iBGP next hop and multi-access media

Mon Oct 7 04:46:56 UTC 2002

Are you just asking a question to get a better understanding of how
things work, Ralph or have you already put this into production and are
wondering why it doesn't work a certain way?

> -----Original Message-----
> From: owner-nanog at merit.edu [mailto:owner-nanog at merit.edu] On 
> Behalf Of Ralph Doncaster
> Sent: Monday, October 07, 2002 12:43 AM
> To: Alex Rubenstein
> Cc: nanog at merit.edu
> Subject: Re: iBGP next hop and multi-access media
> 
> 
> 
> My understanding is the route is valid as long as the interface is
> up; just like adding a secondary IP on the interface.
> 
> Ralph Doncaster
> principal, IStop.com 
> 
> On Mon, 7 Oct 2002, Alex Rubenstein wrote:
> 
> > 
> > Aha.
> > 
> > So, if you route to a ethernet interface, it will try to 
> arp for that
> > address on that subnet, even without having a local address 
> on the same
> > subnet?
> > 
> > This seems to me to be something you don't want to do.
> > 
> > Is the entire route valid as long as the router can ARP for 
> one of the
> > addresses in the routed subnet?
> > 
> > 
> > 
> > On Mon, 7 Oct 2002, Ralph Doncaster wrote:
> > 
> > > On Mon, 7 Oct 2002, Alex Rubenstein wrote:
> > >
> > > > I've been doing ip route statements going on 8 years 
> now, and I can't
> > > > imagine why ever -- and how it would even work -- you'd 
> want to ip route a
> > > > netblock with a next hop of a multi-access brandcast 
> media. As in, the
> > > > next hop is still truly undetermined.
> > > >
> > > > I guess I don't know this because I've never tried it. 
> But, how does the
> > > > router determine where to send the packets for a route 
> statement as
> > > > specified above (ip route a.b.c.d e.f.g.h f0/0) ?
> > >
> > > When you setup a secondary ip on an interface
> > >  int fa0/0
> > >    ip address a.b.c.d e.f.g.h secondary
> > >
> > > How does it determine where to send the packets?  ARP.
> > > Which is the same as adding the route described above.
> > >
> > > -Ralph
> > >
> > 
> > -- Alex Rubenstein, AR97, K2AHR, alex at nac.net, latency, Al Reuben --
> > --    Net Access Corporation, 800-NET-ME-36, http://www.nac.net   --
> > 
> > 
> > 
> 