vlan routing problem

[rchiera312]

Hello,

I am using packettracer, and am having a problem pinging past the first router with my workstations in the below topology.  I cannot ping f0/1 or anything past it on router BLUE or RED.  Configs are attached.

[MATTHIAS SCHAERER]

You have a conceptional issue in you network. You use the same subnets (192.168.100.0/24 amd 192.168.200.0/24) on both sides of your network. IP has a concept of contiguous network addressing so you are not allowed to separate the subnets by other subnets. Use adresses 192.168.101.0/24 and 192.168.201.0/24, configure them on router blue as well and you will be successful with your tests. (If you want to have the same addresses on both sides you'd need to configure bridging and you probably don't want that.)

Kind regards,

Mat

[rchiera312]

I see your idea, but this does not explain why i cannot ping the CORE router, right?

[Jon Marshall]

rchiera312 wrote:
I see your idea, but this does not explain why i cannot ping the CORE router, right?

Well it might because the red router and the blue router are both advertising 192.168.200.x to the core router. Do a "sh ip route" on the core router and see what it shows. It will probably show 2 routes to 192.168.200.x going different ways.

Jon

[MATTHIAS SCHAERER]

It is in fact as Jon says: you will end up seeing the route to 192.16.100.0/24 and 192.168.200.0/24 over both interfaces in the routing table of the CORE router. And as both routes have the same metric it's a matter of luck which route is taken by the algorithm. The router selects one or the other route based on destination addresses it tries to reach.

But to remember: your situation does not represent a reasonable network design so it is better to fix it than to have scientific discussions about it.

Kind regards,

Mat