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BGP regexp

What does this as-path list do, if appliead to a routemap outbound?

ip as-path access-list 70 permit ^$

ip as-path access-list 70 permit ^1234$

Thanks

Stephen

========================== http://www.rconfig.com A free, open source network device configuration management tool, customizable to your needs! - Always vote on an answer if you found it helpful
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Hall of Fame Super Blue

Re: BGP regexp

Stephen

Permits any routes with no AS ie. they originated in the local AS or an AS of 1234.

Jon

4 REPLIES
Hall of Fame Super Blue

Re: BGP regexp

Stephen

Permits any routes with no AS ie. they originated in the local AS or an AS of 1234.

Jon

Re: BGP regexp

ah yes... makes perfect sense, and has the desired effect.

Thanks Jon,

Stephen

========================== http://www.rconfig.com A free, open source network device configuration management tool, customizable to your needs! - Always vote on an answer if you found it helpful
Cisco Employee

Re: BGP regexp

Stephen,

It allows paths with an empty AS PATH (locally originated prefixes) or paths that have been originated by and received from AS 1234.

Regards

Harold Ritter
Sr. Technical Leader
CCIE 4168 (R&S, SP)
harold@cisco.com
México móvil: +52 1 55 8312 4915
Cisco México
Paseo de la Reforma 222
Piso 19
Cuauhtémoc, Juárez
Ciudad de México, 06600
México

Re: BGP regexp

Hello,

The entry that references ^1234$ allows all routes originated in neighboring AS 1234 only if the neighboring AS 1234 does not make use of prepend. If neighboring AS 1234 prepends its own AS one or more times, updates will not pass. ^1234$ means "only a single 1234 in AS path and nothing else". You need something like ^(1234_)+$ to allow all updates from neighboring AS 1234 under any circumstances.

Kind Regards,

M.

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