Subinterface ?

Manglian

Hi everyone

Just curious , For example we have a one main site (HeadOffice HO) and two brances. we are connecting two branches to Head Office use WAN technologing Frame Relay. When we have physical interfaces available on Head Office router, why we use only one physical interface and will use subinterface of of it . Suppose we have serial interface serial s0/1 why not we use other physical serial interfaces if available like s0/2 we use subinterface which 0/1.1 and 0/1.2.

Is cost saving?
because one LMI ( physical connection between Router DTE and Frame Relay Switch DCE) can have serveral DLCIs ?

Answere are requested please

cheers

chimera82

I think if your have multiple physical serial interfaces, use them. The reason you'd use subinterfaces is because of split horizon where you wouldn't be able to broadcast out routing updates from R2 to R3. If you had multiple serial interfaces, I don't think that would be an issue. Also it would be easier to manage growth by just adding another subinterface.

Slowhand

It's very possible that your company is only using the one physical interface to make sure they have the other in case they need to add more connections but don't run low on bandwidth. You know, keeping a spare for future use.

bighornsheep

There could be a few reasons why, I'm thinking it's likely due to the cost of your FR circuit. Your company is probably paying for a basic point-to-multipoint cloud.