[j-nsp] Conditional Advertisemet?

Harry Reynolds harry at juniper.net
Thu Oct 5 15:33:29 EDT 2006


Hmm. Normally a generate/aggregate route is activated by a more-specific
route, i.e., contributing prefix.  

In this case you are trying to activate a more specific generated with a
less specific contributing route, which I do not think will work. The
forwarding NH of a generated route is determined by the FNH of the
preferred contributing route. Forwarding for a /28 over a /16 could lead
to loops.


Regards


> -----Original Message-----
> From: juniper-nsp-bounces at puck.nether.net 
> [mailto:juniper-nsp-bounces at puck.nether.net] On Behalf Of 
> Chuck Anderson
> Sent: Thursday, October 05, 2006 12:19 PM
> To: Mellott, Eric
> Cc: juniper-nsp at puck.nether.net
> Subject: Re: [j-nsp] Conditional Advertisemet?
> 
> On Thu, Oct 05, 2006 at 01:59:17PM -0400, Mellott, Eric wrote:
> > Have a BGP configuration where I learn a /16 network from one eBGP 
> > neighbor and want to advertise a subset of that network, 
> i.e. a /28, 
> > to a different eBGP neighbor.  Currently, I am able to 
> advertise the 
> > subnet by configuring a static route which puts the /28 in table, 
> > however; this kills anything dynamic.  Is there a way with 
> conditional 
> > advertisements or a generate route to dynamically advertise the /28 
> > upon receipt of the /16?  Also, I don't want to rely on the BGP 
> > neighbor (who is advertising the /16) to give me the /28 instead.
> 
> This might work:
> 
> [edit routing-options]
> # show generate
> route w.x.y.z/28 policy MATCH-16;
> 
> 
> [edit policy-options]
> # show policy-statement MATCH-16
> term 1 {
>     from {
>         route-filter w.x.0.0/16 exact;
>     }
>     then accept;
> }
> term 2 {
>     then reject;
> }
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