Viewing the World in Binary

OSPF/BGP – A few good things…

OSPF NOTES:

  • If router-id command not used under ‘ospf router’ definition

-> RI will be highest IP addr of a loopback interface. No loopback defined,  Then..

->  RI will be highest IP addr of first active interface.

  • Enabling OSPF on all interfaces

-> network 0.0.0.0 255.255.255.255 area <number>

BGP NOTES:

  • ebg-multihop option can only be used for eBGP and is not used for iBGP.
  • If ‘sh ip bgp summary’ shows state transitioning between Idle <-> Active. This is an indication of TCP issues between Peers.

BGP Load Balancing

  • Load Balancing in BGP – If the AS Path is different for route to same network, only one path will be installed in the routing table.  Load balancing will not take place.

EDGE1#sh ip route 30.30.30.0
Routing entry for 30.30.30.0/24
  Known via “bgp 60055”, distance 20, metric 0
  Tag 10055, type external
  Redistributing via ospf 1
  Last update from 200.200.200.1 00:37:40 ago
  Routing Descriptor Blocks:
  * 200.200.200.1, from 200.200.200.1, 00:37:40 ago
      Route metric is 0, traffic share count is 1
      AS Hops 2
      Route tag 10055

EDGE1#sh ip bgp 30.30.30.0
BGP routing table entry for 30.30.30.0/24, version 30
Paths: (2 available, best #2, table Default-IP-Routing-Table)
  Advertised to update-groups:
     1
  20055 3000
    200.200.200.3 from 200.200.200.3 (200.200.200.10)
      Origin IGP, localpref 100, valid, external
  10055 3000
    200.200.200.1 from 200.200.200.1 (200.200.200.2)
      Origin IGP, localpref 100, valid, external, best

EDGE1#sh ip bgp

—- Output snipped —–

*  30.30.30.0/24    200.200.200.3                          0 20055 3000 i   <- Two different paths are present for route to network 30.30.30.0
*>                  200.200.200.1                          0 10055 3000 i

———————-

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September 11, 2008 - Posted by | Protocols - OSPF |

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