ospf Summarize routes

[feroz syed]

Hi,

its ospf network, i'm facing some problem when i try to summarize routes between from area0 to area 1, Router5 placed in area0 its has couple of loop address and router 2 (ABR) want to summarize those address in to area 1.

here is the error message when i try to advertise this routes

R2(config-router)#area 1 range 172.12.1.0 255.255.240.0

% OSPF: Inconsistent address/mask 172.12.1.0/20 for area range

   172.12.0.0/24 is subnetted, 6 subnets

O       172.12.1.0 [110/65] via 10.1.246.5, 00:06:45, Serial1/0

O       172.12.4.0 [110/65] via 10.1.246.5, 00:06:45, Serial1/0

O       172.12.5.0 [110/65] via 10.1.246.5, 00:06:45, Serial1/0

O       172.12.6.0 [110/65] via 10.1.246.5, 00:06:45, Serial1/0

O       172.12.8.0 [110/65] via 10.1.246.5, 00:06:45, Serial1/0

O       172.12.10.0 [110/65] via 10.1.246.5, 00:06:45, Serial1/0

[Rolf Fischer · Accepted solution]

Hi,

you have to summarize those networks in Area 0.

area range command:

area-id: Identifier of the area about which routes are to be summarized. It can be specified as either a decimal value or as an IPv6 prefix.

HTH

Rolf

[feroz syed]

Hi,

Router 5 already placed in Area0, can we summarize routes inside the area ?

[Jon Marshall · Accepted solution]

You cannot summarise routes in OSPF within the same area. You can summarise -

1) on the ASBR when you inject routes into your OSPF domain

and

2) when you pass routes from one area to another area.

Jon

[Rolf Fischer]

You need to use the area range command on the ABR to summarize to other areas:

R2(config-router)#area 0 range 172.12.1.0 255.255.240.0

Inside an area you can't summarize or filter, because the LSDBs of all routers within an area have to be the same. This is, among scalability and limiting the scope of the SPF algorithm, one of the main concepts of link-state routing protocols hierarchy.

[feroz syed]

if you see the diagram, router 2 is ABR for area 1 its connected to area 0 and area 1,

R2(config-router)#area 1 range 172.12.1.0 255.255.240.0

But i mention wrong area id just saw the fischer post.

if its work i ll close this post .

[feroz syed]

But stil the same error showing even i change the area id from1 to 0

R2(config-router)#area 0 range 172.12.1.0 255.255.240.0

% OSPF: Inconsistent address/mask 172.12.1.0/20 for area range

[Jon Marshall · Accepted solution]

Instead of 172.12.1.0 255.255.240 try 172.12.0.0 255.255.240.0.

Jon

[feroz syed]

Thanks for the correction working