One machine seeing broadcast traffic from a different logical IP network

Gurus,

I thought this was odd. I have a small network of machines all running on a
192.168.1.x/24 subnet. On the same physical segment, I have another machine
who's TCP/IP settings I switched to 10.0.0.2/8. Afterwards, this machine
could no longer initiate point-to-point communications with any machine on
the 192.168.1.x subnet as expected. I also installed Wireshark on this
machine to see what kind of traffic this machine would pickup. Since it is
on a completely different logical IP network, I expected to see NO packets.
Much to my surprise, I was seeing broadcast traffic. Stuff like Browser
traffic along the lines of host announcements and Domain/workgroup
announcements. I was hypothesizing that I wouldn't see any traffic coming
across it's NIC. I'm a bit confused.

--
Spin

In article <(E-Mail Removed)>,
"Spin" <(E-Mail Removed)> wrote:

> Gurus,
>
> I thought this was odd. I have a small network of machines all running on a
> 192.168.1.x/24 subnet. On the same physical segment, I have another machine
> who's TCP/IP settings I switched to 10.0.0.2/8. Afterwards, this machine
> could no longer initiate point-to-point communications with any machine on
> the 192.168.1.x subnet as expected. I also installed Wireshark on this
> machine to see what kind of traffic this machine would pickup. Since it is
> on a completely different logical IP network, I expected to see NO packets.
> Much to my surprise, I was seeing broadcast traffic. Stuff like Browser
> traffic along the lines of host announcements and Domain/workgroup
> announcements. I was hypothesizing that I wouldn't see any traffic coming
> across it's NIC. I'm a bit confused.

Broadcast traffic is sent to all nodes on the physical segment, it's not
specific to an IP subnet.

--
Barry Margolin, (E-Mail Removed)
Arlington, MA
*** PLEASE post questions in newsgroups, not directly to me ***
*** PLEASE don't copy me on replies, I'll read them in the group ***

"Barry Margolin" <(E-Mail Removed)> wrote in message
news:barmar-(E-Mail Removed)...
> Broadcast traffic is sent to all nodes on the physical segment, it's not
> specific to an IP subnet.
>
> --
> Barry Margolin, (E-Mail Removed)
> Arlington, MA

I am now duly informed. Thanks!!!!

On Sep 28, 5:05*pm, "Spin" <S...@invalid.com> wrote:

> I thought this was odd. *I have a small network of machines all runningon a
> 192.168.1.x/24 subnet. *On the same physical segment, I have another machine
> who's TCP/IP settings I switched to 10.0.0.2/8. *Afterwards, this machine
> could no longer initiate point-to-point communications with any machine on
> the 192.168.1.x subnet as expected. I also installed Wireshark on this
> machine to see what kind of traffic this machine would pickup. *Since it is
> on a completely different logical IP network, I expected to see NO packets.
> Much to my surprise, I was seeing broadcast traffic. *Stuff like Browser
> traffic along the lines of host announcements and Domain/workgroup
> announcements. *I was hypothesizing that I wouldn't see any traffic coming
> across it's NIC. *I'm a bit confused.

Any ethernet broadcast traffic will be received by the NIC if it's on
its wire. It will then be up to the OS to decide whether to pass that
broadcast traffic to higher levels. Some network cards have broadcast
filters, in which case only traffic that passes the filter will be
handed to the OS.

If the traffic was a broadcast UDP datagram send to 255.255.255.255,
it should be fully processed by the OS. If it was sent to another
subnet's broadcast address, say, 192.168.1.255, it should be rejected
by the OS.

Wireshark will likely see any packets the network card receives,
whether or not the OS would process them. If it places the NIC into
promiscuous mode, it will see anything on the wire.

You can use VLANs if you need a higher level of isolation between
logical subnets on the same physical network.

DS

Can you use VLANs in VMWare Workstation 6.0?

On Sep 30, 1:58*am, "Spin" <S...@invalid.com> wrote:

> Can you use VLANs in VMWare Workstation 6.0?

There are several different ways you could try to do it. One would be
to configure the VLANs in the virtual machine. But that would rely on
VMWare passing the VLAN tag to the bridged interface. Another way
would be to do it in the host, for example, you could bridge the
VMWare guest to a dummy interface that's bridged to a VLAN on the main
interface.

I've never tried it, nor have I ever seen any documentation that
discussed whether that would work. I'm sure you could get it to work
with enough hackery, but there's probably a simple and supported way
to do it.

DS