Multiple subnets across different vlans
Joshua Beard
josh at hewbert.com
Sat Jul 9 07:45:48 UTC 2011
Thanks for the responses. I've had 'authoritative' set since deploying the server. As far as the shared-network, I didn't have that configured for very long.
From the looks of it, it's limited to a handful of clients that are giving the 'wrong network' error, and they're all on the same subnet. In fact, the logs are pretty full of a handful of clients continuously making requests. For example:
Jul 9 01:39:17 ns1 dhcpd: DHCPREQUEST for 172.30.99.41 (172.30.112.121) from 00:50:41:72:67:2e via eth0: wrong network.
Jul 9 01:39:17 ns1 dhcpd: DHCPNAK on 172.30.99.41 to 00:50:41:72:67:2e via eth0
Jul 9 01:39:17 ns1 dhcpd: DHCPREQUEST for 172.30.99.24 (172.30.112.121) from 00:50:41:72:63:be via eth0: wrong network.
Jul 9 01:39:17 ns1 dhcpd: DHCPNAK on 172.30.99.24 to 00:50:41:72:63:be via eth0
Jul 9 01:39:18 ns1 dhcpd: DHCPREQUEST for 172.30.99.10 (172.30.112.121) from 00:50:41:72:65:19 via eth0: wrong network.
Jul 9 01:39:18 ns1 dhcpd: DHCPNAK on 172.30.99.10 to 00:50:41:72:65:19 via eth0
Jul 9 01:39:19 ns1 dhcpd: DHCPREQUEST for 172.30.99.62 (172.30.112.121) from 00:50:41:72:5d:01 via eth0: wrong network.
Jul 9 01:39:19 ns1 dhcpd: DHCPNAK on 172.30.99.62 to 00:50:41:72:5d:01 via eth0
Jul 9 01:39:21 ns1 dhcpd: DHCPREQUEST for 172.30.99.41 (172.30.112.121) from 00:50:41:72:67:2e via eth0: wrong network.
Jul 9 01:39:21 ns1 dhcpd: DHCPNAK on 172.30.99.41 to 00:50:41:72:67:2e via eth0
Jul 9 01:39:21 ns1 dhcpd: DHCPREQUEST for 172.30.99.24 (172.30.112.121) from 00:50:41:72:63:be via eth0: wrong network.
I don't know the state of those current machines, but I would've assumed they were sleeping. Could some sort of wake-on-lan feature be continuously making requests?
>> Is 172.30.112.121 the address of the DHCP server?
Yes, this is the DHCP server.
Another question, if I may ask without starting a new topic, and I think I already know the answer. Along with DHCP, I migrated DNS from a Windows server to a Linux box running BIND. I did a zone transfer for this migration. Things seem mostly happy, but a lot of clients produce this in the dhcpd logs:
Jul 9 01:38:06 ns1 dhcpd: Forward map from MS40102S44572.dsdk12.schoollocal. to 172.30.133.41 FAILED: Has an A record but no DHCID, not mine.
Obviously, they were leased with the old dhcp server and their A records were migrated in the zone transfer. I'm using dynamic dns updates here, and from what I've seen, these clients fail to get an address if there's already a DNS record for them. FWIW, this is a k-12 school district and most everyone's gone for the summer, so if I have to, I can just remove all of the DNS records for the dynamic hosts. Any suggestions here?
As far as the 'wrong network' goes, it sounds like I need to just wait it out to clean itself up.
Thanks,
Josh
On Jul 9, 2011, at 1:21 AM, Glenn Satchell wrote:
> Yep, looks like shared-network is wrong for your network layout.
>
> You could also an add "authoritative" statement to the global scope, then dhcpd will send a DHCPNAK to those wrong addresses and they will go back to DHCPDISCOVER and get a new address on the correct subnet.
>
> regards,
> -glenn
>
> On 07/09/11 14:23, Chris Buxton wrote:
>> Don't use shared networks for logical networks on two separate VLANs. A shared network (aka multinet or Windows superscope) is when both subnets are on the same VLAN (or the same physical network in the absence of VLANs).
>>
>> You're getting a DHCP request for an address on one VLAN, but then in parens it lists an address in the other VLAN. Is 172.30.112.121 the address of the DHCP server? I believe you'll see this is from having previously had a shared-network statement wrapped around your subnet declarations. Get rid of the shared-network declaration, and then reboot all your client machines (or otherwise cause them to renew their DHCP leases). Once they all have correct addresses, you shouldn't see any more of these messages, if I'm right.
>>
>> Regards,
>> Chris Buxton
>> BlueCat Networks
>>
>> On Jul 8, 2011, at 5:57 PM, Joshua Beard wrote:
>>
>>> Hello,
>>>
>>> We've recently migrated from dhcp services on a Windows box to using ISC dhcpd on a Linux box. We have a number of different subnets on their own respective vlans.
>>>
>>> Unfortunately, I'm having an issue where using shared-network { } causes clients on different subnets get an address from the wrong subnet. If I drop shared-network, their addressed are assigned *correctly*, but I get a "wrong network" message in the logs:
>>> Jul 6 16:20:11 ns1 dhcpd: DHCPREQUEST for 172.30.99.62 (172.30.112.121) from 00:50:41:72:5d:01 via eth0: wrong network.
>>>
>>> I believe the switches are configured correctly, as it worked as expected on the Windows machines and I get these in the dhcpd log:
>>> Jul 6 20:38:55 ns1 dhcpd: DHCPACK on 172.30.101.145 to 00:25:4b:b8:27:7e (HS01303S4418) via 172.30.96.1<--
>>>
>>> Here's an example of the config:
>>>
>>> shared-network douglas {
>>>
>>> include "/etc/dhcp3/dhcpd.reservations.conf";
>>>
>>> subnet 172.30.112.0 netmask 255.255.240.0 {
>>>
>>> range 172.30.115.1 172.30.127.254;
>>> option subnet-mask 255.255.240.0;
>>> option broadcast-address 172.30.112.255;
>>> option routers 172.30.112.2;
>>>
>>>
>>> }
>>>
>>> subnet 172.30.96.0 netmask 255.255.240.0 {
>>>
>>> range 172.30.99.1 172.30.111.254;
>>> option subnet-mask 255.255.240.0;
>>> option broadcast-address 172.30.96.255;
>>> option routers 172.30.96.1;
>>>
>>>
>>> }
>>> }
>>>
>>> With this example (using shared-network), clients on the second subnet will get an address belonging to the first. If I drop the 'shared-network', each subnet assigns correctly, but the "wrong network" error appears on the logs. I should note that this dhcp server belongs to the first subnet here and only has eth0 configured.
>>>
>>> Any hint in the right direction is much appreciated.
>>>
>>> Thanks,
>>> Josh
>>>
>>>
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