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Cisco Bug: CSCvr92638 - OSPF External Type-1 Route Present in OSPF Database but not in RIB

Last Modified

Aug 25, 2020

Products (1)

  • Cisco IOS

Known Affected Releases

Gibraltar-16.12.1b

Description (partial)

Symptom:
-Under certain circumstances, an OSPF External Type-1 route will be present in the OSPF database but will not be installed in the RIB despite being the best route available
-This seems to be dependent on the E1 route being removed and readded to the OSPF database while an E2 route is also present in the DB
-Example output showing this

Conditions:
CAT9K_OSPF#show ip ospf database external 1.1.1.1

            OSPF Router with ID (30.30.30.30) (Process ID 0)

                Type-5 AS External Link States

  LS age: 704
  Options: (No TOS-capability, DC, Upward)
  LS Type: AS External Link
  Link State ID: 1.1.1.1 (External Network Number )
  Advertising Router: 10.10.10.10
  LS Seq Number: 80000005
  Checksum: 0x98BF
  Length: 36
  Network Mask: /32
        Metric Type: 2 (Larger than any link state path)
        MTID: 0 
        Metric: 20 
        Forward Address: 0.0.0.0
        External Route Tag: 0

  LS age: 22
  Options: (No TOS-capability, DC, Upward)
  LS Type: AS External Link
  Link State ID: 1.1.1.1 (External Network Number )
  Advertising Router: 20.20.20.20
  LS Seq Number: 80000001
  Checksum: 0x1660
  Length: 36
  Network Mask: /32
        Metric Type: 1 (Comparable directly to link state metric)
        MTID: 0 
        Metric: 20 
        Forward Address: 0.0.0.0
        External Route Tag: 0

CAT9K_OSPF#show ip route 1.1.1.1
% Network not in table

Conditions:
-Any box running affected version of code
-OSPF configuration in which E1 and E2 paths are learned for the same prefix
-E1 metric (forwarding dist to ASBR + external metric) > E2 metric (external metric)
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