Re: BGP Communities values

If you see BGP community from lab, it will be mostly well-known BGP
community defined from RFC1997.

http://www.ietf.org/rfc/rfc1997.txt

Otherwise, you have to use other ISP's predefined BGP community value to
control your BGP routes on their network.

Alex

Kelvin Yeo wrote:
> Thanks Ryan/Alex/Andre. I think I understand the values from a real-world
> perspective and the lab perspective.
>
> Back to Labbing...
> Kelvin
>
> -----Original Message-----
> From: Ryan West [mailto:rwest_at_zyedge.com]
> Sent: 29 May 2009 05:14
> To: Kelvin Yeo; 'Dufour, Andre'; 'Cisco certification'
> Subject: RE: BGP Communities values
>
> Kelvin,
>
> As Alex has already mentioned, providers will allow customers to send
> communities that do a number of things, giving the customer control of how
> the carrier treats the routes they receive from their customers. Common
> uses are for pre-pending of AS, local preference assignment, and temporary
> black holing. With respect to the IE, the thought process is to define
> intuitive route tags from upstream peers that are either within the same AS
> or different AS and to make route decisions based on those edge tags
> anywhere within your network.
>
> e.g. AS 54 routes from BB1 are tagged with 54:1 and AS 54 routes from BB3
> are tagged with 54:3. Those tags are used on interior routers to prefer one
> path over the other back to AS 54.
>
> -ryan
>
> -----Original Message-----
> From: nobody_at_groupstudy.com [mailto:nobody_at_groupstudy.com] On Behalf Of
> Kelvin Yeo
> Sent: Thursday, May 28, 2009 4:59 PM
> To: 'Dufour, Andre'; 'Cisco certification'
> Subject: RE: BGP Communities values
>
> Andre, thanks for your response.
>
> Let me clarify further.
>
> If I need to tag a prefix with a community values, what should it be? Should
> this value make sense when the adjacent AS received it?
>
> Ie 200:300
>
> 200 will be the originating AS while 300 is the next hop AS? Or is there any
> rationale I should consider when choosing the values?
>
> Kelvin
>
> -----Original Message-----
> From: Dufour, Andre [mailto:Andre.Dufour_at_PAETEC.com]
> Sent: 29 May 2009 04:45
> To: Kelvin Yeo; 'Cisco certification'
> Subject: RE: BGP Communities values
>
> Kelvin,
>
> To give a short summary, you can use communities with BGP in a similar
> manner that you would use tags in IGPs.
>
> The format that you are describing is the "new" community format. The new
> community is really just to make things easier to manage. You can use the
> AS#:number to make things easier than just a random number like 234353442,
> etc.
>
> Please let us know if there's a more specific question.
>
> Regards,
> Andre
>
>
>
> -----Original Message-----
> From: nobody_at_groupstudy.com [mailto:nobody_at_groupstudy.com] On Behalf Of
> Kelvin Yeo
> Sent: Thursday, May 28, 2009 4:35 PM
> To: 'Cisco certification'
> Subject: BGP Communities values
>
> Anyone can explain the idea behind assigning the communities values such as
> below
>
>
>
> 300:200 or 123:456
>
>
>
> Why is 300/123 assigned as AA while 200/456 assigned as NN in the AA:NN
> format? I mean, is there a rule to follow or design purposes? What exactly
> is it telling us?
>
>
>
> Kelvin
>
>
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Received on Thu May 28 2009 - 17:15:01 ART