Cell Relay Archive

[noemi@access1.digex.net (Noemi Berry)]

>There're 3 or 4 Fore ASX 200 switches that we have access to. We have
>them connected "sequentially" using IISP. All hosts connected to each
>switch are on the same IP subnet. The "last" of these switches is then
>connected to a Cisco router, which has a wire going to another Fore
>switch, an Asx 1000, which connects us to the internet backbone. Hosts
>connected to the Asx 1000 are on a different IP subnet from the one for
>the other switches.
>
>What is the "best" way to bypass the router and connect the Asx 200
>switches to the Asx 1000 directly?

What is your goal in bypassing your router?  Is it to get the
ASX200-connected hosts talking directly over ATM to the ASX1000-
connected hosts?

If so, there are any number of things you can do, depending on your intent.

First connect the ASX-200 and ASX-1000 physically.  Turn on some
or other routing between them (SPANS, PNNI, static, whatever).

Figure out the logical IP arrangement.  If you want all your hosts
on one IP subnet, you can renumber one set of hosts.  Or, use
a logical subinterface on every host and create a new IP subnet
(multihoming them).  (Fore adapters let you do this, I assume
others do too).  You can even add an ATM subinterface on your Cisco
to route to this new subnet.

Then, dthe IP/ATM address resolution.  ARP service is the easiest way,
if all your hosts are ATM-attached and you don't need broadcast.  Use
LANE if you need broadcast or want to add ethernet hosts to this subnet.

If you really want the hosts on different IP subnets, then you
need to route between them, which you already are.  An alternative
is to run Fore IP/SPANS across them and configure gateway routes
in your hosts, but this violates all the good things that routers
do and has a high likelihood of causing problems later.

Then there's NHRP and MPOA, but if you're looking to connect your
ATM-attached hosts today, you can do some or other version of the
above and have them all talking to each other in an afternoon.

(If you were hoping to attach the ASX200 into the ASX1000 and bypass
your Cisco to get one hop closer to the Internet, that's different.
That'd be no different than moving a host from behind your Cisco
directly to, say, an FDDI ring that your Cisco and your ISP's router
share.  The layer 3 is the sticky part, not the layer 2, and you'd
have to ask yourself what that really buys you.)

noemi
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Noemi Berry					email: noemi@access.digex.net
AT&T DISC/DREN Architecture Team		voice: (703)471-3688
Herndon, VA                                       fax: (703)471-1575
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