Operating System - OpenVMS
Showing results for 
Search instead for 
Did you mean: 

Identifying Cisco router in NCP?

Geoff Hess

Identifying Cisco router in NCP?

When allowing routing between two or more DECnet areas in a WAN, is there any way to use NCP to identify the Cisco router that is routing the DECnet packets between the LANs?
The switch is a Cisco Series 3800 router (connected to a Cisco Catalyst 4500 Series switch).

Honored Contributor

Re: Identifying Cisco router in NCP?

Interesting question.

I'll assume you know that the DECnet router operating between LANs is the area router, of course, and that you have multiple area routers here.

DECnet can use multiple paths (circuits) in parallel, can use multi-path failover, and (depending on the LAN set-up) does not even require a DECnet router to operate.

DECnet does monitor its adjacencies, certainly.

Unfortunately for the discussion, DECnet end-nodes are sometimes more powerful and capable than might be expected, and, well, sometimes somewhat less capable. For instance, two end-nodes that can see each other can chat directly. No DECnet routers needed.

What's the background here on the problem?

Depending on your particular goals, the router priority can be adjusted, for instance.

If your goals are around the cost of the Cisco routing, you can potentially switch to DECnet-Plus and route your same application stuff via IP; this requires no application changes. This presumes your OpenVMS version and such support it. Swapping the DECnet stack and the associated network re-configuration, and off you go.

The other approach (again, depending on your goals) is to see which Cisco DECnet area router is busy.

For details of how DECnet routing works, the routing specifications are available. Among other places, they are available here:


And yes, I am providing a rather scattered answer, as I am not certain what your goal(s) here might be.

Ok. Third try at posting this. I *love* ITRC. Not.
Geoff Hess

Re: Identifying Cisco router in NCP?


Thanks. My networking knowledge is limited, so bear with me.

BACKGROUND: My question stems from a desire to understand how DECnet routing works in this WAN environment in order to prepare for, and test imminent changes planned by corporate network engineers (byw, they don't seem to know much about DECnet...).

This is the multiple-area network:

(EN location)
25.x ---+
21.x |
WAN --- 20.x ("LB" location)
28.1 ("KC" location)

I'm located at the "EN" location having DECnet areas 25 and 21. These LANs go into a Cisco 4500 series switch and get out to the WAN via a Cisco 3800 router and T1 hardware. (I presume there's similar hardware for the remote LANS (areas 20, 28, 63).)

If I do an SHOW KNOWN NODES command in NCP from node 25.1 (an area router), I see all the nodes in the DECnet areas pictured, but it doesn't seem to show me anything to identify the Cisco router. Maybe this is transparent to DECne

The following are the changes that the network engineer is planning. There is at least one VAX (maybe another) plus a couple of old (but critical) DECnet/SNA gateways at the location where they plan to do this work. I want to make sure that when the cable switch occurs, nothing breaks. I do not know how to answer his question concerning whether or not the system caches the router's MAC address.

"We will be moving the network cable for the KC Vax to a different switch. We will then move the router interface. As long as the Vax in KC does not cache the router's mac address everything should work fine. We run across some Sun servers that cache the router's mac address for sometimes an hour or more. We usually have to reboot them to get them moving again. Unfortunately, we do not have any examples to know if the Vax will move over to the new router easily or not."

Honored Contributor

Re: Identifying Cisco router in NCP?

Well, I'd call in help. Designing and testing a network is a fair project, even for an old DECnet network. Mix in SNA, and stuff gets more interesting.