OSPF: could not Summarize

[noeljr311]

Hi Guys,

I wasn't able to summarize these:

192.168.1.0/25 is subnetted, 2 subnets

O 192.168.1.0/25 [110/2] via 192.168.3.130, 00:03:58, GigabitEthernet0/0

O 192.168.1.128/25 [110/2] via 192.168.3.130, 00:03:30, GigabitEthernet0/0

192.168.2.0/25 is subnetted, 2 subnets

O 192.168.2.0/25 [110/2] via 192.168.3.130, 00:03:45, GigabitEthernet0/0

O 192.168.2.128/25 [110/2] via 192.168.3.130, 00:03:30, GigabitEthernet0/0

This are my commands:

Switch(config-router)#area 0 range 192.168.1.0 255.255.255.128

Switch(config-router)#area 0 range 192.168.2.0 255.255.255.128

[Martin L]

192.168.1.0/25 is equal to 192.168.1.0 255.255.255.128 so there is nothing to summarize , right?

255.255.255.128 is /25

try area 0 range 192.168.1.0 255.255.255.0  <<aka /24 it should show up as summarized now

Regards, ML
**Please Rate All Helpful Responses **

[Giuseppe Larosa]

Hello @noeljr311 ,

@Martin L is correct in his answer to be able to summarize at area border on ABR, you need to use a /24 prefix length that is equivalent to a wild card mask of 255.255.255.0

In addition to this you need to have an OSPF multiarea to see it working: the effects of the command are visible in the OSPF database of all other areas different from area 0.

This is the true meaning of the command: the ABR in creating the LSA type 3 inter-area routes called unfortunately summary LSA will take in account the area range commands and will create summarized LSA type 3 that will be sent in areas different from the source area (the area where the route components exist as part of a LSA type 1 or as a LSA type 2).

Hope to help

Giuseppe