From: Kenneth Wygand (KWygand@customonline.com)
Date: Sun Jul 18 2004 - 18:39:45 GMT-3
Looking at this from a layered approach, a few solutions come to mind.
My logic is as follows:
In order for a router in your domain to be able to respond to a telnet
packet, it must know how to get back to the source. Since the loopback
interface cannot be installed in the routing tables of the destination
devices, they can have a summary route (or default route) back to the
loopback address of the switch. This could also be a static route for
that matter, if not explicitly prohibited.
Secondly, the destination routers could learn how to get to the sourced
loopback address through proxy arp, whereas an address would need to be
installed on all destination devices that encompasses the source
loopback address as local. This can be accomplished by a secondary (or
primary) IP address somewhere so the routers arp for the source address.
Of course, this solution relies on proxy-arp at the intermediary
devices.
Another route (perhaps a summary route) could be generated to
incorporate the loopback address. Once a packet traversing this route
ends up at your 3550, it will use the longest match in the routing table
which will end up being the loopback interface (with a distance of 0 of
course).
Another solution would be to translate the source address through
NATting to another address that all destinations have reachability to.
Is there another solution I am not thinking of?
Kenneth E. Wygand
Systems Engineer, Project Services
CISSP #37102, CCNP, CCDP, ACSP, Cisco IPT Design Specialist, MCP, CNA,
Network+, A+
Custom Computer Specialists, Inc.
"The only unattainable goal is the one not attempted."
-Anonymous
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
ccie2be
Sent: Sunday, July 18, 2004 2:24 PM
To: Group Study
Subject: Sunday's Network Brain Quiz
Hi guys,
Here's an interesting challenge for all those ccie wannabe's out there:
There's a router in the middle of your network with 5 active interfaces.
It's
running a couple of different routing protocols: eigrp and ospf.
On this router a loopback interface, lo133, is configured with the
address
154.6.133.1/24 which is not known or advertised by any routing protocol.
On this same router, the command, ip telnet source-interface lo133, is
configured.
What additional configuration is needed so that telnet sessions
initiated from
this router are successful to any other router in the network?
Prove your config by showing multiple successful telnets.
Hope you have fun with this. Tim
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