> From: Paveza, Gary <[log in to unmask]>

> I'll confess right from the start that my knowledge of networking is very
limited and
> was hopping someone on the list could help clarify somethings for me.

I'll take a shot... [excuse formatting of included text... stupid MS IE...]

> We currently are running an HP3000 with one 10 mbs lan card, configured
as LAN1 with a B class address, configured off the system bus.  We recently
purchased two 100 mbs lan cards which we will be installed (hopefully).
[snip]

> I have talked with the Response Center and was informed that because we
have a class B address, the first two octets have to be different for each
lan card on the system.  So if I had an address of say 128.67.52.5, then
the other cards would have to be something like 128.68.52.5 and
128.69.52.5.

That would be essentially correct...

> Is the above true?  Must lan cards be on totally separate networks?  Why
can't
> they be LAN1 = 128.67.52.5 LAN2 = 128.67.52.6, and LAN3=128.67.52.7?

Going strictly by the book, this would be true.  The basic TCP/IP stack is
incapable of traditional "load sharing" such as you suggest.  When a host
wishes to connect to you, sure you can specify a TCP/IP address and get a
specific card, but now how does the host handle getting back to you?  It
could reach you over any one of the three cards -- which one?  how does it
choose?  The routing information for the layer 3 connection is the same.
Only if they are on unique networks is the routing information obvious and
the answer unambiguous.

Sitting on different networks can also be an issue since you have the
option of acting as a router between the connected networks (the function
of unix routed daemon).  On the 3000 you can accomplish a bit of this by
setting store-and-forward buffers greater than zero, but if you're using
multiple interfaces in a firewall fashion you may not wish to do this.

One option you *do* have is to dedicate one of the LANICs to DTC traffic.
Configure that LANIC for DTS use and don't give it an IP address.  This
isn't ambiguous as the DTC traffic is layer 2 and does go to a specific
card, and the outbound traffic is also unambiguous.

The only current means of boosting your network bandwidth to a single
network with multiple interfaces is to group similar LANICs and feed a
Cisco Catalyst switch with ports setup for "etherchannel".  This takes some
host-side driver tweaking and will not likely appear for the 3000, though
it was recently announced for the 9000.  In this scenario the traffic is
indeed load-shared across the links (up to 4 100Mb links can be clustered
this way) but I think the traffic is multiplexed by MAC address, i.e., it
load-shares on a connection, rather than a packet basis.  In any event, you
present only one IP address to the network layer, and the layer 2 drivers
on either end handle the load sharing.

You *might* be able to subnet your class B to separate the networks, and
alias your DNS name to the various IP addresses assigned to the interfaces,
but that's just a best guess (and something I've never done).

Jeff Kell <[log in to unmask]>