# DHCP Traffic Not Traversing VLANs



## LeeNetworX (Apr 29, 2008)

Hello all. Sorry for my first post here being a question, but I was just searching Google and stumbled upon this forum.

We have been using our Catalyst 3560 for providing DHCP services to two subnets, both of which are VLANs on the switch. We just switched over to using a Windows DHCP server. The DHCP server is sitting in one of the two VLANs that receives address via DHCP. Hosts in that VLAN are not having any issues getting IPs. The hosts in the other VLAN, however, cannot. We setup an IP-Helper for that VLAN but it doesn't seem to be working. :upset:

We tried assigning a host a static IP in that VLAN, and it can ping the DHCP server, so it seems routing is working. SH INT VLAN shows up/up. It also shows " Received 0 broadcasts (0 IP multicast) " which seems to verify that DHCP traffic isn't making it in or out. Tried rebooting the switch.

Does anyone have any ideas? Any help would be most appreicated. Thanks for your time.

Here's the snippet for the VLAN config:

interface Vlan86
description ** iLO **
ip address 10.7.86.1 255.255.255.0
ip helper-address 10.7.80.2


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## johnwill (Sep 26, 2002)

Suggestion from: http://www.experts-exchange.com/OS/Microsoft_Operating_Systems/Server/Q_22533966.html



> What you would do is setup multiple scopes on your dhcp server. Then on the router that is connected to all of these vlan’s or a Layer3 switch you would need to setup an ip helper-address. So it would look like this command.
> interface Vlan10
> description VLAN 10
> ip address 10.10.10.1 255.255.255.0
> ...


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## LeeNetworX (Apr 29, 2008)

That's what I have in the switch config; please see the snippet I included in my original post. :wink:

The problem is that it's not working. The switch itself seems to be consuming the DHCP requests sent by the clients. Here's a debug trace:

000749: 01:50:33: IP: s=0.0.0.0 (Vlan86), d=255.255.255.255, len 576, rcvd 2
000750: 01:50:33: UDP src=68, dst=67
000751: 01:50:33: IP: s=0.0.0.0 (Vlan86), d=255.255.255.255, len 576, stop process pak for forus packet
000752: 01:50:33: UDP src=68, dst=67
000753: 01:50:33: IP: s=0.0.0.0 (Vlan86), d=255.255.255.255, len 576, rcvd 2
000754: 01:50:33: UDP src=68, dst=67
000755: 01:50:33: IP: s=0.0.0.0 (Vlan86), d=255.255.255.255, len 576, stop process pak for forus packet
000756: 01:50:33: UDP src=68, dst=67
000757: 01:50:33: IP: s=0.0.0.0 (Vlan86), d=255.255.255.255, len 576, rcvd 2
000758: 01:50:33: UDP src=68, dst=67
000759: 01:50:33: IP: s=0.0.0.0 (Vlan86), d=255.255.255.255, len 576, stop process pak for forus packet
000760: 01:50:33: UDP src=68, dst=67


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