3524 not letting DHCP pass

[rryan]

I've got a couple of 3524xl's that will not allow workstations to get a dhcp address. If the computer is assigned a static IP, it works great. The 3524 is connected to a 6509 via gbic. Workstations connected to 6509 rj-45 get dhcp ok.

Anybody ever seen this?

Randy

[mjoubert1]

Sounds like these things are not forwarding the DHCP client broadcast to the server or they are timing out. A network monitor or sniffer would be able to help you isolate point of failure during IP Address negotiation. Also, it would not hurt to check the logs on the server for the DHCP scope you provisioned to the 3524s subnet.

[rryan]

A sniffer on the 3524 doesn't show any type of dhcp request. Other workstations on the same vlan, on different switches, obtain addersses ok. Server logs show no activity at all from workstation connected to 3524, but does show normal activity from other devices.

[mjoubert1]

More specifically, if the initial broadcasts are not being forwarded (routers don't forward by default), the you need to look at assigning an ip helper-address command.

From what I can tell, the workstations are not on the same subnet as the DHCP servers. So you will have to place in your config a "ip helper-address xxx.xxx.xxx.xxx" to allow the 6509 to take the broadcast and turn it into a unicast message directed to the DHCP server.

Place this statement on the GBIC interface going from the 6509 to the 3524.

[rryan]

An IP-HELPER ADDRESS is entered globally and other stations get dhcp ok

Thanks

[raju]

Randy,

Just enable the portfast on the ports in 3524 and give a try.

Thanks.

[rryan]

Portfast is enabled on all the fastethernet ports.

Thanks

[glen.grant]

Can you ping the dhcp server from the 3524 ?? Are the NIC's on the clients setup for dhcp ?? Seeing that you say you have portfast turned on , i would also turn trunking and channeling off too . I have seen in a couple of cases where this caused a problem in time sensative apps like IPX . If you had a sniffer on the switch and you had it spanned correctly and you say you don't see the request then the clients are not passing the request out and it isn't a switch problem . Did you have the sniffer directly on the 3524's when you looked at it , if not I would start there and see if you see any of the dhcp requests. Are the 3524's in the same vlan as the users that are directly attached to the 6509 ? Maybe if you post the configs we can see something else .