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This chapter describes how to connect serial network modules for Cisco modular routers. It contains the following sections:
Serial connections can be provided by either WAN interface cards or network modules. For more information about WAN interface cards, see the Cisco WAN Interface Cards Hardware Installation Guide. To obtain this publication, see the "Obtaining Documentation" section.
Before you connect a device to a serial port, you need to know the following:
A device that communicates over a synchronous serial interface is either a DTE or a DCE device. A DCE device provides a clock signal that times communications between the device and the router. A DTE device does not provide a clock signal. DTE devices usually connect to DCE devices. The documentation that accompanied the device should tell you whether it is DTE or DCE. (Some devices have a jumper to select DTE or DCE mode.) If you cannot find this information in your documentation, see Table 6-1 to help you determine the proper device type.
| Device Type | Typical Connector | Typical Devices |
|---|---|---|
DTE | Male1 | Terminal PC |
DCE | Female2 | Modem CSU/DSU Multiplexer |
| 1If pins protrude from the base of the connector, the connector is male. 2If the connector has holes to accept pins, the connector is female. |
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Note Serial ports configured as DTE require external clocking from a CSU/DSU or other DCE device. |
Cisco Systems offers five types of serial cables (also called serial adapter cables or transition cables):
The documentation for the device you plan to connect to the serial port should indicate which interface it uses. You can then order a serial transition cable of the correct type.
All serial cables provide a universal 60-pin plug at the network module or WAN interface card end. The network end of each cable provides the physical connectors most commonly used for the interface. For example, the network end of the EIA/TIA-232 serial cable is a DB-25 connector, the most widely used EIA/TIA-232 connector.
All serial interface types except EIA-530 are available in DTE or DCE format: DTE with a plug connector at the network end and DCE with a receptacle at the network end. V.35 is available in either mode with either gender at the network end. EIA-530 is available in DTE only.
Serial cables are not provided with the network module. For ordering information, see the "Obtaining Technical Assistance" section.
Although manufacturing your own serial cables is not recommended (because of the small size of the pins on the DB-60 serial connector), cable pinouts are provided in the online document Cisco Modular Access Router Cable Specifications. This document is located on the Documentation CD-ROM that accompanied your router, and on Cisco Connection Online. For further information, see the "Obtaining Documentation" section.
All serial signals are subject to distance limits, beyond which the signal degrades significantly or is completely lost. Generally, the slower the data rate, the greater the distance.
Table 6-2 lists recommended maximum speeds and distances for each serial interface type. If you understand and compensate for potential electrical problems, you may get good results at speeds and distances greater than those listed. For instance, the recommended maximum rate for V.35 is 2 Mbps, but 4 Mbps is commonly used.
| EIA/TIA-232 Distance | EIA/TIA-449, V.35, X.21, EIA-530 Distance | |||
|---|---|---|---|---|
| Rate (bps) | Feet | Meters | Feet | Meters |
2400 | 200 | 60 | 4100 | 1250 |
4800 | 100 | 30 | 2050 | 625 |
9600 | 50 | 15 | 1025 | 312 |
19200 | 25 | 8 | 500 | 150 |
38400 | 12 | 4 | 250 | 75 |
56000 | 9 | 3 | 100 | 30 |
1544000 (T1) | - | - | 50 | 15 |
Balanced drivers allow EIA/TIA-449 signals to travel greater distances than EIA/TIA-232 signals. The recommended distance limits for EIA/TIA-449 shown in Table 6-2 are also valid for V.35, X.21, and EIA-530. Typically, EIA/TIA-449 and EIA-530 support 2-Mbps rates, and V.35 can support 4-Mbps rates.
The following data-rate limitations apply to the slow-speed serial interfaces found on asynchronous/synchronous serial modules:
An asynchronous network module provides two or four 60-pin receptacles. Each receptacle connects to asynchronous devices by means of an octal cable that provides a 60-pin plug at the module end and eight connectors at the network end, one for each of the eight EIA/TIA-232 serial ports. Depending on the type of cable, the network end consists of either RJ-45 plugs or male DB-25 connectors. RJ-45-to-DB-25 adapters are also available.
Ports are numbered from right to left and from bottom to top, as labeled on the module's rear panel. (See the "Asynchronous Network Module Interface Numbering" section.)
Octal cables are not provided with the network module. For ordering information, see the "Obtaining Technical Assistance" section.
Use an octal cable, and adapters if necessary, to connect each of the module's 60-pin receptacles to one or more asynchronous modems, terminals, or other devices. (See Figure 6-1.)
Certain 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 asynchronous network module is related to the slot number where the module is installed and the unit number of the port in the module.
Cisco 3600 series slot numbering is explained in the "Cisco 3600 Series Interface Numbering" section.
Ports on the 16-port and 32-port asynchronous network modules correspond to the outputs of the octal cables that connect the module to the network. These ports 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 32-port module) from bottom to top. In the 16-port module, the right connector provides ports 0 to 7, and the left connector provides ports 8 to 15, as labeled on the module's rear panel. In the 32-port module, the connectors in the bottom row provide ports 0 to 7 and 8 to 15, and the connectors in the top row provide ports 16 to 23 and 24 to 31.
The interface number of a port is determined using the following relation:
interface-number = (32 x slot-number) + unit-number + 1
For example, asynchronous 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 a 16-port asynchronous module, a 32-port asynchronous module, or some other type of module entirely, or even whether there is a network module in slot 0 at all. If you move the module in slot 1 to a different slot, however, its interface numbers change.
Table 6-3 shows the range of interface numbers available for each type of asynchronous network module in each Cisco 3600 series router slot. (Interface 0 is automatically assigned to the console.)
| Slot Number | Interface Numbers (16-Port Module) | Interface Numbers (32-Port Module) |
|---|---|---|
0 | 1-16 | 1-32 |
1 | 33-48 | 33-64 |
2 | 65-80 | 65-96 |
3 | 97-112 | 97-128 |
4 | 129-144 | 129-160 |
5 | 161-176 | 161-192 |
6 | 193-208 | 193-224 |
Interface numbering for Cisco 2600 series routers differs from Cisco 3600 series interface numbering in the following ways:
The 4-port and 8-port asynchronous/synchronous network modules, when configured for asynchronous operation under Cisco IOS releases prior to 11.2(7)P, use a different interface numbering algorithm:
interface-number = (16 x slot-number) + unit-number + 1
Table 6-4 shows the numbers available under this numbering scheme. These interface numbers create potential conflicts with the numbers assigned to 16-port and 32-port asynchronous modules: it would be possible for a 16-port or 32-port asynchronous module in one slot to overlap the interface numbers of a 4-port or 8-port asynchronous/synchronous module in another slot.
| Slot Number | Interface Numbers (4-Port Module) | Interface Numbers (8-Port Module) |
|---|---|---|
0 | 1-4 | 1-8 |
1 | 17-20 | 17-24 |
21 | 33-36 | 33-40 |
31 | 49-52 | 49-56 |
| 1Cisco 3640 and Cisco 3660 routers only. |
To prevent this conflict, Cisco IOS Release 11.2(7)P, which is required to operate 16-port and 32-port asynchronous network modules, checks when it boots for the presence of 4-port and 8-port asynchronous/synchronous network modules configured as asynchronous. If if finds any, it rewrites the starting configuration in nonvolatile random access memory (NVRAM), if necessary, to adopt the new line numbering scheme for these modules, as shown in Table 6-5.
| Slot Number | Interface Numbers (4-Port Module) | Interface Numbers (8-Port Module) |
|---|---|---|
0 | 1-4 | 1-8 |
1 | 33-36 | 33-40 |
21 | 65-68 | 65-72 |
31 | 97-100 | 97-104 |
| 1Cisco 3640 and Cisco 3660 routers only. |
When an automatic configuration update is performed, the following message appears:
Line number convention changed from 16 lines/slot to 32 lines/slot.
This section provides information about the 4-port serial network module (Cisco product number NM-4T). (See Figure 6-2.) With the appropriate serial transition cable, each port on this module can provide an EIA/TIA-232, EIA/TIA-449, V.35, X.21, EIA-530 DTE, or nonreturn to zero/nonreturn to zero inverted (NRZ/NRZI) serial interface. The module provides a synchronous data rate of 8 MB/sec on port 0, 4 MB/sec each on port 0 and port 2, or 2 MB on all four ports simultaneously.
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Note Half-duplex and binary-synchronous communications are not supported on the 4-port serial network module. |
The 4-port serial network module provides four universal high-density 60-pin receptacles. The serial cable attached to each receptacle determines the port's electrical interface type and mode, DTE or DCE.
After you install a 4-port serial module, use the appropriate serial cable to connect each of the module's DB-60 serial ports to a synchronous modem, channel service unit/data service unit (CSU/DSU), or other DCE equipment. (See Figure 6-3.)
All network modules have an enable (EN) LED. This LED indicates that the module has passed its self-tests and is available to the router.
Each port on the 4-port serial network module also has the additional LEDs shown in Figure 6-4 and described in Table 6-6.
| LED | Meaning |
|---|---|
CN/LP | Connect when green, loopback when yellow |
RXC | Receive clock |
RXD | Receive activity |
TXC | Transmit clock |
TXD | Transmit activity |
This section provides information about the following network modules:
When used with corresponding octal cables, these modules provide 16 or 32 EIA/TIA-232 data terminal equipment (DTE) serial interfaces. Speeds up to 134.4 kbps are supported.
All network modules have an enable (EN) LED. This LED indicates that the module has passed its self-tests and is available to the router.
Each port on an asynchronous network module also has a green status LED to indicate that the port is connected to the network. These LEDs are grouped in blocks of eight to the left of each module, and labeled with the port numbers. (See Figure 6-7 and Figure 6-8.)
This section provides information about the following network modules for Cisco modular routers:
With the appropriate serial transition cable, the ports on these modules can provide an EIA/TIA-232, EIA/TIA-449, V.35, X.21, EIA-530 DTE, or NRZ/NRZI serial interface.
Figure 6-11 shows LEDs for the 4-port asynchronous/synchronous serial network module. Figure 6-12 shows LEDs for the 8-port asynchronous/synchronous serial network module.
All network modules have an enable (EN) LED. This LED indicates that the module has passed its self-tests and is available to the router.
Each port on an asynchronous/synchronous serial network module also has the additional LEDs shown in Table 6-7.
| LED | Meaning |
|---|---|
CN/LP | Connect when green, loopback when yellow |
RXC | Receive clock |
RXD | Receive activity |
TXC | Transmit clock |
TXD | Transmit activity |
Posted: Fri Jun 2 16:59:36 PDT 2000
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