Interface Numbering
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Interface Numbering
Cisco IOS software identifies each modem uniquely by its slot number and port number.
Some Cisco IOS configuration commands identify asynchronous ports by an interface number (or a line
number, which is the same as the interface number). The interface number of a port on an 8- or 16-port
analog modem network module is related to the slot number where the module is installed and the
number of the port in the module.
Ports in the 8- and 16-port analog modem network modules are numbered in the same pattern as slot
numbers, beginning at 0 at the lower right and continuing from right to left and (in the 16-port module)
from bottom to top.
The interface number of a port is determined in the following way:
interface-number = (32 x slot-number) + port-number + 1
For example, modem port 12 in slot 1 corresponds to interface number (32 x 1) + 12 + 1 = 45. This is
also the line number for the port. Port 12 in slot 1 is always assigned interface number 45, regardless of
whether the module in slot 0 is an 8-port analog modem network module, a 16-port analog modem
module, or some other kind of module entirely, or even whether there is a network module in slot 0 at
all. If you move the module from slot 1 to a different slot, however, its interface numbers change.
Table 10-1
module in each router slot. (Interface 0 is automatically assigned to the console.)
Table 10-1 16- and 32-Port Analog Module Interface Numbering
Slot Number
0
1
Cisco Network Modules Hardware Installation Guide
10-4
ITU-T V.23 at 75 and 1200 bps
–
ITU-T V.21 at 300 bps
–
–
BELL 103 and 212a
Standardized fax protocols
ITU-T V.17
–
ITU-T V.29
–
ITU-T V.27ter
–
ITU-T V.21 channel 2
–
EIA 578 Class 2
–
Group 3 fax class 1 and class 2
–
Standardized modem error correction and compression
–
MNP 2 – 4
ITU-T V.42 Link Access Procedure for Modems ( LAPM)
–
Microcom Network Protocol (MNP) 5
–
V.42bis (with 4-K dictionaries)
–
ITU-T V.44
–
shows the range of interface numbers available for each type of analog modem network
Interface Numbers (8-Port Module)
1–8
33–40
Chapter 10
Connecting Analog Modem Network Modules
Interface Numbers (16-Port Module)
1–16
33–48
OL-2485-20