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New Member

DHCP problem

Im encountering problem on DHCP for my clients residing on building connected to our main HQ on fiber. We have set-up the scopes for each sites and it works well with users connected to us using Frame relay and point-to-point lease circuit.

We have some users connected using fiber and using 2950's (2 port 100 base FX) and 2924 cisco switches (2 port 100 base FX).

Do i have to enable something from these switches ? something like "IP helper-address XXXXX" on the routers

  • Other Network Infrastructure Subjects
New Member

Re: DHCP problem

Yes, you will have to use the Ip helper address statement in order to service cliecnts on different networks/subnets.

New Member

Re: DHCP problem

I have done that for our point to point lease line and frame relay sites and DHCP works fine.

My question is whether do I have to enable any of that kinds of command on our fiber switches. By the way, there is no fancy configuration on my switches. Just the default VLAN for my remote management and monitoring.

Cisco Employee

Re: DHCP problem

Have you enabled spanning-tree portfast on all your client ports?

Make sure you have not disabled dhcp service(it's enabled by default). If you have disabled it, you can enable using "service dhcp" command from config mode.

If this does not help, try capturing a sniffer trace and decode the trace. The following page should help as well

New Member

Re: DHCP problem

Thank you. Spanning-tree portfast was diasbled. It is enable now. Where should I enable "service DHCP" ? On the rrouter or the switch ?

I know I have to disable "span-tree portfast" on ports where hubs and switches will be connected too. I also have some users connected to hubs and the hubs hang off the switch. Will it work if the hub hanging off the switch is a different model ? other than Cisco ?

New Member

Re: DHCP problem

Different models should work as long as you the ports that have the different manufactures devices are operational.

"service dhcp" would be enabled on the router.

This enables the DHCP server on the router.

Are you using the Router to work as the DHCP server?

Have you tried hard setting one of the client machines with an ip address, and then attempting to ping the DHCP server?

This would help determine if IP traffic can travel to and from the clients and the DHCP server.

If you can you might want to look at DHCP server logs to see if they see any requests from the clients.