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List:       portmaster-users
Subject:    Re: (PM) Routing Help Needed Cisco & IRX
From:       "Jim Flowers" <jflowers () ezo ! net>
Date:       2002-12-27 20:01:03
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Dick,

Thanks for your splendid response.  You really filled in a gap in my 
knowledge about routing.  I ran a traceroute on the mac address of the new 
managed router while I moved the ethernet cable from a switch port to a 
hub.  This triggered the Cisco to run through the entire /22 with arp who-
has queries.  FYI, both IRX routers and PM3 NACs responded to the addresses 
for which they had routes.

I think that this is probably basic router operation that every network 
engineer should know but I didn't.

So, thanks again.  I think I now understand it a little better.  And I agree 
with you about the managed router concept.

--
Jim Flowers<jflowers@ezo.net>

---------- Original Message -----------
From: "Dick St.Peters" <stpeters@NetHeaven.com>
To: "Jim Flowers" <jflowers@ezo.net>
Sent: Fri, 27 Dec 2002 13:50:13 -0500
Subject: Re: (PM) Routing Help Needed Cisco & IRX

> > The new provider has furnished a managed Cisco 2610 to load-balance 
multiple 
> > T-1s.  a CIDR /22 IP address block is routed to us.  The Cisco does not 
have 
> > any routing configured and has the ether0 interface bound to an IP 
address 
> > with a 22 bit prefix (ie a.b.c.1/22).  Our migration plan is to alias 
the new 
> > IP addresses to routers/hosts where possible to run both new and old 
logical 
> > networks on the same physical network segments.
> > 
> > My major concern is that the Cisco will treat all of the /22 IP 
addresses as 
> > local and initiate arp who-has queries instead of routing the inbound 
packets 
> > to the appropriate next hop IRX.  Secondly, how does the Cisco get the 
> > routing information if it is not running OSPF?
> 
> If the IRXs were Ciscos, they would respond to those arps. 
>  That is, if Cisco A arps for an IP address that Cisco B known 
> is at a remote site it connects to, then Cisco B responds to 
> the arp - saying, in effect, "send the packets to me, I know 
> how to route them".
> 
> This proxy arping is a sort of poor man's (or idiot's, depending 
> on your perspective) routing.  IRXs may do this also, but I've 
> never used IRX routers.
> 
> Ciscos are very good at OSPF.  If your new upstream wont' let 
> you have the Cisco integrated into your OSPF, they may have 
> it integrated into their own.  However, Ciscos can run multiple 
> OSPF processes and are perfectly happy being part of two or 
> more OSPF administrative realms.
> 
> Personally, I would never yield administrative control of my 
> router to an upstream.  Sprint configured my first router when 
> I started out some 8 1/2 years ago, but they were perfectly 
> happy letting me take it from there.  As a result, I learned 
> how.
> 
> --
> Dick St.Peters, stpeters@NetHeaven.com 
> Gatekeeper, NetHeaven, Saratoga Springs, NY
> Saratoga/Albany/Amsterdam/GlensFalls/Greenwich/NorthCreek/SaranacLake 
>    Oldest Internet service based in the Adirondack-Albany region
------- End of Original Message -------

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