Why Subinterfaces?

Can anyone be so kind to explain why are subinterfaces used exactly? I know how to configure it, i just don't get their purpose!

10x

Ps: Keep up the good work on this forum - i like!

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Fu Loser

Take a look at Frame Relay connection point-to-multipoint.

Subinterfaces simulate having multiple logical connections over a single phsical connection.

For instance a company has one T1 connection comming into Serial 0/1

In order to connect this branch to 7 other branch offices you create subinterfaces on Serial 0/1. This elminates the need to actually have 7 T1 lines comming into the office.

A subinterface is done by typing in INT SERIAL 0/1.x

x represents the subinterface number you wish to use as in .1 .2 .5 .200

Hope this helps I believe their is a TechNotes section that will explain this in detail. If not cisco.com will.

johnnynodough

Also used with Vlans for utilizing router on a stick with a fast ethernet port so you can route between mutiple vlans using one FA port.

kypumper

I thought the main reason for subinterfaces was too be able to still use split horizon.

Yankee

Yep KY, using point to point subinterfaces is a big advantage as they are each treated as individual connections from the same physical interface. What occurs on the ethernets is of no consequence to the serial configuration.

Yankee