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Cisco Bug: CSCtg95381 - Traffic may punt to CPU because uRIB is not installed

Last Modified

Aug 20, 2017

Products (3)

  • Cisco Nexus 7000 Series Switches
  • Cisco Nexus 7000 10-Slot Switch
  • Cisco Nexus 7000 18-Slot Switch

Known Affected Releases

5.0(2)

Description (partial)

Symptom:
Nexus 7000 may punt traffic to CPU; so that the traffic may experience random delay or drop.

Further looking, ARP is learned and FIB adjacency is in FIB adjacency table.

Conditions:
The problem is caused by race condition. Some hosts have not responded to the ARP refresh sent by 
N7k which in turn  trigger to delete  ARP entry  due to expiry. As a result   the route delete notification is 
sent to URIB from the process. However there is still traffic coming to given IP address as a result  the next packet that hit glean resulting in triggering ARP and  hope ARP is learnt from the host this time. 

Workaround(s):
Clear ip route <host>.

Related Community Discussions

Nexus 7010 intermittently dropping packets for certain SRC/DST IP
Hi, We have a pair of Nexus 7010 acting as the data centre gateways which connect to a pair of Nexus 5000 aggregators (using VPC) which then serves the end devices. N7K has separate VRFs for outside world by the name EXTERNAL and data centre by the name INNER (there are other VRFs but they are not relevant to this discussion). Inter-VRF routing is done by a firewall which implements data centre traffic policies (whats allowed, whats not). A traffic flow from a client to the server will look like ...
Latest activity: Feb 12, 2012
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