[52631] in North American Network Operators' Group
Re: iBGP next hop and multi-access media
daemon@ATHENA.MIT.EDU (jlewis@lewis.org)
Mon Oct 7 15:05:49 2002
Date: Mon, 7 Oct 2002 11:24:52 -0400 (EDT)
From: jlewis@lewis.org
To: Ralph Doncaster <ralph@istop.com>
Cc: "E.B. Dreger" <eddy+public+spam@noc.everquick.net>,
"nanog@merit.edu" <nanog@merit.edu>
In-Reply-To: <Pine.LNX.4.21.0210070006230.1709-100000@ns.istop.com>
Errors-To: owner-nanog-outgoing@merit.edu
On Mon, 7 Oct 2002, Ralph Doncaster wrote:
> > > > As others are saying... it isn't "local". It's not "local"
> > > > unless in the same subnet. Physical topology often correlates
> > > > with higher layers, but it's not strictly 1:1.
> > >
> > > Manually configuring a static route in router A would achieve the result:
> > > ip route 172.16.16.0 255.255.255.0 fa0/0
> >
> > Why are we doing basic IP routing 101 on NANOG?
>
> OK, since it's so basic why don't you explain how to have router A
> dynamically learn from router B that there is a new subnet on the local
> ethernet?
You don't. Even if you did somehow manage that on the routers, how will
the hosts get packets back to a router for which they have no route?
With no route to get packets back to the router, they're going to use
their default route. Or you could write your own IP stack. I have a
friend who did this for a networked environmental probe. Rather than
utilizing IP routing, this device's primitive IP stack simply sends
replies to the MAC address from which they came. I suspect the IP stack
on Cisco switches may do something similar. I don't think you're going to
find this functionality in many 'normal' IP stacks.
> > Don't route IP blocks to the ethernet. That's using ARP as your routing
> > protocol and it's horribly fragile. I've seen one ISP do that (they were
> > very technically challenged) and it's a setup that broke way too easily.
>
> So then what do you call a connected route (for an ethernet interface on a
> router)? If you use ethernet, at the edges of your network you HAVE to
> route IP blocks to the ethernet.
I don't have to. Go ahead and do it your way.
----------------------------------------------------------------------
Jon Lewis *jlewis@lewis.org*| I route
System Administrator | therefore you are
Atlantic Net |
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