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Cisco Bug: CSCui93977 - FIB entry is not deleted due to version mismatch (rework of CSCuc95925)

Last Modified

Aug 31, 2020

Products (20)

  • Cisco ASR 9000 Series Aggregation Services Routers
  • Cisco CRS-1 Line Card Chassis (Dual)
  • Cisco CRS-1 16-Slot Line Card Chassis
  • Cisco CRS-3 Multishelf System
  • Cisco CRS-1 Line Card Chassis (Multi)
  • Cisco IOS XR Software
  • Cisco ASR 9922 Router
  • Cisco CRS-1 4-Slot Single-Shelf System
  • Cisco ASR 9010 Router
  • Cisco CRS-3 8-Slot Single-Shelf System
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Known Affected Releases

4.3.2.BASE 4.3.3.FWDG

Description (partial)

Symptom:
FIB stops processing route modify or delete on one or all line cards.

* Identify the CEF tables to check

RP/0/RSP1/CPU0:ASR9000# show cef tables 

(removed)

Table           Table ID             L          R           T C D M S
default         0xe0000000          497          483448          42 Y N N Y
INSIDE          0xe0000010           0          0           5 Y N N Y
OUTSIDE         0xe0000011           0          0           5 Y N N Y

(removed)

* Check the default table

RP/0/RSP0/CPU0:ASR9000# show cef ipv4 summary | include CEF
IP CEF with switching (Table Version 0) for node0_RSP0_CPU0
  0 CEF route update drops, 1484155400 revisions of existing leaves
  4871099 CEF route update drops due to version mis-match 

* Check the VRF tables

RP/0/RSP1/CPU0:ASR9000# show cef vrf INSIDE summary | include CEF
IP CEF with switching (Table Version 0) for node0_RSP1_CPU0
  0 CEF route update drops, 0 revisions of existing leaves
  0 CEF route update drops due to version mis-match

RP/0/RSP1/CPU0:ASR9000# show cef vrf OUTSIDE summary | include CEF
IP CEF with switching (Table Version 0) for node0_RSP1_CPU0
  0 CEF route update drops, 0 revisions of existing leaves
  0 CEF route update drops due to version mis-match

Conditions:
This problem can happen mostly in some continuous route-churn scenario, which causes a lot of route updates to FIB (more than 2 billion) and hence reach limit of a 32-bit version number.

Under normal conditions, for a router with reasonable route churn, this condition should never be hit. For instance - at 100K route updates/per table/per day, it will take 58+ years to reach 2 Billion route updates.

Additionally this issue can be the result of an unsuccessful switchover:

sh cef summary
<snip>
295 CEF route update drops due to version mis-match <<<<< Increasing counter

In conjunction with multiple logs of route update skipped:

RP: version mismatch: Route-Update skipped for Prefix=X.X.X.X/30, rte-ver=2839120, leaf-ver=2839121
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Bug Details Include

  • Full Description (including symptoms, conditions and workarounds)
  • Status
  • Severity
  • Known Fixed Releases
  • Related Community Discussions
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