Hi Milan,

If you want this trunk to remain a layer2 trunk, you can use the vlan interfaces belonging to the vlans allowed on this trunk to route traffic.

E.g. your trunk carries vlans 2 and 3, then you can configure the vlan interfaces like this:

interface vlan 2

ip address x.x.x.x x.x.x.x

interface vlan 3

ip address y.y.y.y y.y.y.y

Then you can use the ip addresses of these interfaces in your ospf configuration with the "network" ospf router command.

If you provide more info about your current and expected configurations, then I can give you a more specific answer.

Cheers:

Istvan