NSCLIENT - Connection refused under load?

[Steve Shipway]

>When we increase the number of checks on NSCLIENT above 
>approxmiately 15 or 
>so, we start receiving "Connection refused by host" from 
>check_nt on the 
>Windows box(es) we're trying to monitor.  These connection 
>refused messages 
>seem to happen fairly randomly.  We also receive what appear 

Yes, we get this as well on network-busy servers.  We are using pNSclient
v2.0.1.0.

As far as I can tell, this is only happening on our more busy servers, and
seems to be an issue with the TCP stack running out of resources.  We are
experimenting with changing the registry settings on the server, and so far,
this appears to have fixed it.  The registry changes/additions we made are:

hkey-local-machine
system/currentcontrolset/servicse/tcpip/parameters
maxUserPort = 0xfffe
tcpTimedWaitDelay = 60

This allows the system to have up to 65534 TCP ports active at once, and
re-uses them after 60 seconds of closure (default is 4 minutes).

These changes were very necessary under NT4/2k for any server with frequent
small connections (proxy servers, mail relays, etc) and the same problem has
affected out Citrix servers with heavy pNSclient monitoring.

However, YMMV.  Test it first :)  Don't know about XP/2k3. HTH, HAND.

Steve

---
Steve Shipway: ITSS, University of Auckland
Email: s.shipway at auckland.ac.nz  Web: http://www.steveshipway.org/  
** We can only discover new oceans when we have the **
** courage to lose sight of the shore.              **
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