Interface Naming Convention of Cisco Router

Interface Naming Convention of Cisco Router

If we install two serial interfaces in first slot of the modular router, that is slot0, and two Ethernet interfaces in the second slot of a modular router, that is slot1, and then the general naming convention could be as listed below

There are various interfaces on a router that helps data to travel from source system to destination system. Some of the interfaces are Serial interface, Ethernet, fast Ethernet, Token ring, Gigabit Ethernet etc. Different Ethernets have different speeds.

There are two kinds of routers

1.            Modular

2.            Non-Modular

Non-modular routers:  The non-modular routers have fixed number of interfaces. The naming convention of a non-modular Cisco router can be given as <Interface type><port number>.

Assume if there are 3 Ethernet interfaces and 2 serial interfaces on a router. All the interfaces are designated as listed below

a.            Ethernet0 or e0

b.            Ethernet1 or e1

c.             Ethernet2 or e2

d.            Serial0 or s0

e.            Serial1 or s1

The main disadvantage of non-modular routers is that we cannot expand the network as the interfaces are limited. In order to expand the network, we have to buy an additional router which increases the cost. To overcome this limitation Cisco came out with new concept call modular routers.

Modular routers: The modular routers as the name indicates these routers can be expanded. We can insert interface cards in the slots provided by the router to expand the networks without the necessity of buying a new router. This reduces the cost to a greater extent and eases the work of expansion.

The Cisco used the same naming convention as non-modular routers but the difference is that the slot number has also been added to the convention. Typical naming convention of a modular Cisco router can be given as <interface type><slot number/ port number>

Slot number indicates the number of slots that have been provided on the modular routers for expansion. Generally slot number starts from 0.  Cisco router 2600 has two slots of which the first slot is designated as slot 0 and the second slot is designated as slot 1.

If we install two serial interfaces in first slot of the modular router, that is slot0, and two Ethernet interfaces in the second slot of a modular router, that is slot1, and then the general naming convention could be as listed below

a.            Serial0/0 or s0/0

b.            Serial0/1 or s0/1

c.             Ethernet1/0 or e1/0

d.            Ethernet1/1 or e1/1

The two tired naming convention has certain limitations. Consider the same above example. If Ethernet cards are installed first on slot1, they are designated as Ethernet0/0 and Ethernet0/1.

On installing serial interface on slot0, the naming convention automatically changes as listed above. To overcome this issue, Cisco came out with three tire naming convention as  <interface type><slot number/ sub-slot number/ port number>.

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