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Filtering in OSPF routes without "area" command?

linus-ardstal
Level 1
Level 1

Hi! Is there a way to filter OSPF routes without the "Area" command?
I could swear I've done it before, but I can't seem to replicate it again.

I am in CML, and my topology is R1--R2--R3.

Link between R1 to R2 is area 0, R2 to R3 area 1.

From what I recall from my previous attempts, I used a distribute-list to filter routes from R1 to R3 by placing it on the ABR, R2. Now, I have tried using a prefix-list in my distribute-list both in and out of R2. In of course removes it from R2's routing table, but I do have a memory of it removing the route from R3 aswell?

Answers appreciated. Thanks!

10 Replies 10

area <X> filter-list prefix <> IN/OUT

this command can use instead of area range

MHM

That is using the Area command though.

area BUT not area range 

MHM

That is not what I asked for, but thanks anyways.

In of course removes it from R2's routing table, but I do have a memory of it removing the route from R3 aswell?
you can not use distribute-list to remove prefix from DB of OSPF so you have only two option 
1- area range 

2- area filter-list 

Route Filtering Using the distribute-list Command > CCNP Routing and Switching Portable Command Guide: Configuration of Redistribution | Cisco Press

Screenshot (532).png

that all I have 

goodluck 

MHM

Alright. Thanks for the help, maybe I mixed it up.

linus-ardstal
Level 1
Level 1

Managed to make it work again. I added another router:

R1--R2--R3--R4.

I made a prefix-list on R3 denying the link between R1 to R2 from being advertised to R4. On R3: "Distribute-list prefix prefix in", R3 being ABR between area 0 and area 1, this prevented the route from being learned on R4.

One prefix or ALL prefix will effect by this list?
add LO in R1 and see if R4 see it or not 

I think you make all R1/R2 hidden from R4 not only one prefix 

MHM

The link between R1-R2 is removed, but R1's loopback is still visible on R4.

"Ip prefix-list NOR1 deny 12.12.12.0/29"

"Ip prefix-list NOR1 permit 0.0.0.0/0 le 32"

"Distribute-list prefix NOR1 in" on R3

The route to 10.10.10.1 (R1's lo0) is still visible on R4.

In R4 and R3 can I see show ip route