SUMMARY: NIS Timeouts? or Something Else?

From: Tim Evans (
Date: Wed Aug 18 1993 - 07:48:16 CDT

I wrote:

>Our local network includes both dial-in terminal servers and
>a local "terminal" network for RS-232-connected terminals, from
>which dial-in and terminal-net users can connect to hosts on
>the local ethernet.
>Recently, we have seen lengthy delays in connecting to TCP/IP
>hosts (Suns and RS/6000's) from both the dial-ins and terminal
>nets, with connections (via telnet) taking 3-4 minutes to complete.
>All the TCP/IP hosts which are affected are in a single NIS domain.
>We run NIS-with-DNS, as presribed by Sun.
>Our networking folks insist this is an NIS timeout problem--
>specifically, that reverse name lookups (i.e., the TCP/IP host
>attempting to lookup the name of the terminal server trying
>to connect via telnet from its IP address) are failing. They
>tell us this is our problem (with NIS) instead of any general
>network problem. The terminal servers are *not* included in
>our NIS maps, so name resolution has to occur via DNS.
>Interestingly, once one such delayed connection has finally been
>made, subsequent ones connect instantly, including subsequent
>connections from the same terminal server to *different* hosts.
>This makes me wonder if the problem might be a router problem,
>rather than an NIS one, since the terminal servers have no
>trouble connecting on subsequent tries.
>One further reference point: this problem seems to have begun
>at more or less the same time as I upgraded my master NIS server
>from SunOS 4.1.2 to 4.1.3, restoring /var/yp from a dump tape.
Thanks to: (Per Hedeland)
Mike Minnich <>
stern@sunne.East.Sun.COM (Hal Stern - NE Area Systems Engineer) (Jan Bruun Andersen)

The short summary of a long story is that the NIS slave server to
which the clients subject to the delays had bound was not properly
doing DNS lookups for an unknown reason. I re-bound the clients
to another slave server and the problem went away. I then re-
made the slave server.

As an aside, a bit of information I picked up in pursuing this
is that while Sun's NIS-with-DNS does NIS lookups first, then
falls through to DNS, IBM's AIX (I have some RS/6000's functioning
as slave servers) looks to DNS *first* then goes to NIS.

Tim Evans                     |    E.I. du Pont de Nemours & Co.  |    Experimental Station
(302) 695-9353/7395           |    P.O. Box 80357
EVANSTK AT A1 AT ESVAX        |    Wilmington, Delaware 19880-0357

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