1-11
Software Configuration Guide For Cisco 2600 Series, Cisco 3600 Series, and Cisco 3700 Series Routers
OL-1957-03
Chapter 1
Understanding Interface Numbering and Cisco IOS Software Basics
Understanding Interface Numbering
Note
The slot number for all WIC interfaces is always 0. (The W0 and W1 slot designations are for
physical slot identification only.) Interfaces in the WICs are numbered from right to left, starting with
0/0 for each interface type, regardless of which physical slot the WICs are installed in. Some
examples are:
–
If physical slot W0 is empty and physical slot W1 contains a 1-port serial WIC, the interface in
the WIC is numbered Serial 0/0.
–
If slot W0 contains a 2-port serial WIC and slot W1 contains a 1-port serial WIC, the interfaces
in physical slot W0 are numbered Serial 0/0 and Serial 0/1, and the interface in physical slot W1
is numbered Serial 0/2.
–
If slot W0 contains a 2-port serial WIC and slot W1 contains a 1-port BRI WIC, the interfaces
in physical slot W0 are numbered Serial 0/0 and Serial 0/1, and the interface in physical slot W1
is numbered BRI 0/0.
Cisco 3745 Router Interface Numbering
The Cisco 3745 router chassis contains the following wide-area network (WAN) and local-area network
(LAN) interface types:
•
2 built-in FastEthernet LAN interfaces
•
3 slots in which you can install WAN or voice interface cards
•
4 network module slots.
Cisco 3745 Router Slot Numbering
The numbering format in the Cisco 3745 router is Interface type Slot number/Interface number. Two
examples are:
FastEthernet 0/0
Serial 1/2.
The slot numbers are as follows:
•
0 for all built-in interfaces
•
0 for all WIC interfaces
•
1 for the lower right network module slot
•
2 for the lower left network module slot
•
3 for the upper right network module slot
•
4 for the upper left network module slot
If double-wide network modules are installed, the slot numbers are as follows:
•
2 for the lower double-wide slot
•
4 for the upper double-wide slot
Interface (port) numbers begin at 0 for each interface type, and continue from right to left and (if
necessary) from bottom to top.