2 Network IPs on Same VLAN?

[Saroden]

Have two Cisco 2900's. Just starting to configure IPs and VLANS on both. Want to have 199 network communicate w/ 192 network.
1. Do I need them on the same vlan to talk?
2. Is communications possible between the IPs w/ out a router?

ie.) 199.199.199.0 /24 and 192.9.200.0 /24
THESE IP'S RANGES ARE FIXED FOR VERY SERIOUS REASONS!
- Too much to do if I had to change everything.

I thought I remembered doing this in Cisco boot camp but can't remember if the networks needed same subnet. Already know about VTP, Trunks, etc...
Thanks - Saroden

 

[jgercken]

You either need them on the same vlan or a device to route between the vlans. I would just get a 2600 series router and create 2 subinterfaces on an ethernet port. Assign them to the vlans and make the router the default gateway of the client machines. If you want to use the netbios names you will also need to create a secondary WINS server or use the router's ip-helper feature.
-Jeff ----------------------------------------
Wassabi Pop Tarts! Write Kellogs today!

 

[Saroden]

So the 199.x.x.x network CAN talk to the 192.x.x.x network all I have to do is...
1. Assign same VLAN to ports
2. enable trunking
3. done?

 

[tcvander]

Your orginal question of: Is communications possible between the IPs w/ out a router?,
The answer is No.
No matter if you have all of them in the same VLAN, still need a router.
Reason being is all of the users on the 199.199.199.0 /24 network will send all packets bound for the 192.9.200.0 /24 to their default gateway's MAC address, not directly to the MAC address for the user on 192.9.200.0 /24. You need a layer 3 device like jgercken suggested Todd VanDerwerken, CCNA, CCDA
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[AkChinJim]

To say it a different way -

Packets from different networks can fly around on the same wire. Clients from the same network can talk to each other, but can't talk to any other networks on their wire or anywhere else without the assistance of a router. So, answer to question 2 is no - different networks don't talk without a layer three router involved.

Per Todd's message, you need to setup a subinterface for each network on the router using only one physical port. Then when one network client wants to talk to another network the client will send to it's default gateway which is the subinterface address on the router. The router will route the packet to the same port, but with the new packet header info so the second network client will receive it. When the second network client wants to reply, it will send to its default gateway (the other subinterface IP address on the router). Just like different networks and routers normally work, but the packets happen to be bumping into each other on the same vlan, wire, or whatever.

If you want to set up each network on it's own vlan, you could control broadcasts and multicasts generated within each network. This is only a traffic bandwidth issue - may be a solution without a problem. If you did set up two vlans, trunk them to the router and put each subinterface in the appropriate vlan.

Hope this helps.