From: Wang Dehong-DWANG1 (Dehong.Wang@motorola.com)
Date: Mon Oct 11 2004 - 20:18:26 GMT-3
Try to add the "le 32" to the line.. I think that 0.0.0.0/0 is the default route instead of any..
ip prefix-list ADV seq 5 deny 54.3.7.0/24
ip prefix-list ADV seq 10 deny 54.3.7.254/32
ip prefix-list ADV seq 15 permit 0.0.0.0/0
!
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of ccie2be
Sent: Monday, October 11, 2004 5:57 PM
To: Group Study
Subject: IE Lab 7 - Using deny in ip prefix lists
Hi guys,
I'm stump by this one.
R6 is connected to BB1 via subnet 54.3.7.0/24 and to R2 via 204.12.3.0/24.
R2 is config'd to only accept rip updates from R6. Here's R2's config:
router rip
version 2
network 204.12.3.0
distribute-list gateway R6 in
no auto-summary
!
ip prefix-list R6 seq 5 permit 204.12.3.6/32
And, here's the config for R6:
router rip
version 2
network 54.0.0.0
network 150.3.0.0
network 163.3.0.0
network 204.12.3.0
distribute-list prefix ADV out
distribute-list gateway R2 in
no auto-summary
!
ip prefix-list ADV seq 5 deny 54.3.7.0/24
ip prefix-list ADV seq 10 deny 54.3.7.254/32
ip prefix-list ADV seq 15 permit 0.0.0.0/0
!
ip prefix-list R2 seq 5 permit 204.12.3.2/32
I'm trying to get R2 to accept updates from which include subnet 150.3.0.0 and 163.3.0.0 but it seems that I can't achieve this by using the above prefix list ADV which denies the routes I don't want R2 to get.
However, everything works if instead of denying the routes I don't want R2 to get, I just explicitly permit the routes R2 should get.
In other words, the following prefix list works:
ip prefix-list ADV seq 5 permit 163.3.6.0/24
ip prefix-list ADV seq 10 permit 150.3.0.0/24
I don't understand this. Why is it OK to explicitly allow routes I want advertised and implicitly deny everything else but it's not OK to explicitly deny the routes I don't want and implicitly allow everything else?
It doesn't make sense. Can someone explain this? I'd be tremendously grateful.
Thanks, Tim
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