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1 NIC 2 different subnet address.

By idarmadi ·
Dear Guru,

Can I assign 2 different subnet ip address to one NIC? (Windows 2000 Server).

i.e: 192.168.4.1 and 192.168.100.3 to one nic.

Both address are meant to access the third public address assigned to a second nic. (routing using WinRoute).

I told the 192.168.100.x sysadmin that he should have another NIC in his computer to route his 192.168.100.x to my 192.168.4.x.
He said I just put the 192.168.100.x address to my NIC. It works, but I'm just wondering of any side effect thatmight occur.

TIA
idarmadi

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Pefectly valid

by LordInfidel In reply to 1 NIC 2 different subnet ...

This is a valid scenario.

What happens is that an entry is put into your routing table by the OS that says (small version, your table will look bigger)

0.0.0.0 mask 0.0.0.0 gwy (gwy ip) int 192.168.4.1
192.168.4.0 mask 0.0.0.0 gwy 192.168.4.1192.168.4.1
192.168.100.0 mask 255.255.255.0 gwy 192.168.4.1 int 192.168.4.1

Anything bound for then net will go out over interface 1.
Anything bound for the 4.0 netwk will go out over interface 1.
anything bound for 100.0 netwk will go out over interface 1 using gatweway 4.1

Your NIC will answer any requests on 100.3 ip because that address is bound to it.

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Advanced TCP/IP props

by ghstinshll In reply to 1 NIC 2 different subnet ...

Right-click on my network places
Right click on the LAN Connection icon
choose properties
double-click on TCP/IP, properties
click on the advanced button
click add, and add the 2nd IP to this...

This is how you do it, but the only concern is that people might be able to route across one NIC's subnet to the other... In NT4, there was a box to check called "enable IP forwarding", but I don't see any settings like this. I don't have a 2000 machine that i can play around with right now, but watch for a setting like that if it's in 2000 and disable it.

Would someone else please fill this in for me? Thanks.

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Routing in 2k

by LordInfidel In reply to Advanced TCP/IP props

In nt4 there was the checkbox in both wkstn and server that allowed for routing.

In 2k they did away with it. You can no longer route (using the old method) in 2k pro. They now have Internet Connection Sharing, but that is for modem style connections and all client machines must be set to dhcp.

There is no option for IP Forwarding in 2k pro.

In 2K server this now falls under Routing And Remote Access which is an MMC snap-in.

Like I said though in my other post.... Binding 2 ip's from diff subnets onto the same card does not present an issue. Your adpater will answer any request that it is set to listen for.

It will be able to get back out because it sets up a static route in it's routing table to say how to get out, and it will use the primary gateway to get back out.

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Thanks

by idarmadi In reply to Routing in 2k

Lord,

Thanks for the clarification. I was worrying
that 2 different subnet address in a NIC will
confuse it (in the long term).
Aparently I was too paranoid.

regards,
Indramin

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No problem

by LordInfidel In reply to Thanks

While routing may appear to be some big bad ugly beast (and it can be) once you learn and understand it, it is actually quite easy.

There are a few basic concepts and you just build upon them.

Just in case you did'nt understand the routing table I showed you in the 1st post, you can start up a command prompt, type in route print <enter>
and you will see your routing table.

it basically breaks down like this (for win)

destination net/ip | subnet mask | gateway | interface | hop (or metric) count

All systems will have a default route out (linux and pc alike that are running tcp/ip)

it looks like this:

0.0.0.0 mask 0.0.0.0 gateway IP Interface 1

This says to get out to the world, use the IP of gateway on interface (IP/Name) with a metric of 1.

Everything else is built around that. (you also have a localhost route, but I won't get into that here)

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