From: Mengdi Cao (xianglingzj@gmail.com)
Date: Tue Aug 22 2006 - 08:23:45 ART
Hi, Buddys,
I am quite confused when doing IEWB Lab 7 Q 5.3 Bestpath Selection.
It reads
" ... configure your network so that all traffic from AS100 destined for
prefixes ORIGINATED in AS 54 transits the link to BB1."
" ... configure your network so that all traffic from AS100 destined for
prefixes that are FROM CUSTOMERS of AS 54 is sent out towards BB3"
From my understanding, "prefixes originated in AS54" should be directly from
AS 54 (by network statment or redistribution), thus the AS_PATH should be a
single "54" when entering AS100. Those willl some other things ahead of 54
should be orginiated from other AS, i.e., "prefixes from customers of AS
54". Thus I designed the answer as:
!
router bgp 100
bgp default local 100
nei 54.1.7.254 route-m BB1 in
nei 204.12.1.254 route-m BB3 in
!
ip as-pa access-l 1 per ^54$
!
route-m BB1 per 1
m as- 1
s local- 200
!
route-m BB1 per 10
!
route-m BB3 per 10
m as-path 1
s local- 50
!
route-map BB3 per 20
!
But when I checked it up with the answer I found the answer is roughly the
same but it's AS_PATH access list uses _54$ instead of ^54$. From my
understanding that _54$ matches anything ends with 54. And in this answer
it is the same as match anything as this is applying on the EBGP neighbour
of AS 54. Thus I can not agree with this answer. Anyone got comments on
it?
This archive was generated by hypermail 2.1.4 : Fri Sep 01 2006 - 15:41:58 ART