topic Re: IP router redundancy in Operating System - OpenVMS

IP router redundancy

Wim Van den Wyngaert — Thu, 09 Sep 2004 08:14:03 GMT

I have a node with 1 default gateway A.
Now suppose I have a 2nd gateway B going thru the same interfaces.

I have setup the routing table in such a way that B comes for A. B is non-existing.

I do a ping of C, which is behind the routers A (and B but B is not there). Result : device timeout after about 15 seconds.

I redo the ping : working correctly.

I redo the ping : timeout.

So, there is no failover or is my IP bad configured ? Does anyone has pointers to a description of the algorithme ?

Wim

Re: IP router redundancy

Antoniov. — Thu, 09 Sep 2004 09:28:28 GMT

Wim,
may be interesting use traceroute command.

Antonio Vigliotti

Re: IP router redundancy

Wim Van den Wyngaert — Thu, 09 Sep 2004 09:32:14 GMT

Antonio,

Since the node B doesn't exist, it will not respond to ARP and thus not to tracerout.

It concerns TCP 5.3 and I found in the release notes that it is normal behaviour (round robin without retry, thus 1 out of 2 usages fail).

But why ???

Re: IP router redundancy

Ian Miller. — Thu, 09 Sep 2004 10:11:48 GMT

do the routes have the same cost?

Re: IP router redundancy

Wim Van den Wyngaert — Thu, 09 Sep 2004 10:13:14 GMT

Ian,

Cost ? In IP ?
So, yes ...

Re: IP router redundancy

Wim Van den Wyngaert — Fri, 10 Sep 2004 07:13:02 GMT

I refrase.

There is an RFC816 that specifies how to handle failed routes. E.g. by doing retransmit on the next available route.

Why is this not done on VMS ?

Re: IP router redundancy

Wim Van den Wyngaert — Fri, 10 Sep 2004 07:17:37 GMT

I tested it on 4.2 eco 1 too.

There no round robin is done. The first route is taken and that's it.

Wim

Re: IP router redundancy

Gib Copeland — Fri, 10 Sep 2004 15:24:37 GMT

Configure your routers to advertise a default route. Enable RIP on the router and on VMS (gated). Delete your static default gateway route. Gated will choose a default route, and if the router goes away, it will time-out and switch to the other router.