Cisco® serial and asynchronous modules provide highly flexible connections for Cisco 1800, 1900, 2800, 2900, 3800, and 3900 Series Integrated Services Routers (ISRs). These modules help customers enable applications such as WAN aggregation, transport of traditional protocols, console servers, and dial access servers. Customers can mix and match modules to tailor cost-effective solutions for common networking problems such as remote network management, external dial modem access, low-density WAN aggregation, transport of traditional protocols, and high-port-density support.
• Cisco 2800, 2900, 3800, and 3900 Series 4-Port Serial High-Speed WAN Interface Card (HWIC-4T): Four high-speed serial ports
• Cisco 1800, 1900, 2800, 2900, 3800, and 3900 Series 8-Port Asynchronous/Synchronous High-Speed WAN Interface Card (HWIC-8A/S-232): Eight low-speed asynchronous/synchronous ports, EIA-232 only
• Cisco 1800, 1900, 2800, 2900, 3800, and 3900 Series 8-Port Asynchronous High-Speed WAN Interface Card (HWIC-8A): Eight asynchronous EIA-232 ports
• Cisco 2800, 2900, 3800, and 3900 Series 16-Port Asynchronous High-Speed WAN Interface Card (HWIC-16A): Sixteen asynchronous EIA-232 ports
• Cisco 3900 Series 32-Port Asynchronous Service Module (SM-32A): Thirty-two asynchronous EIA-232 ports
• WAN links using Cisco High-Level Data Link Control (HDLC), Point-to-Point Protocol (PPP), or Frame Relay encapsulation: With up to eight synchronous serial ports, these HWICs are well suited for low-density WAN aggregation.
• Transport for traditional protocols: Synchronous serial ports can be used to connect to existing equipment using protocols such as IBM Systems Network Architecture (SNA), Synchronous Data Link Control (SDLC) Protocol, Binary Synchronous Communications (Bisync) Protocol, and X.25 Protocol. Cisco IOS® Software provides the capability to transport this traditional-protocol traffic through a TCP/IP network. This capability eliminates the need for expensive leased lines to support this traffic. With up to eight synchronous serial ports, these HWICs are well suited for low- and medium-density applications that provide transport for traditional protocols. For higher densities of synchronous ports, please see the NM-16A/S 16-port synchronous/asynchronous network module.
• Console servers and terminal servers: This solution allows Cisco ISRs to connect to the console or craft ports of other networking equipment to provide access to the console or craft ports from anywhere in the network. These modules are well suited for remote management of equipment in network installations. Cisco IOS Software provides a comprehensive set of security features to help ensure that only authorized personnel can access these ports.
• Dial access server: A Cisco ISR with asynchronous ports can connect to external modems to provide a dial access server. This capability provides low-density dial-in access to the network. For a dial access server solution with integrated modems, please see the 8-port and 16-port analog modem network modules.
Table 1. High-Density Synchronous/Asynchronous Cabling
Product Number |
Cable Type |
Length |
Connector Type |
CAB-HD4-232FC |
4-port EIA-232 DCE |
10 ft (3m) |
Socket DB-25 |
CAB-HD4-232MT |
4-port EIA-232 DTE |
10 ft (3m) |
Plug DB-25 |
Table 2. High-Density Asynchronous Cabling
• More ports in the HWIC form factor
• Capability to measure the incoming clock rate of synchronous ports in DTE mode (see the Cisco IOS Software show controller command)
• Higher synchronous speeds of up to 252 kbps on synchronous/asynchronous ports (HWIC-4A/S and HWIC-8A/S-232)
• Higher asynchronous speeds of up to 230.4 kbps
• Support for the lead manipulation feature
Ignoring Input Signals
Table 3. Lead Manipulation
Mode |
Required Input Leads |
Syntax to Ignore Input Leads |
DTE |
CTS, DCD, and DSR |
[no] ignore {cts | dcd | dsr} |
DCE |
RTS and DTR |
[no] ignore {dtr | local-loopback | rts} |
Viewing the State of Input Signals
• For serial interfaces configured for synchronous communication, enter the Cisco IOS Software show interface command.
• For serial interfaces configured for asynchronous communication, enter the Cisco IOS Software show line command.
Monitoring Input Signal Transition