I have a Route-Map question that I'm very confused about:
The scenario is from Caslow (p840), it is as follows:
Company A has a full T3 connection to the Internet thru the ISP AAA-101.NET.
Company B has a T1 connection to the Internet thru the ISP BBB-202.Net.
Company A acquires Company B, but Company A wants to keep both Internet
connections, with the exception of packets originating from the AS of
BBB-202.Net (BBB-202.Net's AS is 202). All traffic originating from AS 202
will use the T1 Internet connection.
Caslow states in order to do this, the following configs should be used on
RouterB
router bgp 1000
neighbor 10.1.1.1 remote-as 1000
neighbor 172.16.1.100 remote-as 202
neighbor 172.16.1.100 route-map AS-200-IN in
no ip classless
ip as-path access-list 1 permit _300$
route-map AS-200-IN permit 10
match as-path 1
set local-preference 200
route-map AS-200-IN permit 20
What I don't understand is:
With the "set local-preference 200" statement, it directs the traffic
(routes coming from AS 202 / neighbor 172.16.1.100) to go out via Router B.
However, what makes the router not passing any other routes (not from AS
200)? Wouldn't they still be able to go out thru Router B as well? In
consideration that the local preference has not been changed on the router.
Any help will be greatly appreciated.
Best Regards,
Hunt Lee
System Engineer
WebCentral
Message Posted at:
http://www.groupstudy.com/form/read.php?f=7&i=34431&t=34431
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