From: yogi Bear (ryogesh@xxxxxxxxxxx)
Date: Thu Sep 28 2000 - 23:03:44 GMT-3
Abdul..
Additive is used to add a Community to Already existing community.
Pls refer the following URL for details
http://www.cisco.com/warp/public/459/15.html
Thanks
yogi
>From: abdul_rahim@ccsi.canon.com
>Reply-To: abdul_rahim@ccsi.canon.com
>To: "Mark Lewis" <markl11@hotmail.com>
>CC: kbaumgar@cisco.com, ccielab@groupstudy.com
>Subject: Re: BGP community attribute
>Date: Thu, 28 Sep 2000 18:23:30 -0700
>
>
>Hi guys
>I didnt understand whats this attribute called additive ? Can any one shed
>a lttle bit more light on it with some eg preferably or redirect me to a
>URL
>Rest all information mentioned below is very very helpful
>Thanks
>Abdul
>
>
>
>
>"Mark Lewis" <markl11@hotmail.com>@groupstudy.com on 09/27/2000 11:45:39 PM
>
>Please respond to "Mark Lewis" <markl11@hotmail.com>
>
>Sent by: nobody@groupstudy.com
>
>
>To: kbaumgar@cisco.com
> ccielab@groupstudy.com
>cc:
>Subject: Re: BGP community attribute
>
>
>Watch out! You've just given a definition of the 'no-advertise' community
>attribute.
>
>No-export - don't advertise to eBGP neighbors. (This route will not go
>outside the AS).
>
>No-advertise - don't advertise to ANY other routers (iBGP or eBGP).
>
>Community attribute can also take the form of a number. You set (tag) the
>route with a number & then filter later based upon that number.
>
>You can have combinations - you can set 'no-export' on a route, and by
>using
>the keyword 'additive' you can set additional community attributes on the
>same route (ie. set community xxx additive).
>
>Don't forget to send community attrib.s to neighbors (if thats what you
>intend!). Use the command 'neighbor xxx send-community'.If you don't use
>it,
>the community attrib. doesn't get sent!
>
>Also, watch out for community attribute affecting the advetisement on
>aggregate route with 'as-set' keyword. If one of the routes is,for example,
>'no-export' - the attribute doesn't get sent (various
>ways around this - resetting community of the route (use attribute map),
>using an advertise map to control which routes make up the aggregate,etc).
>
>Hope that helps,
>
>Mark
>
>
>
>
> >From: Kevin Baumgartner <kbaumgar@cisco.com>
> >Reply-To: Kevin Baumgartner <kbaumgar@cisco.com>
> >To: masalmon@cisco.com
> >CC: ccielab@groupstudy.com
> >Subject: Re: BGP community attribute
> >Date: Wed, 27 Sep 2000 21:26:35 -0700 (PDT)
> >
> > Actually the examples of have seen more commonly used are setting
> >the community no-export. What happens then is the route 0.0.0.0 will
> >be sent to BGP neighbor router 2.2.2.2. Router 2.2.2.2 will not forward
> >the 0.0.0.0 route on any neighbor routers.
> >
> > Also need to add "neighbor 2.2.2.2 send-community" in your
>configuration.
> >
> > A excellent book on BGP with configurations is Internal Routing
> >Architecures by Bassam Halabi.
> >
> > Kevin
> >
> > >
> > > Hey guys, I need some help with something. CAn someone explain for me
> > > the community attribute. I understand that it can be used to control
> > > which routes are sent by a downstream router to its downstream
> > > router(s). However, see below really confuses me. Can someone
>explain
> > > it? THanks.
> > >
> > > Assume that on Router C you want to set to 300 the community attribute
> > > of outgoing updates for network 170.10.0.0. The following
> > > commands apply a route map to outgoing updates on Router C:
> > >
> > > !Router C
> > > router bgp 300
> > > network 170.10.0.0
> > > neighbor 2.2.2.2 remote-as 100
> > > neighbor 2.2.2.2 route-map SETCOMMUNITY out
> > > !
> > > route-map SETCOMMUNITY permit 10
> > > match ip address 1
> > > set community 300
> > > !
> > > access-list 1 permit 0.0.0.0 255.255.255.255
> > >
> > >
> > > Access list 1 denies any update for network 170.10.0.0 and permits
> > > updates for any other network.
> > >
> > > FYI it is from the BGP section of the Cisco CD.
> > > --
> > >
> > >
> > >
> > > Mark Salmon
> > > Network Support Engineer
> > > SBC OP HQ
> > > Cisco Systems Inc
> > > 8735 W. Higgins Road
> > > Suite 300
> > > Chicago IL 60631
> > > Phone:773-695-8235
> > > Pager:800-365-4578
> > > email: masalmon@cisco.com
> > > Empowering The Internet Generation.
> > >
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