Conditional Advertisemet?

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-bouncespuck.nether.net 
> [mailto:juniper-nsp-bouncespuck.nether.net] On Behalf
Of 
> Chuck Anderson
> Sent: Thursday, October 05, 2006 12:19 PM
> To: Mellott, Eric
> Cc: juniper-nsppuck.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;
> }
> _______________________________________________
> juniper-nsp mailing list juniper-nsppuck.nether.net 
> 
https://puck.nether.net/mailman/listinfo/juniper-nsp
> 

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A quick test shows it does not work:

[edit routing-options]
harrylovejoy# show 
static {
    route 1.1.0.0/16 next-hop 1.1.1.2;
}
generate {
    route 1.1.1.0/30 policy test;
}

[edit routing-options]
harrylovejoy# top show policy-options policy-statement
test 
from {
    route-filter 1.1.0.0/16 exact;
}
then accept;


<<< static is active but more specific
agg/generated is not:


[edit routing-options]
harrylovejoy# run show route protocol static 1.1/16 

inet.0: 28 destinations, 28 routes (26 active, 0 holddown, 2
hidden)
+ = Active Route, - = Last Active, * = Both

1.1.0.0/16         *[Static/5] 00:09:26
                    > to 1.1.1.2 via ge-0/2/0.0

[edit routing-options]
harrylovejoy# run show route protocol aggregate hidden
extensive 

inet.0: 28 destinations, 28 routes (26 active, 0 holddown, 2
hidden)
1.1.1.0/30 (1 entry, 0 announced)
         Aggregate
                Next hop type: Reject
                Next-hop reference count: 1
                State: <Hidden Int Ext>
                Age: 9:36 
                Task: Aggregate
                AS path: I
                                Flags: Generate Depth: 0    
   Inactive

. . .

[edit routing-options]
harrylovejoy# run show version 
Hostname: lovejoy
Model: m5
JUNOS Base OS boot [7.6R1.5]

 

> -----Original Message-----
> From: juniper-nsp-bouncespuck.nether.net 
> [mailto:juniper-nsp-bouncespuck.nether.net] On Behalf
Of 
> Harry Reynolds
> Sent: Thursday, October 05, 2006 12:33 PM
> To: Chuck Anderson; Mellott, Eric
> Cc: juniper-nsppuck.nether.net
> Subject: Re: [j-nsp] Conditional Advertisemet?
> 
> 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-bouncespuck.nether.net
> > [mailto:juniper-nsp-bouncespuck.nether.net] On Behalf
Of Chuck 
> > Anderson
> > Sent: Thursday, October 05, 2006 12:19 PM
> > To: Mellott, Eric
> > Cc: juniper-nsppuck.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;
> > }
> > _______________________________________________
> > juniper-nsp mailing list juniper-nsppuck.nether.net 
> > 
https://puck.nether.net/mailman/listinfo/juniper-nsp
> > 
> 
> _______________________________________________
> juniper-nsp mailing list juniper-nsppuck.nether.net 
> 
https://puck.nether.net/mailman/listinfo/juniper-nsp
> 

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