# HELP - routine update broke dhcp server - SOLVED

## Moriah

I updated the machine that runs my dhcp server, and now dhcp is broken.  The old version was 4.2.4-P2 installed on Oct 16 14:18; the new version is actually the same: net-misc/dhcp-4.2.4_p2, so it must be a library or something that has changed.  I also updated the kernel from 2.6.37-gentoo-r4 to 3.5.7-gentoo, so maybe that has something to do with it.  I re-emerged net-misc/dhcp just to be sure, but it still does not work.

When a machine tries to get a dhcp address, the server's log shows:

```

Mar 22 21:27:20 daniel dhcpd: DHCPREQUEST for 192.168.3.146 from 8c:fa:ba:a4:d8:94 via eth0: wrong network.

Mar 22 21:27:20 daniel dhcpd: DHCPNAK on 192.168.3.146 to 8c:fa:ba:a4:d8:94 via eth0

Mar 22 21:27:22 daniel dhcpd: DHCPREQUEST for 192.168.3.146 from 8c:fa:ba:a4:d8:94 via eth0: wrong network.

Mar 22 21:27:22 daniel dhcpd: DHCPNAK on 192.168.3.146 to 8c:fa:ba:a4:d8:94 via eth0

Mar 22 21:27:24 daniel dhcpd: DHCPREQUEST for 192.168.3.146 from 8c:fa:ba:a4:d8:94 via eth0: wrong network.

Mar 22 21:27:24 daniel dhcpd: DHCPNAK on 192.168.3.146 to 8c:fa:ba:a4:d8:94 via eth0

Mar 22 21:27:28 daniel dhcpd: DHCPDISCOVER from 8c:fa:ba:a4:d8:94 via eth0

Mar 22 21:27:28 daniel dhcpd: DHCPOFFER on 192.168.1.24 to 8c:fa:ba:a4:d8:94 via eth0

Mar 22 21:27:30 daniel dhcpd: DHCPDISCOVER from 8c:fa:ba:a4:d8:94 via eth0

Mar 22 21:27:30 daniel dhcpd: DHCPOFFER on 192.168.1.24 to 8c:fa:ba:a4:d8:94 via eth0

Mar 22 21:27:32 daniel dhcpd: DHCPDISCOVER from 8c:fa:ba:a4:d8:94 via eth0

Mar 22 21:27:32 daniel dhcpd: DHCPOFFER on 192.168.1.24 to 8c:fa:ba:a4:d8:94 via eth0

Mar 22 21:27:37 daniel dhcpd: DHCPDISCOVER from 8c:fa:ba:a4:d8:94 via eth0

Mar 22 21:27:37 daniel dhcpd: DHCPOFFER on 192.168.1.24 to 8c:fa:ba:a4:d8:94 via eth0

```

And a tcpdump packet trace shows:

```

daniel ~ # tcpdump -i eth0 not port 5094 and host daniel and not port ssh

tcpdump: verbose output suppressed, use -v or -vv for full protocol decode

listening on eth0, link-type EN10MB (Ethernet), capture size 65535 bytes

21:13:37.675654 IP 192.168.1.11.bootps > 255.255.255.255.bootpc: BOOTP/DHCP, Reply, length 300

21:13:39.624635 IP 192.168.1.11.bootps > 255.255.255.255.bootpc: BOOTP/DHCP, Reply, length 300

21:13:41.844206 IP 192.168.1.11.bootps > 255.255.255.255.bootpc: BOOTP/DHCP, Reply, length 300

21:13:46.387745 IP 192.168.1.11.bootps > 192.168.1.24.bootpc: BOOTP/DHCP, Reply, length 300

21:13:48.193729 IP 192.168.1.11.bootps > 192.168.1.24.bootpc: BOOTP/DHCP, Reply, length 300

21:13:50.923229 IP 192.168.1.11.bootps > 192.168.1.24.bootpc: BOOTP/DHCP, Reply, length 300

21:13:55.690646 IP 192.168.1.11.bootps > 192.168.1.24.bootpc: BOOTP/DHCP, Reply, length 300

21:14:03.931324 IP 192.168.1.11.bootps > 192.168.1.24.bootpc: BOOTP/DHCP, Reply, length 300

21:14:12.167349 IP 192.168.1.11.bootps > 192.168.1.24.bootpc: BOOTP/DHCP, Reply, length 300

```

Because udev was also updated as part of this update, I cannot revert back to the old kernel.    :Sad: 

Any ideas what is wrong?    :Question: 

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## gerdesj

At a first guess you have another change to deal with.  A machine that had an address from your DHCP server in the network 192.168.3/24 is now requesting one 

on 192.168.1/24 which your DHCP server is not equipped to deal with.

We'll need far more details to fix this for you:

IP address of DHCP server

All IPs of DHCP server

What subnets are available on your network (real or VLANd in some way)

Is DHCP relay in use

That should be enough to start with.

Cheers

Jon

PS It is unlikely that a kernel update or any other update broke this - but not impossible, something else changing is far more likely

 *Moriah wrote:*   

> I updated the machine that runs my dhcp server, and now dhcp is broken.  The old version was 4.2.4-P2 installed on Oct 16 14:18; the new version is actually the same: net-misc/dhcp-4.2.4_p2, so it must be a library or something that has changed.  I also updated the kernel from 2.6.37-gentoo-r4 to 3.5.7-gentoo, so maybe that has something to do with it.  I re-emerged net-misc/dhcp just to be sure, but it still does not work.
> 
> When a machine tries to get a dhcp address, the server's log shows:
> 
> ```
> ...

 

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## Moriah

Its not nearly as difficult as you expected.  The machine requesting the dhcp address was on a different network segment previously, as it is a portable device -- an iPad, no less.  It was on a different wireless access point previously, and so the 192.168.3.x address was what it was assigned there.  The dhcp server that is having a problem is on a 192.168.1.x network.  Simple, see?    :Cool: 

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