As Path Filtering

[Cisco-Spider]

Hello,

I am receiving a BGP global routing table. I want to filter all of them and only allow with the following AS Numbers.

example:

1234 1111

1234 2222

1234 3333

1234 4444

1234 5555

1234 6666

Please help me.

[lgijssel]

You may find the following link useful:

http://www.cisco.com/en/US/tech/tk365/technologies_tech_note09186a0080094a92.shtml

regards,

Leo

[Cisco-Spider]

not much information.

[lgijssel]

Yeah, reading is difficult or would you perhaps like us to write it out for you?

Your issue seems to be about filtering prefixes with a certain path list which is described in the link as follows:

Only Allow Networks That Have Passed Through AS 4 to Enter AS 3
If you want only the networks that have passed through AS 4 to enter AS 3 from Router 3, you can apply an inbound filter on Router 3.

ip as-path access-list 1 permit _4_

router bgp 3
neighbor 2.2.2.2 remote-as 1
neighbor 2.2.2.2 route-map foo in

route-map foo permit 10
match as-path 1

[Marwan ALshawi]

your question not very specific !

- do you want the AS path to be match based on the existence of the above AS numbers in the path

for example any AS path has 1234 1111 in it

- or do you want to the AS path to be exact match

for example only route with AS path 1234 1111

for case 1 you can use AS path like _1234_1111_

for case 2 you can use AS path like  ^1234_1111$

hope this help

if helpful Rate

[JohnTylerPearce · Accepted solution]

1234 1111

1234 2222

1234 3333

1234 4444

1234 5555

1234 6666

Sounds like you want to accept only the AS Paths of 1234 and or [1111,2222,3333,4444,5555,6666]

R1---->ISP1

ip as-path 1 permit ^1234_1111$

ip as-path 1 permit ^1234_2222$

ip as-path 1 permit ^1234_3333$

ip as-path 1 permit ^1234_4444$

ip as-path 1 permit ^1234_5555$

ip as-path 1 permit ^1234_6666$

router bgp 1

neighbor x.x.x.x remote-as x

neighbor x.x.x.x route-map FILTERME in

route-map FILTERME permit 10

match as-path 1

[Cisco-Spider]

Thank you very much. This is what i am looking for.

[Marwan ALshawi · Accepted solution]

which is described in case 2 in my post above !

[lgijssel]

And even in my post, scenario 4

Only Allow Networks Originated from AS 4, and ASs Directly Attached to AS 4, to Enter Router 1

Thnx4notrating

Leo