Chapter 8 Configuring the Serial Interface
Information About Configuring Serial Interfaces
Information About Configuring Serial Interfaces
To configure serial interfaces, you must understand the following concept:
•Cisco HDLC Encapsulation, page
•PPP Encapsulation, page
•Keepalive Timer, page
•Frame Relay Encapsulation, page
Cisco HDLC Encapsulation
Cisco
Note Cisco HDLC is the default encapsulation type for the serial interfaces.
When the encapsulation on a serial interface is changed from HDLC to any other encapsulation type, the configured serial subinterfaces on the main interface inherit the newly changed encapsulation and they do not get deleted.
Cisco HDLC uses keepalives to monitor the link state, as described in the “Keepalive Timer” section on page
PPPEncapsulation
PPPis a standard protocol used to send data over synchronous serial links. PPP also provides a Link Control Protocol (LCP) for negotiating properties of the link. LCP uses echo requests and responses to monitor the continuing availability of the link.
Note When an interface is configured with PPP encapsulation, a link is declared down and full LCP negotiation is
PPPprovides the following Network Control Protocols (NCPs) for negotiating properties of data protocols that will run on the link:
•IP Control Protocol (IPCP) to negotiate IP properties
•Multiprotocol Label Switching control processor (MPLSCP) to negotiate MPLS properties
•Cisco Discovery Protocol control processor (CDPCP) to negotiate CDP properties
•IPv6CP to negotiate IP Version 6 (IPv6) properties
•Open Systems Interconnection control processor (OSICP) to negotiate OSI properties
Cisco 819 Series Integrated Services Routers Software Configuration Guide
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