kls@ditka.UUCP (Karl Swartz) (08/22/90)
The following diagram is a greatly simplified version of my current
network configuration:
+-------+ +-------+
| Sun | | VAX |
+-------+ +-------+
| |
Ethernet A ------+---------+------------+------ ...
|
|
The +---------+ +---------+
Internet ----| cisco | | Sun-4 |
+---------+ +---------+
| |
| |
Ethernet B ------+---------+----+-------+------ ...
| |
+-------+ +-------+
| Sun | | VAX |
+-------+ +-------+
Ethernet A has a class B IP address and supports several hundred
machines, carrying DECnet, Appletalk, XNS, and probably other
stuff in addition to IP traffic. Physically it is broken into a
number of segments connected via bridges. Addresses are assigned
with subnets in mind though at present everybody (except bridges
and the cisco router) thinks the network is not subnetted.
Ethernet B is one of these subnets. With the cisco doing proxy
ARPs, machines on this Ethernet haven't a clue that they aren't
on the main Ethernet. Nothing exciting so far.
But now I'd like to put a second Ethernet board in the Sun-4 that
is our server and connect it to Ethernet A. This guy is a server
for machines on both Ethernets and for various reasons having a
direct path to both nets seems to make sense. (It won't publicize
these paths -- traffic from other machines will go via the cisco.)
How do I configure the two ports? In particular, will the netmask
influence the broadcast address (since everybody else thinks the
broadcast address matches a full class B broadcast I don't want
the netmask interfering) and what is the simplest way to handle
the (static) routing?
Here's my first stab:
ifconfig le0 134.79.112.16 netmask 255.255.240.0 broadcast 134.79.255.255 #B
ifconfig le1 134.79.16.104 netmask 255.255.0.0 broadcast 134.79.255.255 #A
Will the broadcast be what I say or will it be changed according
to the netmask and address?
And can I get away with being clever, having two routes to the
134.79.112.0 subnet? I'm hoping that the software will see le0 as
a better way to get to one part of the net reachable via le1, though
I'll be quite surprised if it actually works. The alternative is
something like
ifconfig le1 134.79.16.104 netmask 255.255.240.0 broadcast 134.79.255.255 #A
route add 134.79.32.0 134.79.16.104 0
route add 134.79.48.0 134.79.16.104 0
...
which I'd just as soon avoid if feasible.
Any answers as well as pointers on other things I might have missed
will be greatly appreciated.
BTW, for what it's worth, the Sun-4 server is a SPARCserver-390 and
is currently running SunOS 4.1.
--
Karl Swartz |UUCP uunet!apple!zygot!ditka!kls
1-408/223-1308 |INet zygot!ditka!kls@apple.com
"I never let my schooling get in |BIX kswartz
the way of my education."(Twain) |Snail 1738 Deer Creek Ct., San Jose CA 95148