OSPF External Route - Choosing one ASBR

From: gladston@br.ibm.com
Date: Mon May 16 2005 - 09:46:30 GMT-3


R1 and R5 injects de same route, 55.55.55.0, on area 0
Metric used on redistribution is the same, 20.
Metric to ASBR R1 and R5, from CAT2, is the same, 65.

CAT2 always choose R5. Are you aware of the reason?
Rack2CAT2#sir 55.55.55.0
Routing entry for 55.55.55.0/24
  Known via "ospf 1", distance 110, metric 20, type extern 2, forward metric 65
  Last update from 142.20.28.2 on Vlan20, 00:00:27 ago
  Routing Descriptor Blocks:
  * 142.20.28.2, from 142.20.5.1, 00:00:27 ago, via Vlan20
      Route metric is 20, traffic share count is 1

Rack2CAT2#
Rack2CAT2#sh ip os da ex
Rack2CAT2#sh ip os da external 55.55.55.0

       OSPF Router with ID (142.20.8.1) (Process ID 1)

                Type-5 AS External Link States

  Routing Bit Set on this LSA
  LS age: 838
  Options: (No TOS-capability, DC)
  LS Type: AS External Link
  Link State ID: 55.55.55.0 (External Network Number )
  Advertising Router: 142.20.1.1
  LS Seq Number: 80000001
  Checksum: 0x73E2
  Length: 36
  Network Mask: /24
        Metric Type: 2 (Larger than any link state path)
        TOS: 0
        Metric: 20
        Forward Address: 0.0.0.0
        External Route Tag: 0

  Routing Bit Set on this LSA
  LS age: 43
  Options: (No TOS-capability, DC)
  LS Type: AS External Link
  Link State ID: 55.55.55.0 (External Network Number )
  Advertising Router: 142.20.5.1
  LS Seq Number: 80000001
  Checksum: 0x57FA
  Length: 36
  Network Mask: /24
        Metric Type: 2 (Larger than any link state path)
        TOS: 0
        Metric: 20
        Forward Address: 0.0.0.0
        External Route Tag: 0

Rack2CAT2#
Rack2CAT2#
Rack2CAT2#sir 55.55.55.0
Routing entry for 55.55.55.0/24
  Known via "ospf 1", distance 110, metric 20, type extern 2, forward metric 65
  Last update from 142.20.28.2 on Vlan20, 00:02:17 ago
  Routing Descriptor Blocks:
  * 142.20.28.2, from 142.20.5.1, 00:02:17 ago, via Vlan20
      Route metric is 20, traffic share count is 1

Rack2CAT2#
Rack2CAT2#sh ip os da external 55.55.55.0

       OSPF Router with ID (142.20.8.1) (Process ID 1)

                Type-5 AS External Link States

  Routing Bit Set on this LSA
  LS age: 940
  Options: (No TOS-capability, DC)
  LS Type: AS External Link
  Link State ID: 55.55.55.0 (External Network Number )
  Advertising Router: 142.20.1.1
  LS Seq Number: 80000001
  Checksum: 0x73E2
  Length: 36
  Network Mask: /24
        Metric Type: 2 (Larger than any link state path)
        TOS: 0
        Metric: 20
        Forward Address: 0.0.0.0
        External Route Tag: 0

  Routing Bit Set on this LSA
  LS age: 144
  Options: (No TOS-capability, DC)
  LS Type: AS External Link
  Link State ID: 55.55.55.0 (External Network Number )
  Advertising Router: 142.20.5.1
  LS Seq Number: 80000001
  Checksum: 0x57FA
  Length: 36
  Network Mask: /24
        Metric Type: 2 (Larger than any link state path)
        TOS: 0
        Metric: 20
        Forward Address: 0.0.0.0
        External Route Tag: 0

Rack2CAT2#
Rack2CAT2#sh ip os border-routers

OSPF Process 1 internal Routing Table

Codes: i - Intra-area route, I - Inter-area route

i 142.20.2.1 [1] via 142.20.28.2, Vlan20, ABR/ASBR, Area 16, SPF 2
I 142.20.4.1 [1065] via 142.20.28.2, Vlan20, ASBR, Area 16, SPF 2
I 142.20.5.1 [65] via 142.20.28.2, Vlan20, ASBR, Area 16, SPF 2
I 142.20.1.1 [65] via 142.20.28.2, Vlan20, ASBR, Area 16, SPF 2
Rack2CAT2#
Rack2CAT2#sir 142.20.1.1
Routing entry for 142.20.1.1/32
  Known via "ospf 1", distance 110, metric 66, type inter area
  Last update from 142.20.28.2 on Vlan20, 00:22:19 ago
  Routing Descriptor Blocks:
  * 142.20.28.2, from 142.20.2.1, 00:22:19 ago, via Vlan20
      Route metric is 66, traffic share count is 1

Rack2CAT2#sir 142.20.5.1
Routing entry for 142.20.5.1/32
  Known via "ospf 1", distance 110, metric 66, type inter area
  Last update from 142.20.28.2 on Vlan20, 00:22:23 ago
  Routing Descriptor Blocks:
  * 142.20.28.2, from 142.20.2.1, 00:22:23 ago, via Vlan20
      Route metric is 66, traffic share count is 1

Rack2CAT2#



This archive was generated by hypermail 2.1.4 : Fri Jun 03 2005 - 10:11:58 GMT-3