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IP Helper-Address Not Forwarding DHCP Requests to a Different Site

alexellington
Level 1
Level 1

I have 2 sites, one router & one switch per site. There is connectivity between the two sites on the fiber interface. The routing method is EIGRP and is configured correctly. The routes are being updated in the routing table and I can ping any IP address from either side (including the remote DHCP server).

Here is my problem: connecting on the access port of the switch I am unable to get an IP address from the DHCP server on the other site. I have the interface for the VLAN to be using an ip helper-address on the opposite side andddd nothing.

I thought maybe it was because it was sharing the same IP pool, so I created a pool that matched the subnet to hand out leases. Still not working.

I've attached the full devices config with redacted passwords on the site to site setup here with Router1, Switch1, Router2 & Switch2. Mind you, everything else in the configuration works minus the DHCP relay.

If someone could tell me why I cannot get my ip helper-request to forward into a remote site, I would greatly appreciate it and probably owe you a beer.

1 Accepted Solution

Accepted Solutions

balaji.bandi
Hall of Fame
Hall of Fame

If the VLAN 10 from Local Site not getting from remote side Router DHCP  pool from 10.20.10.0/24

quick fix is  as below  test and let me know.

interface GigabitEthernet0/0.10
encapsulation dot1Q 10
ip address 10.20.10.1 255.255.255.0

no ip helper-address 10.20.10.1

ip helper-address 62.22.247.169  <-- add this and test it

Note : there are other things in DHCP exclude list to be added , i was just only commented based on the issue

BB

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View solution in original post

7 Replies 7

M02@rt37
VIP
VIP

Hello @alexellington,

Does R1 know the route towards 10.20.30.1 ?

Try a ping from Router 1 towards 10.20.30.1 source with 10.10.30.1 (ip of Gi0/0.30) 

Does R2 kwow the route towards 10.10.30.1? 

Same test and check on Router 2 adjusting IP dest and source for ping.

Best regards
.ı|ı.ı|ı. If This Helps, Please Rate .ı|ı.ı|ı.

balaji.bandi
Hall of Fame
Hall of Fame

If the VLAN 10 from Local Site not getting from remote side Router DHCP  pool from 10.20.10.0/24

quick fix is  as below  test and let me know.

interface GigabitEthernet0/0.10
encapsulation dot1Q 10
ip address 10.20.10.1 255.255.255.0

no ip helper-address 10.20.10.1

ip helper-address 62.22.247.169  <-- add this and test it

Note : there are other things in DHCP exclude list to be added , i was just only commented based on the issue

BB

***** Rate All Helpful Responses *****

How to Ask The Cisco Community for Help

This resolved the problem, thanks!

I send you message check it 

Hello
You don't mention what hardware/software you are running for eigrp, however older ios software by default uses automatic summarization, which your case negates disconnected classful subnets (10.0.0.0/8) if you disable this feature you will be able to advertise the correct classless subnets by specifying "no auto-summary" under the eigrp routing stanza and then append the more specific eigrp interfaces.

example:
dhcp rtr
router eigrp 100

no auto-summary
network  62.22.247.169 0.0.0.0
network 10.100.1.254 0.0.0.0
network 10.10.10.1 0.0.0.0
network 10.10.20.1 0.0.0.0
network 10.10.30.1 0.0.0.0
no network 10.0.0.0
no network 62.22.247.0 0.0.0.255

rtr
router eigrp 100
no auto-summary
network  62.22.247.170 0.0.0.0
network 10.200.1.254 0.0.0.0
network 10.20.10.1 0.0.0.0
network 10.20.20.1 0.0.0.0
network 10.20.30.1 0.0.0.0
no network 10.0.0.0
no network 62.22.247.0 0.0.0.255

interface GigabitEthernet0/0.10
encapsulation dot1Q 10
ip address 10.20.10.1 255.255.255.0
ip helper-address 62.22.247.169


Please rate and mark as an accepted solution if you have found any of the information provided useful.
This then could assist others on these forums to find a valuable answer and broadens the community’s global network.

Kind Regards
Paul

Thanks for the information!

I don't see anything in config wrong so

As other suggestions check the route is known in dhcp local router 

And check if there is FW (or any Acl) drop unicast udp 67 traffic

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