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Cisco Bug: CSCuq44349 - Traffic from 6800IA may hit 0x7FA9 & get dropped on VSS

Last Modified

Dec 18, 2019

Products (1)

  • Cisco Catalyst 6000 Series Switches

Known Affected Releases

15.1(2)SY3 15.2(1a)SY2.1

Description (partial)

Symptom:
Certain UDP packets arriving only on the VSS standby switch via the RSL MEC may hit 0x7FA9 on VSS standby and get blackholed. ELAM on VSS standby shows these values for packet on non working case:

DEST_INDEX ...................... [19] = 0x7FA9 [Switch/Router]
DISABLE_NL ...................... [1] = 1
DISABLE_IL ...................... [1] = 1

  For example, certain Access point connected on FEX try to get an IP from BOOTP Server through BOOTP (UDP broadcast) which is connected beyond the VSS and do not get an IP.   ELAM reveals that the bootp request made it to VSS standby only and got dropped after hitting the security rate limiter.

Other UDP based services may also be affected.

Conditions:
Traffic coming from 6800IA and hitting VSS to get forwarded upstream.
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