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Hi everybody.
Maybe I'm asking something previously answered. I configured my new iscp-dhcp-server (Ubuntu 16.04) to server requests from a network of APs. Those APs are connected to a Cisco switch, having 192.168.120.1/24 as primary address, and a secondary subnet with address 10.0.0.1/16 (yes, 16...). It has relay configured, just to send the dhcp requests to 192.168.120.20, a Windows machine. Today I have a Windows machine connected there, where I use the AP controller software, and TFTPD64, a thin software that works as a DHCP server. I configured there a range (10.0.0.10 -> 10.0.200.200) and everything works well, but it's Windows, then from time to time, I have to reboot the system. This is why I configured the new machine as 192.168.120.40/24, installed isc-dhcp-server package, and configured the following lines on /etc/dhcp/dhcpd.conf:
default lease-time 600; max-lease-time 7200;
subnet 10.0.0.0 netmask 255.255.0.0 { range 10.0.0.10 10.0.200.200; option subnet-mask 255.255.0.0; option routers 10.0.0.1; option domain-name-servers 8.8.8.8, 8.8.4.4; }
subnet 192.168.120.0 netmask 255.255.255.0 { }
When I start the server, I only see it trying to answer requests using network 192.168.120.0, then saying "no free leases", and not serving any 10.0.0.0/16 address.
Now I'm living with TFTPD64, but I plan to move that to a better solution. Does anybody know about this configuration? Is there something I'm doing wrong? Thanks a lot in advance, and best regards.
-- HeCSa
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Hi Hernan,
Could you please post the Cisco Switch's relevant configuration, also? Including the VLAN interfaces serving the 10.0.0.0/16 network. By the way, does this switch have conectivity with your dhcp server? This is mandatory for the DHCP relay to work, as the relay agent needs to forward DHCP messages for clients in unicast to the DHCP server; and the reverse path must be available also, once you're checking the direct path, give some time checking this also. _______________________________________________
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Also, if you are intending for addresses to be made available from both of the subnets, I believe you may need to define those pools as a shared network. Look up shared-network
in your handy DHCP documentation, but I would wonder if something like this would make a difference:
default lease-time 600;
max-lease-time 7200;
shared-network Combined-pools {
subnet 10.0.0.0 netmask 255.255.0.0 {
range 10.0.0.10 10.0.200.200;
option subnet-mask 255.255.0.0;
option routers 10.0.0.1;
option domain-name-servers 8.8.8.8, 8.8.4.4;
}
subnet 192.168.120.0 netmask 255.255.255.0 {
}
}
Or, so be more generic
shared-network shared-network-label
{
subnet1 x.x.x.x netmask 255.x.x.x
{
} (to close subnet1)
subnet2 y.y.y.y netmask 255.y.y.y
{
} (to close subnet2)
} (to close the shared-network declaration)
Hi Hernan,
Could you please post the Cisco Switch's relevant configuration, also? Including the VLAN interfaces serving the
10.0.0.0/16 network.
By the way, does this switch have conectivity with your dhcp server? This is mandatory for the DHCP relay to work, as the relay agent needs to forward DHCP messages for clients in unicast to the DHCP server; and the reverse path must be available also, once
you're checking the direct path, give some time checking this also.
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Hi José,
Today, I have a Windows machine running a DHCP server, with IP address 192.168.120.20/24, and serving DHCP address range 10.0.0.10 -> 10.0.200.200. Then, I can assume that my Cisco switch is working just fine. It's a soho switch, so it has only "secondary subnets", a concept that may sound like vlans, but are not. But this is working fine.
Thanks, and best regards,
HeCSa.
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On May 20, 2016 4:58:23 PM EDT, Hernan Saltiel < [hidden email]> wrote:
Hi everybody.
Maybe I'm asking something previously answered. I configured my new iscp-dhcp-server (Ubuntu 16.04) to server requests from a network of APs. Those APs are connected to a Cisco switch, having 192.168.120.1/24 as primary address, and a secondary subnet with address 10.0.0.1/16 (yes, 16...). It has relay configured, just to send the dhcp requests to 192.168.120.20, a Windows machine. Today I have a Windows machine connected there, where I use the AP controller software, and TFTPD64, a thin software that works as a DHCP server. I configured there a range (10.0.0.10 -> 10.0.200.200) and everything works well, but it's Windows, then from time to time, I have to reboot the system. This is why I configured the new machine as 192.168.120.40/24, installed isc-dhcp-server package, and
configured the following lines on /etc/dhcp/dhcpd.conf:
default lease-time 600; max-lease-time 7200;
subnet 10.0.0.0 netmask 255.255.0.0 { range 10.0.0.10 10.0.200.200; option subnet-mask 255.255.0.0; option routers 10.0.0.1; option domain-name-servers 8.8.8.8, 8.8.4.4; }
subnet 192.168.120.0 netmask 255.255.255.0 { }
When I start the server, I only see it trying to answer requests using network 192.168.120.0, then saying "no free leases", and not serving any 10.0.0.0/16 address.
Now I'm living with TFTPD64, but I plan to move that to a better solution. Does anybody know about this configuration? Is there something I'm doing wrong? Thanks a lot in advance, and best regards.
-- HeCSa
dhcp-users mailing list
[hidden email]
https://lists.isc.org/mailman/listinfo/dhcp-users
Since both networks are on the same wire, I believe that you need to place your two subnet statements within a shared-network statement.
--
Sent from my Android device with K-9 Mail. Please excuse my brevity. _______________________________________________
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Yes, that's it. The concept of dhcp relays is bound to the concept of network segmentation. If your network is not segmented, you need shared networks.
Be advised, however, that if you, later, need to offer DHCP also on the 192.168.200.0/24 network, you'll need a configuration much more elaborated. _______________________________________________
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On 21 May 2016, at 3:09, Hernan Saltiel wrote:
> Today, I have a Windows machine running a DHCP server, with IP
> address [192.168.120.20/24]( http://192.168.120.20/24), and serving
> DHCP address range 10.0.0.10 -> 10.0.200.200. Then, I can assume that
> my Cisco switch is working just fine. It's a soho switch, so it has
> only "secondary subnets", a concept that may sound like vlans, but are
> not. But this is working fine.
I expect you'll need a "shared-network" declaration to let dhcpd know
that
the two subnets belong together.
shared-network whatever {
subnet 10.0.0.0 netmask 255.255.0.0 {
# details ...
}
subnet 192.168.120.0 netmask 255.255.255.0 {
# details ...
}
}
I hope this helps.
Best regards,
Niall O'Reilly
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Hernan Saltiel < [hidden email]> wrote:
> I configured my new iscp-dhcp-server (Ubuntu 16.04) to server requests from a network of APs.
> Those APs are connected to a Cisco switch, having 192.168.120.1/24 as primary address, and a secondary subnet with address 10.0.0.1/16 (yes, 16...). It has relay configured, just to send the dhcp requests to 192.168.120.20, a Windows machine.
Am I missing something here ? In a later message you indicated that this is a basic switch, so as I see it, the server and clients are on the same network - so you don't need a relay agent on the switch.
As others have pointed out, and you've verified works, you just need a shared network construct on the server to make it work.
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