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Cisco Bug: CSCut30235 - Delay the transmission of discover from ASR9000 dhcp proxy

Last Modified

Feb 13, 2018

Products (1)

  • Cisco ASR 9000 Series Aggregation Services Routers

Known Affected Releases

5.1.3.BASE

Description (partial)

Symptom:
> Working in DHCP Proxy, it appears that when the 9K processes a Discover and adds the Release it is sending the Discover almost immediately(5ms to be exact) after the Release which doesn't give customer's redundant DHCP servers enough time to process the actual Release and make that IP "available" thus causing the DHCP server to change the IP during re-assignment.

Conditions:
> DHCP servers are in a cluster and use DHCP Failover so it takes a little time for information to sync.  
In a normal DHCP client Release(without the 9K), there is usually at least some delay before a Discover is sent which gives the DHCP servers plenty of time to process but since the 9K is now adding a Release every time there is a Discover and it is immediate, that appears to be where the problem is.  
We tested this in house with a manually sent DHCP Release, waited 10 seconds and then a Discover.  The IP did not change.
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