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Operating System - OpenVMS
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ARP settings and problems in OpenVMS

 
Piet Timmers_1
Frequent Advisor

ARP settings and problems in OpenVMS

We have three OpenVMS nodes, TCPIP version OpenVMS Alpha Version V5.0A, in one location, and on one switch.
The network provider has changed some settings for the network. Two nodes cannot be reached, one is normal.

The network provider has disabled ARP-PROXY.
What can we do to get everything working, whithout using ARP-PROXY?

Thanks.

Piet
7 REPLIES
Oswald Knoppers_1
Valued Contributor

Re: ARP settings and problems in OpenVMS

I am not sure i understand your network configuration.

Are all three nodes connected to the same switch? If so, i fail to see what arp-proxy has to do with it.

Oswald
Piet Timmers_1
Frequent Advisor

Re: ARP settings and problems in OpenVMS

Oswald,

Thats also my problem.

They disabled ARP-PROXY on a router and we had a problem reaching two out of three nodes. A windows domaincontroller, on the same switch, was reachable.

They enabled ARP-PROXY, no problem.

And yes, the three nodes are connected to the same switch.

Greetings
Oswald Knoppers_1
Valued Contributor

Re: ARP settings and problems in OpenVMS

Are all three nodes in the same (sub)net?
Can you do a '$ tcpip show arp' on all three nodes?

Oswald
Richard Brodie_1
Honored Contributor

Re: ARP settings and problems in OpenVMS

One of the things an ARP proxy can do, is to make up for a bad subnet configuration.

I suggest you review your network settings carefully, particularly the subnet mask.

Alternatively, you could take some packet captures (e.g. with Wireshark) and work out what's different. That's likely to be harder work though.
Piet Timmers_1
Frequent Advisor

Re: ARP settings and problems in OpenVMS

The output formatting is better in an external document. See attachment.

Richard Brodie_1
Honored Contributor

Re: ARP settings and problems in OpenVMS

This was a very recent change, then?

It looks like the unreachable nodes have stale proxy ARP entries:

e.g. 10.114.37.237 00-00-0c-07-ac-01

whereas the working node has an ARP entry for the gateway.

10.114.3.1 00-00-0c-07-ac-01

I think it might be OK when the stale entries timeout. A few "SET NOARP ip", to flush them, should speed things up.

Re: ARP settings and problems in OpenVMS

The problem is not that 'Two nodes cannot be reached', the problem is that two nodes (ASDS9C and PAML01) do not see their default gateway (10.114.3.1). It is not directly connected.