Technical Note: How to filter incoming OSPF routes using access-list on IP address

[kbahrudin_FTNT]

Description

This article provides an example showing how to filter the incoming OSPF routes using access-list on IP address.

Scope

OSPF route filtering.

Solution

config router ospf
set abr-type cisco -> set type as ABR
config distribute-list
edit 1
set access-list "TEST" -> apply access-list
next
end
end

config router access-list
edit "TEST"
config rule
edit 1
set action deny -> set action deny to reject the route
set prefix X.X.X.X N.N.N.N -> set the route to filter
set exact-match enable -> to match exact route
next
end
next
end

This example assumes the route to filter is 10.206.55.0/24.

Before Filter

# get router info ospf database brief

Summary Link States (Area 0.0.0.0)
Link ID         ADV Router      Age  Seq#     CkSum Flag Route
10.206.55.0     10.205.240.59   790  8000013c 5426  0012 10.206.55.0/24
10.206.59.0     10.205.240.59   933  8000013c 284e  0012 10.206.59.0/24

After Filter

# get router info ospf database brief

Summary Link States (Area 0.0.0.0)
Link ID         ADV Router      Age  Seq#     CkSum Flag Route
10.206.59.0     10.205.240.59   933  8000013c 284e  0012 10.206.59.0/24