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OpenVMS Systems: DECNET and Two NIC Interfaces

Posted on 2011-03-11
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Last Modified: 2012-06-22
I have a system with two NIC interfaces. The NICs are attached to CISCO switches over a multi-building campus. NIC 1 is configured for EWA0: and has an IP address configured on the 10.0 network. NIC 2 is configured for EWC0: and has an IP address configured on the 100.0 network.

The problem, an OpenVMS system across campus is on the 100.0 network and DECNET seems to be attached (Circuit is defined) to EWA0: and not EWC0:

The Circuit status is up for both connections and the line is associated with the MAC address of NIC #2 for EWC0:

How does one hard-wire DECNET to use a specific Circuit / Line / NIC interface?

I attempted a set/define node <address> name <node name> circuit EWC0 and DECNET displayed an error.

I have not tried to set the EWA0: state to disabled... but would DECNET know to connect to EWC0?  I was told DECNET broadcasts on all interfaces and selects and interface which responses to a "hello" broadcast.

Any thoughts on this?

Thanks!
 
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Question by:TimPeer
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noci earned 500 total points
ID: 35118181
DECnet has NODE addresses (a MACHINE has one address) not in interface.
IP has interface addresses... there fore a machine has at least one address per interface.

Also in IP there are separate queries done to get translations for IP -> MAC (the ARP protocol).
In DECnet the MAC address is set to a variant of the DECnet address...
==> All interfaces that are KNOWN to DECNet (ie the have a circuit & line ) definition then the MAC address is converted during boot time, to prevent MAC address change issues later on.

This causes the requirement that two interfaces of a system MAY NEVER carry DECnet in the same broadcast domain (Layer-2 (V)LAN).

If you want the interface changed then just remove the xx-0 interface and create a xx-2 interface.
The exact xx- is dependant on your interface.     if you have XXA0 & XXC0 then you have XX-0 & XX-2 respectively.

so it is:

LIST CIRCUIT XX-0 ALL
DEFINE CIRCUIT XX-2 STATE ON
DEFINE CIRCUIT XX-2 .....   (any parameters you can copy form the currnt XX-0)
LIST LINE XX-0 ALL
DEFINE LINE XX-2 STATE ON
DEFINE LINE XX-2 .....    ( Any parameters from previous XX-0)
SET KNOWN CIRCUITS ALL
SET KNOWN LINES ALL

! If you need to remove XX-0 then use the following
PURGE CIRCUIT XX-0 ALL
PURGE LINE XX-0 ALL
SET CIRCUIT XX-0 STATE OFF
SET LINE XX-0 STATE OFF
CLEAR CIRCUIT XX-0 ALL
CLEAR LINE XX-0 ALL
! The MAC address will only be cleared on REBOOT.

Replace all XX in above with the correct interface name (Probably EW).
And yes if the interface comes up it will detect other systems in the vicinity and start coomincating if they are within the SAME area. (onther wise you need an extra routing license to do level-2 routing.

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