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Cisco Bug: CSCvt28368 - If routes connected to internal border are multiple AS hops away, full connectivity lost every 30s

Last Modified

Apr 02, 2020

Products (1)

  • Cisco DNA Center

Known Affected Releases

DNAC1.3.3.1

Description (partial)

Symptom:
Connectivity to resources accessed through internal border node will be accessible and inaccessible at 30 second intervals. This will continue to churn and never self-resolve.  

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debugging on the transit control plane node will show the routes to shared services through the internal border node will be added and removed (update churn) every 30 seconds.  

debug ip bgp vpnv4 unicast updates 192.168.10.7   <----this is the external border node at the site where the internal border node is importing routes.  

show ip bgp vpnv4 all summary  ---the table version will increase every 30 seconds.  
Example: this amount of churn was produced in about 12 hours

ISR-4451-07#show ip bgp vpnv4 all summary
BGP router identifier 192.168.10.7, local AS number 65001
BGP table version is 13151, main routing table version 13151 <-------
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On the external border node in the same fabric site as the internal border the best path route to prefixes to shared services (behind the internal border) will point to the transit control plane node.  Checking routes again, they will point to the local control plane node.  This will change every ~30 seconds.  

show ip route vrf CAMPUS 198.51.100.0

Conditions:
Distributed Campus (SDA  Transit)
Dedicated internal border node
Dedicated external border node
Dedicated Site-local control plane node

The connectivity issues will be present in the other fabric sites in the distributed campus. 
The churn will be present on the transit control plane node and the border nodes connected to SDA transit in the same site as the internal border node.
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