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DHCP host routes not added when using IP Unnumbered with DHCP relay

With the following setup, DHCP host routes are added until lease expiration, they then disappear and are not re-populated.

6500 WS-SUP720-3B with MSFC3 (Redundant in sso mode)

s72033_rp-PK9SV-M Version 12.2(18)SXD7b

FlexWAN - WS-X6182-2PA with PA-A3-OC3-SMI

service dhcp
ip dhcp-server y.y.y.y

interface loopback 1
ip address x.x.x.x

interface ATMX/X/X.x
ip unnumbered loopback1
ip helper-address y.y.y.y

show ip route dhcp

S   z.z.z.z/32 is directly connected, ATMX/X/X.x

After 15 minute DHCP lease this route is removed.

Once this route has been removed, nothing I have tried will make it re-populate.

I have removed and re-added loopback interface, removed and re-inserted FlexWAN/PA, reload, fail-over to standby SUP.

However if I re-test 24 hours later, the DHCP host route will be added again, but only until lease expiration and the same behavior repeats.

I did a debug dhcp server events and debug dhcp server packet and I saw forwards to DHCP server and I also saw replies back to client.

Any direction or thoughts are appreciated.



Hey Daniel,I believe its a

Hey Daniel,

I believe its a good candidate for TAC case.



Community Member

Hi, Daniel,I have the same

Hi, Daniel,

I have the same problem on WS-C6506-E with WS-SUP720-3BXL running 12.2(33)SXI6: ip unnumbered+dhcp relay configuration didn't see the unicast DHCP_RENEW & DHCP_ACK packets. So, 6500 didn't renew the route until broadcast DHCP request comes, while client and access switch process unicast DHCP packets correctly.


Have you found a workaround of this problem?


Thanks for all advices!


Best regards,

Pavel Kotelva


Best regards,

Pavel Kotelva

Community Member

Unfortunately I have not

Unfortunately I have not found a solution, I was forced to move to a different platform in the meantime. It would be great to move back to the 6500 if a solution is found.


Community Member

Hi, Daniel, Thanks a lot!

Hi, Daniel,


Thanks a lot!

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