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Cisco 3700 Series Routers Hardware Installation Guide
OL-2180-08
Chapter 1 Overview of Cisco 3700 Series Routers
Interface Numbering
Interface Numbering
This section describes numbering conventions for interfaces on Cisco 3725 and Cisco 3745 routers.
Cisco 3725 Interfaces
Each individual interface (port) on a Cisco 3725 router is identified by number, as described in the
following sections.
WAN and LAN Interface Numbering
The Cisco 3725 router chassis contains the following WAN and LAN interface types:
• Two built-in Fast Ethernet LAN interfaces
• Three slots in which you can install WAN interface cards (WICs)
• One single-wide slot (slot 1) in which you can install one network module
• One double-wide slot (slot 2) in which you can install one single-wide or double-wide network
module
The numbering format 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 interfaces in the single-wide network module slot
• 2 for interfaces in the double-wide network module slot
Interface (port) numbers begin at 0 for each interface type, and continue from right to left and (if
necessary) from bottom to top.
Figure 1-3 shows an example of interface numbering on a Cisco 3725 router with these interfaces:
• A WIC in each WIC slot (containing interfaces Serial 0/0 and Serial 0/1 in physical slot W0,
interface Serial 0/2 in physical slot W1, and interface BRI 0/0 in physical slot W2)
• A 2-port T1 network module in slot 1 (containing the following ports: T1 1/0 and T1 1/1)
• A 36-port EtherSwitch network module in slot 2 (containing the following ports: Fast Ethernet 2/0
through 2/35, and Gigabit Ethernet 2/0 and 2/1)
• Two built-in Ethernet 10/100-Mbps interfaces—Fast Ethernet 0/0 and Fast Ethernet 0/1