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Cisco Bug: CSCus81948 - ISIS SR uses explicit null for InterArea prefixes

Last Modified

Jul 30, 2018

Products (1)

  • Cisco Carrier Routing System

Known Affected Releases

5.3.1.BASE

Description (partial)

Symptom:
In a Segment Routing environment, a ISIS router directly connected to an ISIS ABR router may incorrectly use Explicit Null label for the prefixes propagated or leaked by the ABR from another level.

While this doesn't break IP connectivity, it breaks end2end LSP and therefore breaks applications like L2 and L3 VPN which depend on the LSP.

Conditions:
The problem happens when the ISIS ABR sets the E flag in the Prefix SID sub-TLV for the prefixes propagated from other areas (as caused by CSCuq88112).
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