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Cisco Bug: CSCub10951 - BGP-DP: Missing updates for inter-cluster BE

Last Modified

Feb 11, 2018

Products (17)

  • Cisco IOS
  • Cisco 7301 Router
  • Cisco 7206 Router
  • Cisco ME 3600X-24TS-M Switch
  • Cisco 7206VXR Router
  • Cisco 7204 Router
  • Cisco 7202 Router
  • Cisco 7600 Series Route Switch Processor 720 with Multilayer Switch Feature Card
  • Cisco 7600 Series Route Switch Processor 720 with 10 Gigabit Ethernet Uplinks
  • Cisco ME 3600X-24FS-M Switch
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Known Affected Releases

15.2(4)S

Description (partial)

Symptoms: At RR, for an inter-cluster BE case, there are missing updates.

Conditions: This symptom is observed with the following conditions:

1) The following configuration exists at all RRs that are fully meshed:
- bgp additional-paths select best-external 
- nei x advertise best-external

2) For example, RR5 is the UUT. At UUT, there is,
- Overall best path via RR1.
- Best-external (best-internal) path via PE6 (client of RR5): for example,  the
path is called "ic_path_rr5".
- Initially, RR5 advertises "ic_path_rr5" to its nonclient iBGP peers, that is,
RR1 and RR3.

3) At PE6, unconfigure the route so that RR5 no longer has any inter-cluster BE
path. RR5 sends the withdrawals to RR1 and RR3 correctly.

4) At PE6, reconfigure the route so that RR5 will have "ic_path_rr5" as its   
"best-external (internal) path". At this point, even though the BGP table at
RR5 gets updated correctly, it does not send the updates to RR1 and RR3. They
never relearn the route.
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Bug Details Include

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