From: Godswill Oletu (oletu@inbox.lv)
Date: Sun Jul 02 2006 - 20:45:48 ART
Sami,
They both will achieve the same thing. When in doubt alway do a 'show ip bgp
regexp <regular-expression>' to confirm what your output will be before
configuring or applying the as-path access-list.
+ says, 1 or more sequences of the pattern and ? says 0 or 1 occurrence of
the string pattern, when you combine both of them together as in the first
as-path list, you will get the lest specific which will be 0 or 1 occurrence
of the matched string pattern.
* says 0 or more sequence of the string pattern.
HTH
Godswill Oletu
CCIE #16464
----- Original Message -----
From: "Sami" <sy1977@gmail.com>
To: "ccielab" <ccielab@groupstudy.com>
Sent: Sunday, July 02, 2006 6:17 PM
> It has been discussed several times, allow AS 4 and it's directly
connected
> customer. I always use this regexp
>
> *ip as-path access-list 1 permit ^4(_[0-9]+)?$
>
> *but Cisco DOC CD says
>
> Only Allow Networks Originated from AS 4, and ASs Directly Attached to AS
4,
> to Enter Router 1
>
> If you want AS 1 to get networks originated from AS 4 and all directly
> attached ASs of AS 4, apply the following inbound filter on Router 1.
>
> *ip as-path access-list 1 permit ^4_[0-9]*$*
>
> router bgp 1
> neighbor 4.4.4.4 remote-as 4
> neighbor 4.4.4.4 route-map foo in
> route-map foo permit 10 match as-path 1
>
>
> Is there any diffrence between these two ? if both are same , then I
should
> save some brain cells and use the simple one *^4_[0-9]*$*
> **
> *Comments ?*
>
> Thanks
>
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