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Help with Isolating Traffic on Different Subnets

What I have is two Cisco 3750X switches, 10 bridges, and 10 routers. What I'm doing is throughput testing. The problem is all of the routers have identical subnets because in the real world there won't be two of them in the same place. The 10 bridges were the easy part. I have one switch dedicated to LAN side and one dedicated to WAN side. Since the bridges themselves allow any traffic through because they are bridges I set all of the individual ports to essentially be their own subnet by making them L3 ports. Then, I set the switch to route the traffic based on subnet through the correct port using the ip route command in the CLI. I'm using a Spirent to generate traffic and the spirent lets me wrap traffic on different streams in different IP addresses. I made the uplink have a subnet of and I made every port have a subnet starting with being incremented by 1. This allowed me to send traffic from source address to destination address and vice versa by telling the switch to route any traffic with a subnet to port 1 (first device) and any traffic with a address to port 24 (uplink). The reason this works is because bridges don't care what the traffic is or where it is going so everybody is fine and happy.

Now I have to introduce 10 new devices that are all routers while maintaining the previous set up and I'm stumped. I've tried everything I can think of, different Vlans, trunking, routing, L3 ports, etc. If i try to isolate everything by Vlan they can't talk to each other. If i try to isolate everything by Vlan and trunk the uplink port it won't work because you need to do Vlan tagging and my device doesn't do that and I don't think the switch can do that for you. The routing doesn't work because the uplink port has to be it's own subnet and when that subnet tries to send traffic to the router it's considered foreign and gets dropped. With L3 ports you run in to the same problem, you can isolate all of the individual ports with their own subnet but the uplink port has to have a different subnet which automatically causes the router to drop the packets. The only configuration that works is a completely default dumb switch configuration and that is unacceptable because I need all of this traffic to be isolated because of the bridges. Without the isolation, all of the data will go through the nearest easy hop which will be one of the bridges, even if that isn't the right path the switch doesn't know any better. I can change the subnet on the routers but I can't deviate too far from the original subnet which is I tried setting up different subnets by incrementing the third octet by 1 every time,,,, etc. and think this setup will work I just don't know how to set the switch up. Setting up the switch to route the traffic properly without changing the subnet on any of the devices would be ideal.

Any help or ideas will be appreciated.




Re: Help with Isolating Traffic on Different Subnets

Have you tried SVI's ?

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