Re: multiple subnets


stueken@xxxxxxxxxxx wrote:

we are running a private class C network with a few servers and
about 60-100 hosts. By now we use several fast ethernet switches
and a few gigabit switches to connect all hosts directly.

Is it a problem, to run an other subnet in parallel on the same
switches? If both subnets use distinct netmasks and broadcast patterns,
they should not affect each other, right? Someone else tells me,
this is not possible without using VLAN capable switches.

It will work, but most likely you will ultimately regret it. Unless you
plan on placing several machines in both subnets, I would try to keep
them logically separate. VLANs are one way to do this. I would strongly
urge that non-VLAN switches be dedicated to a single subnet unless the
switch can be partitioned, in which case each partition should be
dedicated to a single subnet.

There are a variety of reasons why you are likely to eventually regret
running separate networks over the same switches (without separating
them into VLANs or otherwise paritioning them).

One reason is security. Someone who comromises a machine will
compromise all the machines on all the networks. Gateway hijacking is a
serious problem.

Another reason is limiting the damage due to accidental bad behavior.
This includes things like broadcast storms.

There are a variety of other reasons you are likely to regret
overlapping your networks this way. The only time you won't regret it
is in a very small application (for example, overlapping a NATed home
network in private IP space with a routable office network in a
home/office type setup).

Must all traffic between both networks be routed thru a router?

Essentially, yes.

We will get a router soon, but it is fast ethernet only. So I can't
establish a gigabit connection between hosts of different subnets
any more, even if they are connected to the same gigabit switch?

Nope, that's not what switches do.

DS

.

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