[j-nsp] Route Advertisement using Communities.

Dan Benson dbenson at swingpad.com
Fri Mar 4 16:26:07 EST 2005

I am currently using communities to advertise customers routes to my 
upstream providers globally, but as my network grows I want to be able 
to have my customers choose what carriers their routes are set to and 
where.  In my lab, I am making policy statements that will take my 
customer routes, Tagged as say 65000:1001, and advertise them.  The 
customer routes are tagged on the edge router that the customer peers 
with to allow us to redistribute this to our peers and upstream 
networks.  This is all working perfectly, now what I am trying to do is 
allow for the customer to tag the routes they send to us as well, and 
depending on the tag they send, have my network handle the route 

Example:  I have a route from a customer BGP session, say AS65555, route My network's edge router tags the route with a community 
65000:1001  .I want the customer to be able to tag the routes with 
additional communities to allow the customers routes to be advertised in 
certain places or not.  In this case, the customer tags their route with 
a community of 65000:2003.  On my edge routers that connect to my peers 
and my upstreams, I will see the route as with the 
communities of 65000:1001 and 65000:2003.  When I try and tell my 
routers to advertise the route based on the first tag, 65000:1001, they 
do just fine.  The Second I try and drop a route because of another tag, 
it continues to advertise the route.  I am assuming this is because I 
accept on the first tag and then try and drop on the second.  I would 
have assumed that the hierarchy of my terms would follow suit, but this 
does not seem to be the case.  Example of my policy statement:

    policy-statement peer-0 {
        term 5 {
            from community customers;
            then accept;
       term 10  {
             from community no-att-global;
             the reject;
        then reject;

community no-att-global members 65000:2003
community customers members  65000:1001

Thanks in advance for the assistance..   //db

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