On Tue, 06 Apr 2004 09:17:31 +1200, David Kirk
<davidrkirk.NOSPAM@hotmail.com> wrote:

>All of this is happening on our local LAN. Both subnets are on the
>same piece of wire, but of course they won't talk to each other
>without the router. There are no WAN links or Internet involved.

Now you tell me. This is what threw me:
"The router at the default gateway (192.168.1.251) is a Cisco 1721 set
up to pass all traffic between the two subnets."
Lacking any info on the topology, I just assumed that you were
routeing between two subnets over the internet. Grumble...

>All of our network was on 192.100.100.0/24 and I am changing all of
>the network to a 192.168.1.0/24 network. The router is only here for
>the duration of the migration.

I've done a few IP migrations in the past. I vaguely recall the 2nd
one was done in stages, with a temporary router similar to your
method. There's some networking book that recommends doing it that
way. What happened was the Cisco expert spent the entire weekend
bludgeoning the router and networks into some semblence of
functionality. Fortunately, it was over a weekend. By the 11th hour
(actually 23rd hour), the router expert was still having a bad day. I
finally decided that it wasn't going to work and manually reconfigured
about 100 desktops in 3 locations. It took the rest of the night, but
on Monday morning, everything worked. I turned off the router.

>Here is how I am handling the migration. Each box retains their old
>192.100.100.x address and also gets an alias address of 192.168.1.x.
>I update DNS with the new address and once everyone's DNS caches have
>expired, I remove the old address.

Don't forget the WINS cache, NETBIOS name cache, various HOSTS and
LMHOSTS files, etc. Yeah, great idea. I've done it that way and
managed to "forget" necessary changes. The problem is that everything
had to get fixed twice. Once to get the multi-address configuration
to play, and once again when I had to get rid of it. Is there a
reason you can't just change everything at once? Why prolong the
ordeal?

I vaguely recall that there was some kind of bug in the alias
mechanism in 3.2v5.0.4 that was later fixed. I'll dig when I get to
the office (timer permitting).

>The JetDirect is still set to use DHCP. The address hasn't changed
>since the printer was installed. When I move it to the other subnet
>it will have a static address.

Well, if it's currently set for DHCP, are you sure that it has the
right address? My nightmare was having multiple DHCP servers running
on a LAN. It happens almost every time someone tinkers with a
wireless router. I have arpwatch running to detect such problems on
mission critical networks. Lately, I've been using "static DHCP" to
assign IP addresses to print servers. The idea is to build a table of
MAC address and IP address pairs in the router that's running DHCP,
and reserve the IP's for those devices. I haven't figured out an
effective backup scheme in case the DHCP server dies, but that hasn't
been much of a problem with long lease times.

>Unfortunately (?) I can't test it at the moment because it all works
>and I don't know how to replicate the fault other than wait until
>tomorrow morning :-( I can answer some of them from my previous
>testing though.

Well, if it's intermittant, then it's probably the RIP1 (routed)
problem. That means you have a router or server on your LAN that's
spewing RIP announcements. Find and disable. It will break other
devices.

>There is only 1 router with 2 interfaces (1 for each subnet).

With every IP port transparently routed between both networks?

>Yes, very logical. I will have another go at this next time it fails.
>Because it is the SCO box that is the problem though, I think I should
>probable see what I can ping from the SCO box. Eg. localhost, another
>host on same subnet, router local interface, router remote interface,
>host on other subnet. That should more accurately find the fault.

Yep. The pattern should be obvious. I still think there's some
obscure file on the OSR5 boxes that haven't had their IP address
tweaked. I know you said you checked everything, but I'm still
suspicious.


--
Jeff Liebermann 150 Felker St #D Santa Cruz CA 95060
(831)421-6491 pgr (831)336-2558 home
http://www.LearnByDestroying.com AE6KS
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