2960 Vlan ports for ISP media converter and Cisco 1841

[robert]

Hi,

Yesterday I had to connect a media converter (fiber to ethernet) to a Cisco 1841 router, but at the time I did not have a crossover rj45 cable, so I thought I just made 2 ports in a separate vlan on a 2960 switch to link them together, but I was unable to get traffic flow to ISP with the correct vlan number. The ISP expects to see vlan 490.

On the 1841 I have a sub interface encapsulating vlan as 490 and this is working, but as soon as I connected the links via vlan 490 ports on the switch - no traffic beyond the 1841. At the end I got hold on a rj45 crossover cable and connected the media converter directly to the 1841 and all was well.

But what was I doing wrong on the vlans ports on the switch? Tried multiply different configs without luck due to lack of knowledge - can anybody give a example on how 2 vlans ports on a switch should be configured to get this working?

Regards

Robert

[Reza Sharifi]

Hi,

Hard to tell without seeing your config, but if you have 2 vlans configured on the switch and then you are connecting the switch to the router (1841) you need to trunk that switch side with dot1q and also create 2 sub-interfaces on the router (one for each vlan) with dot1q encapsulation.

HTH