From: Brian Dennis (bdennis@internetworkexpert.com)
Date: Sat May 26 2007 - 15:40:27 ART
In regards to your question about using extended ACLs when filtering with
IGPs below is part of an email I sent previously on this subject (now part
of my personal wiki ;-).
Extended ACLs work with IGP protocols but you can not match on the subnet
mask portion of the route. Extended ACLs can be used with IGP protocols
to match the network portion of the route and the IP address of the
router (source) that sent the route. Here is an example of its usage:
Notice that R1 is receiving the 172.16.0.0/16 network from R2 (10.0.0.2)
and R3 (10.0.0.3). We will use ACL 100 and a distribute-list inbound so
that R1 only uses the 172.16.0.0/16 route that is being advertised by
R2.
Rack2R1#show ip route rip
R 172.16.0.0/16 [120/1] via 10.0.0.3, 00:00:06, Ethernet0/0
[120/1] via 10.0.0.2, 00:00:06, Ethernet0/0
R 192.168.0.0/24 [120/1] via 10.0.0.2, 00:00:06, Ethernet0/0
[120/1] via 10.0.0.3, 00:00:06, Ethernet0/0
Rack2R1#conf t
Enter configuration commands, one per line. End with CNTL/Z.
Rack2R1(config)#access-list 100 deny ip host 10.0.0.3 host 172.16.0.0
Rack2R1(config)#access-list 100 per ip any any
Rack2R1(config)#router rip
Rack2R1(config-router)#distribute-list 100 in e0/0
Rack2R1(config-router)#^Z
Rack2R1#
Rack2R1#clear ip route *
Rack2R1#show ip route rip
R 172.16.0.0/16 [120/1] via 10.0.0.2, 00:00:02, Ethernet0/0
R 192.168.0.0/24 [120/1] via 10.0.0.2, 00:00:02, Ethernet0/0
[120/1] via 10.0.0.3, 00:00:02, Ethernet0/0
Rack2R1#
More examples:
This would permit any 10.X.X.X/X network from 1.1.1.1 (i.e. 10.5.0.0/16,
10.1.1.4/30, 10.50.6.128/25, 10.1.1.64/26, etc)
access-list 100 permit ip host 1.1.1.1 10.0.0.0 0.255.255.255
This would permit any 10.1.X.X/X network from 1.1.1.1 (i.e. 10.1.1.0/24,
10.1.5.4/30, 10.1.50.128/25, 10.1.3.64/26, etc)
access-list 100 permit ip host 1.1.1.1 10.1.0.0 0.0.255.255
This would permit any 10.1.1.X/X network from 1.1.1.1 (i.e. 10.1.1.0/24,
10.1.1.0/30, 10.1.1.128/25, 10.1.1.64/26, etc)
access-list 100 permit ip host 1.1.1.1 10.1.1.0 0.0.0.255
You can also use the wild card mask on the host:
This would permit any 10.X.X.X/X network from 1.1.1.X (i.e. 10.5.0.0/16,
10.1.1.4/30, 10.50.6.128/25, 10.1.1.64/26, etc)
access-list 100 permit ip 1.1.1.0 0.0.0.255 10.0.0.0 0.255.255.255
HTH,
Brian Dennis, CCIE4 #2210 (R&S/ISP-Dial/Security/SP)
bdennis@internetworkexpert.com
Internetwork Expert, Inc.
http://www.InternetworkExpert.com
Toll Free: 877-224-8987
Direct: 775-745-6404 (Outside the US and Canada)
On 5/26/07 11:17 AM, "Raj Bansal" <ccie_study06@yahoo.com> wrote:
> Folks:
>
> Does rip have issues dealing with extended acls or expanded acls.?
>
> If I want to control a route, it seems that extended acls and expanded acls
> doesn't work. It seems to work with standard acls and prefix list. Reason I
> was trying to use an extended acl is to control the summary route being sent
> out with a /16.
>
> int serial0/0
> ip summary address rip 172.16.0.0 255.255.0.0
>
> router rip
> distribute list 10 out serial0/0 <---- works
> distribute list 101 out serial0/0 <----doesn't work
> distribute list prefix-list rip out serial0/0 <---works
> distribute list 2201 out serial0/0 <---doesn't work
>
> I can discount the expanded acls. Seems its used mostly in bgp sceanarios.
> But what's up with extended acl?
>
> One might argue why not use just the standard acl. But what if I have a
> route that is redistributed into rip and its a /32 (ospf point to multipoint
> with a /31). Now I match on the network and it gets leaked out to rip
> peer(neighbor).
>
> access-list 10 permit 172.16.0.0 0.0.0.0
> access-list 101 permit ip 172.16.0.0 0.0.0.0 255.255.0.0 0.0.0.0
> prefix-list rip permit 172.16.0.0/16.
>
> Thanks.
>
> Raj
>
>
>
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