OSPF summary address democratic?

From: Gustavo Novais (gustavo.novais@novabase.pt)
Date: Sat Nov 19 2005 - 14:25:46 GMT-3


Hello

Doing some tests with how routes are summarized on OSPF

I have 4 external routes that I wish to aggregate. I redistribute into
OSPF, changing their metric-type (some are E1, some are E2)

When I do summary address, which will be the route-type of this
aggregate?

I was not able to reach a definitive answer to this, because when I
marked 2 routes E1 and two routes E2, the summary was a E1, and if I did
1 route E1 and three routes E2, the summary will be E2?

I will post my tests (I'm doing load balancing, but nevermind that):

2 routes E1 and 2 routes E2 - Before summary address

Sh ip route:

     30.0.0.0/16 is subnetted, 4 subnets

O E1 30.2.0.0 [110/84] via 141.1.54.4, 00:00:10, Serial0/0

                 [110/84] via 141.1.145.4, 00:00:10, FastEthernet0/0

O E2 30.3.0.0 [110/20] via 141.1.54.4, 00:00:10, Serial0/0

                 [110/20] via 141.1.145.4, 00:00:10, FastEthernet0/0

O E1 30.0.0.0 [110/84] via 141.1.54.4, 00:00:06, Serial0/0

                 [110/84] via 141.1.145.4, 00:00:06, FastEthernet0/0

O E2 30.1.0.0 [110/20] via 141.1.54.4, 00:00:11, Serial0/0

                 [110/20] via 141.1.145.4, 00:00:11, FastEthernet0/0

After summary address:

O E1 30.0.0.0 [110/84] via 141.1.54.4, 00:00:07, Serial0/0

                 [110/84] via 141.1.145.4, 00:00:07, FastEthernet0/0

1 Route E1 and 3 routes E2 - Before summary address

Sh ip route:

     30.0.0.0/16 is subnetted, 4 subnets

O E2 30.2.0.0 [110/20] via 141.1.54.4, 00:00:14, Serial0/0

                 [110/20] via 141.1.145.4, 00:00:14, FastEthernet0/0

O E2 30.3.0.0 [110/20] via 141.1.54.4, 00:00:14, Serial0/0

                 [110/20] via 141.1.145.4, 00:00:14, FastEthernet0/0

O E1 30.0.0.0 [110/84] via 141.1.54.4, 00:00:26, Serial0/0

                 [110/84] via 141.1.145.4, 00:00:26, FastEthernet0/0

O E2 30.1.0.0 [110/20] via 141.1.54.4, 00:00:14, Serial0/0

                 [110/20] via 141.1.145.4, 00:00:14, FastEthernet0/0

After summary address:

     30.0.0.0/14 is subnetted, 1 subnets

O E2 30.0.0.0 [110/20] via 141.1.54.4, 00:00:20, Serial0/0

                 [110/20] via 141.1.145.4, 00:00:20, FastEthernet0/0

I was expecting that some kind of preference was given to E1 routes, but
apparently only when untying the number of routes.

Can anybody shed some light/document on this?



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