CCIE BGP PRACTICE LAB

[john.dejesus]

I am preparing for my ccie certification exam. and i am currently practicing bgp. I have a few questions regarding the bgp lab ( http://www.ibrahimhasan.com/content/lab-32-0 ). On task#4, is there any way that you could filter route advertisment outside of local AS without using prefix-lists or any type of filters?

Secondly, in http://ibrahim.drupalgardens.com/content/lab-31-0 task#3 is "network 150.1.1.0 mask 255.255.255.0 route-map SET-COMMUNITY" correct? or are there any way you could send a community string without using a route-map?

[Giuseppe Larosa · Accepted solution]

Hello John,

studying theory is needed to be able to understand the requirements

A)

>> Ensure that these prefixes are NEVER advertised out of AS 254

calls for BGP well known community NO-EXPORT to be set on these routes

B)

your understanding is correct the use of a route-map invoked in the network command looks like the only available option given the constraints

>> you are NOT allowed to use outbound or inbound route-maps when completing this task

Hope to help

Giuseppe

[john.dejesus]

Hi,

wait a moment. I think using NO-EXPORT would still advertise the prefix from AS 254. But this prefixes will not be propagated outside the ISP's AS. See example below.

AS 254 <-----> AS 1234 <-----> AS 456

Setting no export at AS 254. In this scenario, AS 1234 would still receive the prefix. but AS 1234 will not advertise it to AS 456. So I think no-export is not the solution to this problem.

any thoughts? :-)

the requirement is "NEVER advertised out of AS 254"

[Giuseppe Larosa · Accepted solution]

Hello John,

if you use the network 150.x.x.0 mask 255.255.255.0 route-map SET-COM on all routers in AS 254

where

route-map SET-COM permit 10

set community no-export

all the BGP prefixes are propagated within AS 254 in iBGP but not to future eBGP neighbors

Your note is valid when we set the BGP community on a route-map applied outbound to an eBGP neighbor. Here you are just required to modify the route-map of previous lab 31 invoked in BGP network command.

Hope to help

Giuseppe

[john.dejesus]

i see. it works. thanks for your help. :-)