BugZero | Cisco BugID CSCvi83758 - BGP doesn't reclaim per-vrf label if all prefixes ...

Cisco - Defect ID: CSCvi83758

BGP doesn't reclaim per-vrf label if all prefixes are withdrawn between lsd down and up event.

Cisco - Defect ID: CSCvi83758

BGP doesn't reclaim per-vrf label if all prefixes are withdrawn between lsd down and up event.

Last updated on January 7th, 2025

BugZero Risk Score
7.8 High

Overall: 7.8

Severity: 8.2

Lifecycle: 9.1

Popularity: 4.6

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Bug Details

Views: 2

Description

Symptom

Label collision for the per-vrf label can be seen if lsd connection with bgp flaps. It will cause traffic drop for prefixes in that vrf.

Conditions

Issue will happen if following events happen in chronological order: 1) In steady state bgp has allocated label L1 for vrf VRF1 with per-vrf label mode on. 2) LSD connection goes down. 3) All prefixes in the vrf VRF1 gets withdrawn. 4) LSD connection comes up. 5) BGP doesn't now reclaim label L1 from lsd. (At this point lsd thinks label L1 is free for use.) 6) Prefix gets learned in VRF1. BGP thinks label L1 is active and starts using it. 7) LSD assigns label L1 to someone else. Lets's say some other vrf in bgp. This causes label collision.

Workaround

LSD connection with BGP shouldn't flap often. If there is situation when connection is flapping then make sure there is at least one prefix in vrf to prevent this issue.

Further Problem Description

This is applicable to all platforms and all previous releases.

Change history

2025-01-07 Added: 6.3.3, 6.4.2, 6.4.3, 6.5.1, 6.5.15, 6.5.2, 6.5.25, 6.5.26, 6.5.28, 6.5.29, 6.5.3, 6.5.92, 6.5.93, 6.6.1, 6.6.11, 6.6.12, 6.6.2, 6.6.25, 6.6.3, 6.6.4, 6.7.1, 6.7.2, 6.7.3, 6.7.4, 7.0.0, 7.0.1, 7.0.11, 7.0.12, 7.0.14, 7.0.2, 7.0.90, 7.1.1, 7.1.15, 7.1.2, 7.1.25, 7.1.3, 7.2.0, 7.2.1, 7.2.12, 7.2.2, 7.3.0, 7.3.1

Links

Original Vendor Announcement

Relevant Products

Click on a version to see all relevant bugs

Affected versions:No known affected versions

Fixed versions: 6.3.3, 6.4.2, 6.4.3, 6.5.1, 6.5.15, 6.5.2, 6.5.25, 6.5.26, 6.5.28, 6.5.29, 6.5.3, 6.5.92, 6.5.93, 6.6.1, 6.6.11, 6.6.12, 6.6.2, 6.6.25, 6.6.3, 6.6.4, 6.7.1, 6.7.2, 6.7.3, 6.7.4, 7.0.0, 7.0.1, 7.0.11, 7.0.12, 7.0.14, 7.0.2, 7.0.90, 7.1.1, 7.1.15, 7.1.2, 7.1.25, 7.1.3, 7.2.0, 7.2.1, 7.2.12, 7.2.2, 7.3.0, 7.3.1

Relevant Products

Click on a version to see all relevant bugs

Affected versions:No known affected versions

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Cisco - Defect ID: CSCvi83758

BGP doesn't reclaim per-vrf label if all prefixes are withdrawn between lsd down and up event.

Cisco - Defect ID: CSCvi83758

BGP doesn't reclaim per-vrf label if all prefixes are withdrawn between lsd down and up event.

Last updated on January 7th, 2025

BugZero Risk Score7.8 High

Bug Details

Symptom

Conditions

Workaround

Further Problem Description

Links

Top Cisco Defects

Ready to prevent the next vendor outage?

BugZero Risk Score
7.8 High