Route summarization with range from area 0 to a outside area

[hannes1967]

Dear friends,

I need to summarize routes from the backbone area to connected areas!

The line in the config of the ABR looks like:

router ospf 2

area 0 range 10.4.0.0 255.255.0.0

area 1 range 10.2.0.0 255.255.0.0

The routing table on a router in area 1 looks like this:

d7-2610xm-TelAnl#sh ip route os

     1.0.0.0/24 is subnetted, 1 subnets

O IA    1.0.0.0 [110/11] via 2.0.0.1, 00:18:31, FastEthernet0/0

     10.0.0.0/32 is subnetted, 2 subnets

O IA    10.4.1.1 [110/12] via 2.0.0.1, 00:18:31, FastEthernet0/0




No summary 10.4.0.0/16

Is summarization only supported from an area to backbone area?
I found some examples in the net from cisco training sites, which show that summary should als work from backbone area to outside!

regards, Hannes

[MHM Cisco World]

...

[Flavio Miranda]

Hi

 Summarization can be done on the ABR from area 0 to others areas. But, in your case, you have one network only, right? 

 The summarization would make sense if you were advertizing for example 

10.4.0.0/16

19.5.0.0/16

10.6.0.0/16

10.7.0.0/16

Then the aggragate route would be 10.4.0.0/14.

[hannes1967]

Hello and thanks!

I added two loopback interfaces in d4

11.4.1.1 255.255.0.0

11.5.1.1 255.255.0.0

Range config in d2:




d2(config-router)#do sh run | i ran

 area 0 range 11.0.0.0 255.0.0.0 not-advertise

 area 1 range 10.2.0.0 255.255.0.0




Routing table in d7:




d7#sh ip ro 11.0.0.0

Routing entry for 11.0.0.0/16, 2 known subnets




O IA    11.5.0.0 [110/3] via 2.0.0.1, 00:09:13, FastEthernet0/0

O IA    11.4.0.0 [110/3] via 2.0.0.1, 00:09:13, FastEthernet0/0

d7#

[MHM Cisco World]

...

[hannes1967]

d4 has lo 11.4.1.1 and l1 11.5.1.1 (both loopback in area

|

|    Area 0

|

d2 ABR

|

|     Area 1

|

d7 

[MHM Cisco World]

---

... 

[hannes1967]

The l0 and l1 are in area 8 at router d4

d4 ist connected to d2 in area 0

d2 ist connected to d7 in area 

d7 always has both networks separate in the routing table!

[MHM Cisco World]

...

[MHM Cisco World]

...

[hannes1967]

It works, when I use the

range

command in d4, but in the real network I don’t have responsibility on that ABR!

Thank you very much, I now have a better understanding!

[MHM Cisco World]

...

[MHM Cisco World]

...

[MHM Cisco World]

...

[David Ruess]

OSPF has limitations with a lot of things. Summary addresses being one of them. You can only summarize on the ABR or ASBR ....and even those commands are different from eachother.

If I  copied your network correctly I was able to summarize on D2 (ABR) into the rest of the area 2 on routes from Area.

-David