DHCP Server Debug Errors - What do they mean?

[Anonymous]

While responding to an issue for a client that had a Polycom IPphone that would't get an IP address, I enabled DHCP SERVER DEBUG.  The Polycom phone issue was attributed to an auto negotiation issue, but I noted the following in the DHCP SERVER DEBUG and wondered what it meant and why I was getting it.

2014.10.23 10:01:38 DHCP.SERVER Discarding message, no available pools: (Xid = 1377af1a) on 10.0.0.0/255.255.255.0 from 74:86:7A:29:47:77

2014.10.23 10:01:38 DHCP.SERVER No Reply required

2014.10.23 10:02:14 DHCP.SERVER Error, the minimum message size from RFC 1542 is 300 Bytes

2014.10.23 10:02:14 DHCP.SERVER Discarding message, no available pools: (Xid = a607fd04) on 10.0.0.0/255.255.255.0 from 00:00:00:00:00:00

2014.10.23 10:02:14 DHCP.SERVER No Reply required

This is on a NV1335poe Router running ADTRAN, Inc. OS version R10.9.4.E.

The DHCP configuration is as follows:

ip dhcp database local

ip dhcp excluded-address 10.10.11.1 10.10.11.99

ip dhcp excluded-address 10.10.11.201 10.10.11.254

!

ip dhcp pool "VOICE"

  network 10.10.11.0 255.255.255.0

  domain-name "voice.client.local"

  dns-server 10.10.11.1

  default-router 10.10.11.1

  lease 3

  ntp-server 50.7.68.4

  timezone-offset -5:00

!

Thank you,

Chad

[ss_daveh]

Looks to be the device requesting DHCP is doing so on a 10.0.0.0 /24 network which is not within the subnet of the DHCP pool you have created. I've seen this when there is a LAN network address on the router of a different subnet it is communicating with or if there are multiple VLANS on the LAN and you are getting broadcast from a different network.

I would check and make sure that you do have a 10.10.11.1 interface and also to run a "debug arp" along with the "debug ip dhcp server" while a device is requesting a network address. This will show you which device is sending the ARP as it may be a switch or other device and not the phone. Also, check in the phone to make sure there is no default gateway or VLAN ID in the advanced settings as this will sometimes override which network it is requesting an address from.