that the clients are all on the same subnet.
> It is not practical for our application to use the MAC adresses of the clients.
>
> This configuration below will assign a somewhat fixed IP based on the VLAN  subnets but it is not exactly what we want.
> The point is that we want each client to receive a fixed IP address based on their port in the switch.

<snipp/>

dhcp snooping on some switches is able to insert realay agent options into packets passing by even in pure l2 environments.

You can then assign fixed ip based on option82 circuit-id or remote-id options.

Greetings
Christian

--
Christian Kratzer                   CK Software GmbH
Email:   [hidden email]               Wildberger Weg 24/2
Phone:   [phone] - 0       D-71126 Gaeufelden
Fax:     [phone] - 9       HRB 245288, Amtsgericht Stuttgart
Mobile:  [phone]           Geschaeftsfuehrer: Christian Kratzer
Web:     http://www.cksoft.de/
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[Christian Kratzer]

Hi,

On Thu, 28 Sep 2017, Jan Lundmark wrote:
<snipp/>
> Is there a way to assign fixed IP(v4) adresses in dhcpd.conf to clients based on their VLAN membership instead of their subnet?

once you have dhcp snooping setup you can do things like this:

cisco switch:

!
ip dhcp snooping vlan 101
!
interface GigabitEthernet1/0/1
  switchport mode access
  switchport access vlan 101
  ip dhcp snooping vlan 101 information option format-type circuit-id override string foo
!

interface GigabitEthernet1/0/2
  switchport mode access
  switchport access vlan 101
  ip dhcp snooping vlan 101 information option format-type circuit-id override string bar
!

dhcp.conf:

host foo {
     host-identifier option agent.circuit-id "foo";
     fixed-address 192.0.2.1;
}
host bar {
     host-identifier option agent.circuit-id "bar";
     fixed-address 192.0.2.2;
}


>
> Regards
>
> Jan
>
>
>
>
>

--
Christian Kratzer                   CK Software GmbH
Email:   [hidden email]               Wildberger Weg 24/2
Phone:   [phone] - 0       D-71126 Gaeufelden
Fax:     [phone] - 9       HRB 245288, Amtsgericht Stuttgart
Mobile:  [phone]           Geschaeftsfuehrer: Christian Kratzer
Web:     http://www.cksoft.de/
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[Doug Hughes]

3rd for Option 82. Most switches DHCP relay agent will support this via
a command. The problem I ran into with the ISC DHCP option 82 was that I
could do it based upon circuit-id (switch port) or on switch ID
(sometimes IP address of switch, sometimes configurable to mac, or
sometimes to hostname, usually configurable), but trying many different
ways I could never get it to use both at the same time.

If your use case is simple on a single switch, or multiple switches
where the switch port is unique, it should work just fine.



On 9/28/2017 5:58 AM, Patrick Trapp wrote:

> Seconding Christian's suggestion if your relay agent will support it.
>
> -----Original Message-----
> From: dhcp-users [mailto:[hidden email]] On Behalf Of Christian Kratzer
> Sent: Thursday, September 28, 2017 4:48 AM
> To: Users of ISC DHCP <[hidden email]>
> Subject: Re: VLAN and fixed IPs
>
> Hi,
>
> On Thu, 28 Sep 2017, Jan Lundmark wrote:
>>
>>
>> Hi,
>>
>> We have an application where we want the clients to  have fixed IPs and that the clients are all on the same subnet.
>> It is not practical for our application to use the MAC adresses of the clients.
>>
>> This configuration below will assign a somewhat fixed IP based on the VLAN  subnets but it is not exactly what we want.
>> The point is that we want each client to receive a fixed IP address based on their port in the switch.
> <snipp/>
>
> dhcp snooping on some switches is able to insert realay agent options into packets passing by even in pure l2 environments.
>
> You can then assign fixed ip based on option82 circuit-id or remote-id options.
>
> Greetings
> Christian
>

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[Christian Kratzer]

Hi,

On Thu, 28 Sep 2017, Doug Hughes wrote:

> 3rd for Option 82. Most switches DHCP relay agent will support this via
> a command. The problem I ran into with the ISC DHCP option 82 was that I
> could do it based upon circuit-id (switch port) or on switch ID
> (sometimes IP address of switch, sometimes configurable to mac, or
> sometimes to hostname, usually configurable), but trying many different
> ways I could never get it to use both at the same time.

yes isc cannot match both.

Generally you should have control over what values you provision into circuit-id or remote-id so you should be able to provision a sufficently unique value so you can get by with only matching one of them.

In an isp ptp fibre scenario I provision the customers lineid into option82 circuit-id.

> If your use case is simple on a single switch, or multiple switches
> where the switch port is unique, it should work just fine.

the trick is to design your network so that what you want is possible.


Greetings
Christian

--
Christian Kratzer                   CK Software GmbH
Email:   [hidden email]               Wildberger Weg 24/2
Phone:   [phone] - 0       D-71126 Gaeufelden
Fax:     [phone] - 9       HRB 245288, Amtsgericht Stuttgart
Mobile:  [phone]           Geschaeftsfuehrer: Christian Kratzer
Web:     http://www.cksoft.de/
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