From: Narbik Kocharians (narbikk@gmail.com)
Date: Sat Jan 05 2008 - 17:18:25 ARST
let's say that ISP-1 forces its client ISPs to communicate the BGP
attributes via the community tags, one way to ensure that the community tag
is coming from a given AS is to ask that AS to send the community tags
starting with their AS number followed by the actual tag, that way the
receiving AS will know that the tag/s actually came from that AS and that AS
only.
On 1/5/08, shiran guez <shiranp3@gmail.com> wrote:
>
> by default no community is advertised until you specify
>
> *neighbor <IP-ADDRESS> send-community*
>
> also by default the new format is disabled until you specify under global
> config:
>
> *ip bgp-community new-format
>
> *now once you specified this 2 you can create something like that:
>
> !R1
> int lo10
> ip add 10.0.0.0 255.0.0.0
> int lo11
> ip add 10.1.0.0 255.0.0.0
> !
> ip prefix-list NET.10 permit 10.0.0.0/8
> ip prefix-list NET.10 permit 10.1.0.0/8
> !
> route-map SET-COMMUNITY per 10
> match ip address prefix NET.10
> set community 1:10
> !
> router bgp <AS>
> net 10.0.0.0 mas 255.0.0.0
> net 10.1.0.0 mas 255.0.0.0
> *neighbor <IP-ADDRESS> remot <AS>*
> *neighbor <IP-ADDRESS> route-map *SET-COMMUNITY out
> end
> !
> clear ip bgp * ou
> !
> sh ip bg
> !
> !R2
> !
> *ip bgp-community new-format
> !
> *router bgp <AS>
> *neighbor <IP-ADDRESS> remot <AS>*
> end
>
> this example hopefully will get you started on understanding the new
> format
> community
>
> On Jan 5, 2008 8:00 PM, <ladeegeek@gmail.com> wrote:
>
> > I just can't get my arms around how to use and implement a community new
> > format number. I've looked at Halabi and the BGP section of the TCP/IP
> > book, but can't find a reasonable amount of information to see how the
> new
> > format can be implemented. Sounds kinda basic, I know - but when I try
> it
> > in the lab the route I assign a new-format number to is not advertised
> to my
> > neighbor. Is there an assumption that when using the new-format
> numbering
> > the community is also no-export?
> >
> > Thanks!
> >
> > _______________________________________________________________________
> > Subscription information may be found at:
> > http://www.groupstudy.com/list/CCIELab.html
> >
>
>
>
> --
> Shiran Guez
> MCSE CCNP NCE1
> http://cciep3.blogspot.com
> http://www.linkedin.com/in/cciep3
>
> _______________________________________________________________________
> Subscription information may be found at:
> http://www.groupstudy.com/list/CCIELab.html
>
-- Narbik Kocharians CCIE# 12410 (R&S, SP, Security) CCSI# 30832 www.MicronicsTraining.com Sr. Technical Instructor www.Net-WorkBooks.com
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