Issue with DHCP Relay

[cnh93]

Hello,

I'm relatively new to networking and am studying for my CCNA using Packet Tracer. One of the lab requirements for my class is to set up a network where all departments except for one are suppose to pull down DHCP addresses from the server. So far, two of the departments are able to retrieve DHCP addresses, but the others are not. I'm using OSPF as the link-state routing protocol (we're instructed not to use EIGRP), which I'm not sure if that could be causing problems because the PCs that pull down DHCP addresses are able to ping the router closest to their network, but not their neighbors.

For the IP helper address, I've tried using the IP address of the DHCP server, the IP address of the serial interface facing the network, the serial interface facing away from the network, and the default gateway of both the PCs network and DHCP server's network. None of these have worked for me. 

I've also tried modifying the DHCP pool's default gateway from within the server configuration, but this hasn't worked either.

Any help would be greatly appreciated. I'm not looking for someone to do it for me, but rather explain what I'm doing wrong and what the correct course of action would be to fix it.

[Seb Rupik]

Hi there,

You need to ensure that a ping sourced from the interface where the ip helper-address command is configured can reach the DHCP server. The IP address specified in the ip helper-address address should be that of the DHCP servers interface. The DHCP server must have DHCP scopes defined for each of the subnets which specify it as the ip helper-address.

cheers,

Seb.

[Georg Pauwen]

Hello,

post the zipped Packet Tracer project (.pkt) file.

[cnh93]

Hi Georg,

Attached is the zipped .pkt file. For the record, I just changed the routing protocol to EIGRP just to see if the issue was stemming from the OSPF adjacencies (which it was not). 

Seb, I changed the ip helper-address to that of the DHCP server to no avail, and the PCs on the outside network are not currently able to ping the DHCP server.

[Georg Pauwen · Accepted solution]

Hello,

the problem was that you did not announce the local LAN interfaces/networks in EIGRP, so your networks could not even reach the DHCP server.

Attached the working file.

[cnh93]

Hi Georg,

Thank you so much for your help! I greatly appreciate it. Do you mind telling me what commands you used to announce the local networks in EIGRP? Did I miss an extra "network x.x.x.x x.x.x.x" for one of the networks, or is there an additional step that I overlooked? Just curious so that I can learn from my mistakes.

EDIT: spelling and clarity

Thank you again!

[Georg Pauwen]

Hello,

indeed, you 'forgot' to add network statements for all 192.168.x.x networks.

I actually used a shortcut:

network 0.0.0.0

This is a wildcard network statement that includes ALL networks configured on your router.