Can you have the same subnet on one computer with attached to two different class networks?

[rjmckay]

On the setup I want to do...

I have 2 networks feeding into one PC.

Network A = Class A
Network B = Class C

Both are currently on subnet 255.255.255.0.

Network A will be going to the gateway and therefore feeding the internet
Network C will not be given a gateway so the PC does not try to use Network C and Network A internet at the same time (and failing).

My question is... can I just simply set the networks up like this and expect it to work since Network A and B are different classes even though they have the same subnet... or will I still have to change the subnet of one of them (Likely Network A)?

Thanks!

Rj

 

[jsmithepa]

Is this a coursework question?

 

[bill001g]

You need to completely ignore the whole concept of classful networks it is not really useful other than maybe a shorthand for saying how large a network you are using.

If you are using 255.255.255.0 you are using a /24 no matter what so called "network class" you allocated it out of. You could call these class c networks but it makes it confusing. You are best off always referring to the network by the size of the mask.

Now if what you are doing is running 2 different subnets in the same lan it mostly will work as long as you do not actually overlap the same ip addresses using 2 different subnet masks. Pretty much you will just get extra broadcast packets but it doesn't really cause much issue anymore, used to be the interrupts slowed machines down but not so much anymore.

 

[rjmckay]

Is this a coursework question?

Great question jsmithepa,

It does sound like a coursework question the way I asked. But no, it's a real application question.

Let me try to describe the application.

PC-A = Network A
PC-B = Network B

We are running wirecast to stream from PC-A off of network A ... but... we need to pull shots from PC-B and from a wireless iDevice app (also Network-B).

So we need PC-A to use Network A for internet... but we need Network-B also plugged into it in order utilize Network B's LAN (outside of internet).

I was thinking of changing Network A to /23

 

[rjmckay]

You need to completely ignore the whole concept of classful networks it is not really useful other than maybe a shorthand for saying how large a network you are using.

If you are using 255.255.255.0 you are using a /24 no matter what so called "network class" you allocated it out of. You could call these class c networks but it makes it confusing. You are best off always referring to the network by the size of the mask.

Now if what you are doing is running 2 different subnets in the same lan it mostly will work as long as you do not actually overlap the same ip addresses using 2 different subnet masks. Pretty much you will just get extra broadcast packets but it doesn't really cause much issue anymore, used to be the interrupts slowed machines down but not so much anymore.

Thanks ... I only have a AAS in networking, so I only know enough about networking to be dangerous. your advice about using the size of the mask is good advice I will have to keep in mind in the future. =) Thank you.

I provided more info in another reply to this to show the application I'm trying to accomplish. (I'm also figuring out how to use TomsHardware forum for the first time too LOL!)

 

[jsmithepa]

Completely agree with bill. To me a subnet is a "range" and as long as the ranges don't overlap, I too ignore class.

 

[rjmckay]

So then to paraphrase Bill, I should be able to utilize both networks at the same time, as long as the IPs don't overlap (which they won't ... I got a 192. and a 10.) Then I should be able to use both networks at the same time as long as one of them does not have a gateway.

Or am I confused again. All networking I ever did has been much more straight-forward. =)

 

[jsmithepa]

As long as your machine has 2 NICs, two interfaces, two doors, and the doors point to a separate, non-overlapping, highways, there is no conflict, everybody happy.

Now if you have one machine with a single NIC then he can either go A or B, but can't crossover from one subnet to the other, UNLESS there is a router that sits between A and B directing the traffic.

 

[rjmckay]

As long as your machine has 2 NICs, two interfaces, two doors, and the doors point to a separate, non-overlapping, highways, there is no conflict, everybody happy.

Now if you have one machine with a single NIC then he can either go A or B, but can't crossover from one subnet to the other, UNLESS there is a router that sits between A and B directing the traffic.

Turns out exactly correct... all that complicating worrying for nothing. I just plugged in both networks (a single card with double nics) ... and that was the end of that... everything worked. Talk about over-complicating things! LOL.

Thank you both!

Rj