Cisco 3850 connect to Cisco 1900 Internet router

peterv · ‎09-19-2014

I am having a strange problem that I have not yet been able to resolve, I have done a fair bit of testing before posting this as it may get me a faster solution.

Currently I have a 3750 Switch with a number of Vlans, one of the Vlan's has a Cisco 1900 ISP feed router attached and all working fine, Routing via this switch is all working as expected.

Here's the problem.

I am replacing the 3750 with a 3850 stack and copy most of the configuration across, I say most as a few commands are no longer supported on the 3850.

I connect the Cisco 1900 ISP feed router as I had previously however now the Internet does no longer work, everything else is fine, from my client Vlan I can still ping the Vlan Interface the Cisco 1900 is connected to but I cannot ping the router from a client Vlan.

I can ping the Cisco 1900 router from the Cisco 3850 switch and I can ping the Internet from the 3850 Switch through the Cisco 1900.

If I connect a laptop to the same Vlan as the Cisco 1900 router and give it for example the IP address of the router I can ping the Laptop from the client Vlan suggesting to me there is no routing problem, however when I re-connect the Cisco 1900 I cannot ping it even though it's the same IP.

The router is pingable as I can ping it from the 3850 switch.

If I connect a laptop to the same Vlan as the Cisco 1900 and give it an IP in the same range and specify the router as my default gateway I can connect to the Internet.

From my client Vlan I can ping the Laptop but not the Cisco 1900 router.

What's going on, am I loosing it or is there a subtle command that I need to type on the Cisco 3850 to make this work.

Any suggestion however small as I'm currently going round in circles.

Thanks in advance.

Reza Sharifi · ‎09-19-2014

Did you turn on "ip routing" on the 3850?

HTH

peterv · ‎09-19-2014

Thanks for your comment.

I have indeed, when I replace the Cisco router with a laptop and give it the same IP I CAN ping it.

Martin Carr · ‎09-20-2014

Have you configured a default route, as this will be needed?

As to the issue I assume you have added or changed addresses, as it seems the 1900 does not have a route to the 'client' VLAN, hence why the laptop works.

As a tip, ping using a source address.

Martin

peterv · ‎09-21-2014

Thanks all for your suggestions.

I managed to have a look at the Internet feed router configuration and noticed it had some EIGRP settings.

My L3 switch did not have the EIGRP protocol enabled until I licensed IPservices.

Added the required EIGRP configuration details and hey presto.

thanks again for your suggestions.