Re: CNAT Program

2000-05-16 15:11:44
Subject: Re: CNAT Program
From: James_Shanks AT tivoli DOT com
To: nv-l AT lists.tivoli DOT com
Date: Tue, 16 May 2000 15:11:44 -0400
Look at CNAT as an address translation device.   Here's how I understand it.

Suppose your company merges with another (or you  are a network service
provider) and you suddenly have two networks to connect, each of which has
overlapping IP address ranges.  Say for example they both had  Then
you would install CNAT boxes on the routers which connect these two networks and
configure them to "translate" the duplicate ranges.  Incoming packets from would get a new address, say of, so that within each
network the existing ranges would be preserved and no one would misroute.  Only
the CNAT boxes would know what was going on and they would massage the headers
in the packets as they came and went to provide the correct addresses in each
network.  CNAT goes other vendors one better by also reading enough of the
packet to determine if it is an SNMP request or response and, if so, also
changing the addresses within that, so that  SNMP still works correctly.   Plain
ol' NAT doesn't do that.

Does this solve your duplicate IP address problem?  I don't know.  You'll have
to determine that.

James Shanks
Tivoli (NetView for UNIX and NT) L3 Support

"Prokott, Joe" <Joe.Prokott AT westgroup DOT com> on 05/11/2000 04:23:33 PM

Please respond to IBM NetView Discussion <nv-l AT tkg DOT com>

To:   "'NV Forum'" <nv-l AT tkg DOT com>
cc:    (bcc: James Shanks/Tivoli Systems)
Subject:  [NV-L] CNAT Program

Does anyone have experience with the Tivoli CNAT program?  Supposedly this
sits on top of NetView and deals with "duplicate" addresses.  Specifically,
I am looking for a way to configure NV so that it only discovers a
(potentially duplicate) private address on a single managed node rather than
on a non-desired managed node.

For example, we have some customers where we manage a single serial
interface on a router, but do not control or manage their LAN interfaces.
Some of these customers use private addressing and these private addresses
in some cases are the same as reachable and desirably-managed private
interfaces on other servers on our own LAN.  However, NetView seems to
periodically delete these interfaces from the nodes we want to manage and
move them to the router where we don't want to manage the LAN interfaces
(only a single serial interface).

Will CNAT resolve this problem?  If not, how do we get around this?  What
other functions does CNAT provide?  The blurb on the Tivoli web site is very
brief and not very helpful.

Joe Prokott
Network Architect
West Group
phone:  651-687-4536
e-mail: joe.prokott AT westgroup DOT com


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