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From: pha@caen.engin.umich.edu (Paul H. Anderson)
Newsgroups: comp.sys.apollo
Subject: questions on DDS network interfaces and name service
Keywords: DDS routing network interface
Message-ID: <1990Aug23.175212.29600@caen.engin.umich.edu>
Date: 23 Aug 90 17:52:12 GMT
Sender: news@caen.engin.umich.edu (CAEN Netnews)
Organization: The University of Michigan, Ann Arbor
Lines: 67


I have several questions about putting one Apollo host on two
different networks via two different ring cards.  The intention
is to provide greater availability for the fileserver, and to
avoid fileserver traffic across a gateway.  The node is not
routing traffic itself, although it does have two interfaces.

Each interface is given a unique name, to allow the nameserver
to hold both.  The nameserver might have the following registered
in the ns_helper database:

	bigfs	1.9876
	bigfs_2	2.9876

Therefore, nodes may access node 9876 through one interface
or the other, depending on which one it uses the very first
time (see question 2, below).  Thereafter, any reference to
either bigfs or bigfs_2 goes through the interface specified
the very first time.

Q1:  It appears that when one the network on one interface
goes down, that access to the fileserver on the other interface
also gets wedged, even though the second network is still up.
Am I doing something wrong, or is there no way around this?

This is a potential problem, because we would like to implement
an alternate network for large fileservers for robustness, but
if the alternate net can't access the alternate interface just
because one of the primary rings goes down, then we don't benefit.

Q2: Currently, when a new client comes on the net, then looks
at the fileserver through one interface, it uses that interface
ever after, even with the alternate interface name.

I am able to change the interface that a client resolves to by
removing the /sys/node_data/hint_file, then rebooting the node,
then touching the interface that I want to use, first.  After
this is done, the client machine always uses that interface.

I tried various combinations of ctnode and modifying things
in the name server, but nothing did what I wanted.

Why do I want to do this?

Two scenarios come to mind:  1) we move a fileserver from one
ring to another, and change the network adress, and 2) we have
two interface cards on a fileserver, and for some reason want
to be able to 'point' a client to one interface or the other.

In the first case, I believe that I must reboot every client
machine that wishes to see that particular fileserver, and
this can be a monumentally expensive task with 500 clients,
any one of which might access the fileserver.  The second case
still requires a reboot of the client node.

Is there a safe way for me to dynamically modify the hint_file to
use a different network number for a given node id?

I've spent the last day or so experimenting with different
configurations, and I'd like to figure out exactly what the
limits are to the things I'm trying.

Thanks in advance for any answers.

Paul Anderson
CAEN Systems Programmer
University of Michigan