At 05:17 AM 2/4/2002 -0800, andrew kevin wrote:
>Hi,Julian,
>Do you imply that the implementation of Junos is to
>advertise the ebgp routes learing from the source?
>Since the whole internet routes is 130K today,it must
>impact not only on the routers, but also the bandwidth
>for those wasting routing info.
>Why not Junos stop sending it back automatically?
>In real world, it has to manually configure the policy
>you mentioned to do the performance tuning.
>Is there some special consideration of Junos?
>Why Cisco do it default?
It is an open implementation choice. Cisco did it one
way, Juniper did it another way. As Julian mentioned,
you can configure a policy if you are overly concerned
about bandwidth of the link being affected by an extra
set of updates being send back. One of the arguments in
favor of this method is that if you are running MSDP,
this behavior is necessary to determine the upstream AS
relationship.
-Manoj
>thank,
>Andrew
>
>
>--- Julian Eccli <je@juniper.net> wrote:
> > Answers inline...
> >
> > > -----Original Message-----
> > > From: andrew kevin
> > [mailto:andrewkevin2000@yahoo.com]
> > > Sent: Sunday, February 03, 2002 8:13 PM
> > > To: juniper-nsp@puck.nether.net
> > > Cc: juniper@groupstudy.com
> > > Subject: [j-nsp] BGP route
> > >
> > >
> > > Hi,
> > > I found it's strange that BGP of Junos can't
> > follow
> > > the split-horizon rule(BGP is a DV routing
> > protocol),
> >
> > split-horizon is not used in BGP and BGP is
> > considered a path vector
> > protocol.
> >
> > > after receiving EBGP neighbors route , it will
> > send
> > > back those route which learns from the original
> > one to
> > > the source, and the original will reject these
> > routes
> > > according to the AS-PATH attribute.
> > > It will waste the router's resource to send those
> > > routes.
> > > It is different with Cisco's implementation.
> > > Cisco will not send back to the original.It seems
> > even
> > > reasonable.
> >
> > RFC1771 states it's optional to advertise or not
> > advertise back from the
> > neighbor the route is received from in section
> > 9.1.3. In a modern day
> > environment it would not matter, and should have no
> > impact on router or
> > link performance since we only send back what is
> > sent to us.
> >
> > > Or must we configure a policy to preven Junos from
> > > sending updates back?
> > > Or any better method?
> >
> > You need to set up an export policy on the peer to
> > prevent readvertising
> > back to your neighbor.
> >
> >
> > -Julian
> >
>
>
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