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

[Daniel Graham]

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.

Thanks!

[Rajeev Sharma]

Hey Daniel,

I believe its a good candidate for TAC case.

Regards,

RS.

[pavel_kotelva]

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!

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Best regards,

Pavel Kotelva

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Best regards,

Pavel Kotelva

[Daniel Graham]

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.

-dan

[pavel_kotelva]

Hi, Daniel,

Thanks a lot!