From: Michael Snyder (msnyder@revolutioncomputer.com)
Date: Fri Feb 13 2004 - 02:50:51 GMT-3
Perhaps we can also use the distance command for similiar occurrances in
other routing protocols -> to deny our networks from coming back to us
from the other routers.
----------------------------------------------
Hi Ron,
I use one way tags for that purpose.
I tag going into my core network, and block the same tag from coming
back out of the core to the peripheral network. Note I said the same
tag. I let other tags pass thru the core into the peripheral networks.
(rip)----(core ospf or eigrp)----(isis)
In this case I tag rip going into the core with one tag; and block that
tag from the core back to rip.
Same with isis. But the rip tagged routes can transit into isis and
vice versa. Neat trick is rip version one and isis doesn't support
tags. Using this technique it doesn't affect the outcome. The logic is
applied before getting to rip or isis, etc.
If you have multiple routers that touch multiple parts of the igp`s, I
use the same tags at each point. In fact I cut and paste the same
commands per distribution point of the same igp`s, to keep everything
consistent.
Here's a simple example.
router ospf 35
router-id 210.2.2.2
log-adjacency-changes
redistribute rip metric 1000 metric-type 1 subnets tag 444
network 172.31.12.0 0.0.0.255 area 2
network 172.31.56.0 0.0.0.7 area 0
neighbor 172.31.56.6
neighbor 172.31.56.5
!
router rip
version 2
redistribute ospf 35 metric 3 match internal external 1 external 2
route-map catch444
passive-interface default
no passive-interface Serial0.24
network 172.31.0.0
no auto-summary
!
route-map catch444 deny 5
match tag 444
!
route-map catch444 permit 10
!
Type-5 AS External Link States
Link ID ADV Router Age Seq# Checksum Tag
172.31.24.0 210.2.2.2 140 0x8000002C 0xF8AA 444
172.31.40.0 210.2.2.2 628 0x8000002C 0x484B 444
172.31.69.0 210.6.6.6 691 0x8000002D 0xDC5F 999
172.31.78.0 210.7.7.7 1653 0x8000002D 0x5EBF 777
172.31.80.0 210.7.7.7 1653 0x8000002F 0x9E6C 777
210.1.1.1 210.1.1.1 342 0x8000005A 0xC87B 0
210.2.2.2 210.2.2.2 1638 0x80000059 0x94AA 0
210.4.4.0 210.2.2.2 628 0x8000002C 0x2B81 444
210.5.5.5 210.5.5.5 1046 0x80000059 0xF13B 0
210.6.6.6 210.6.6.6 692 0x8000002D 0x143F 0
210.7.7.7 210.7.7.7 1654 0x8000005C 0x7F9E 0
210.8.8.8 210.7.7.7 1654 0x8000002F 0x8EAD 777
210.9.9.9 210.6.6.6 692 0x80000031 0x2A31 999
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