Mark, there is a mistake in your first ncp command: it uses SET instead of DEFINE. The ncp define command operates on the permanent database Set modifies the volatile database, somewhat similar to the way SYSGEN works where you WRITE CURRENT (define) or WRITE ACTIVE (set). What is the output of these commands: $ mc ncp show circ ewa-0 char $ mc ncp list circ ewa-0 char The example in the cluster manual tries to minimize decnet downtime. That's why it uses a set circ state off and set circ state on sequence. The state off command crashes your system for some reason. The only reason I can think of is that it is already a cluster member and a boothost. The only way to modify circuit or line attributes is to add or modify them to/in the permanent database and either reboot the entire system or shutdown decnet: $ mc ncp set exec state off Followed by $ @sys$manager:netstart. However if there are active cluster members (also in a SCSI cluster) then shutting decnet will (and must) crash the node. -----Original Message----- From: Mark Wickens <mark at wickensonline.co.uk> Sender: owner-hecnet at Update.UU.SE Date: Thu, 15 Sep 2011 11:55:36 To: <hecnet at Update.UU.SE> Reply-To: hecnet at Update.UU.SESubject: Re: [HECnet] Satellite configuration/NCP crash I tried the commands you gave, and this time it crashed again: NCP>set circ ewa-0 service enabled NCP>set circ ewa-0 state off NCP> %%%%%%%%%%% OPCOM 15-SEP-2011 11:39:48.02 %%%%%%%%%%% Message from user DECNET on SLAVE DECnet event 4.7, circuit down, circuit fault