DHCP Problem(IP_Helper)

[hkkris123]

Hi Guys,

            My topology has got 2 "cisco 1921" routers (which are interconnected using x-over cable ans static IP has been used and both are pinging), Two routers are named as say R1 and R2.  Where R1 is configured as DHCP server and on R2 side i connected a PC to reterive IP address from the R1(DHCP server), but its not getting it. I know routers wont transmit broadcast address, so i used "ip helper address command" on R2 (Fa0/0 interface) connected to the PC, but still no luck . Am i missing anything over here? Help Please!!!

Thanks,

Hari

[s.kanth · Accepted solution]

Hi Hari,

What type of cable is used in between router2 to PC ? (should be cross-over cable)

or enable auto MDIX on interface fa0/0 of the router R2.

Thanks

Sri

[Richard Burts · Accepted solution]

Usually I would agree that checking on the cabling would be a good thing to do. But since Hari says in the original post that the routers are connected by cross over cable and says that they are pinging, we do not need to be concerned about cabling or basic IP connectivity.

My guess about the problem is that the ip helper-address is not configured correctly. If Hari will post the addresses used and post the configuration of the ip helper-address we could evaluate whether this is the problem.

If it turns out that the ip helper-address is configured correctly then my next guess would be that the DHCP on R1 is not correctly configured. If Hari would post that part of the configuration we could check on that.

HTH

Rick

[hkkris123]

Hi Guys,

          Thanks for the help!!! It works now .

@Sri - MDIX has already been enabled, as saying it, i was using X-Over cable to connect it.

@Rick - Yeah u are right, it was wrong command "ip helper-addr", wrong ip has been assigned to it, thats why .

But one more doubt, can we assign multiple ip addresses on "default-router" command? In cisco website it says we can use it, i tried to find some example but no luck. Sorry for such a pain in the neck.

Thanks once again, much appreciate it!!!

Cheers,

Hari

[cadet alain]

Hi,

Yes I think you can configure multiple default-gateways  but I would use HSRP or VRRP or even GLBP( if you want load-balancing) for high availability and send the VIP as the default gateway instead because you can track the reachability to outside with these features that you can't do with the multiple default gateways as far as I know.

Also worth to take a look at this doc from Windows for multiple default gateways and why it may not work with a non Windows dhcp server:  http://blog.palehorse.net/2009/08/24/using-windows-7-with-multiple-gateways-and-dhcp/

Regards.

Alain.