Cisco Systems XR 12000 SIP-501 Cisco IOS XR PPP Encapsulation, Cisco IOS XR Hdlc Encapsulation

Configuring Serial Interfaces on Cisco IOS XR Software

Information About Serial Interfaces

•t1-num: T1 or E1 channel number. T1 channels range from 0 to 23; E1 channels range from 0 to 30.

•channel-group-number: Time slot number. T1 time slots range from 1 to 24; E1 time slots range from 1 to 31. The channel-group-numberis preceded by a colon and not a slash.

Use the question mark (?) online help function following the serial keyword to view a list of all valid interface choices.

Cisco IOS XR PPP Encapsulation

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.

PPPprovides 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

Note The default encapsulation type for the serial line card configurations is Cisco HDLC. To change the encapsulation type to be PPP, you must use the encapsulation ppp command in interface configuration mode for the serial interface.

Cisco IOS XR HDLC Encapsulation

Cisco High-Level Data Link Controller (HDLC) is Cisco’s proprietary protocol for sending data over synchronous serial links using HDLC. Cisco HDLC also provides a simple control protocol called Serial Line Address Resolution Protocol (SLARP) to maintain serial link keepalives. HDLC is the default encapsulation for serial interfaces under Cisco IOS XR software.

Keepalive Timer

The HDLC usage of the keepalive timer also applies to PPP encapsulation to control how often ECHOREQ (echo request) packets are sent out.

Use the keepalive command in interface configuration mode to set how frequently LCP should send out ECHOREQ packets to its peer. To restore the system to the default keepalive interval of 10 seconds, use the keepalive command with no argument. To disable keepalives, use the no keepalive or keepalive disable command. For both PPP and Cisco HDLC, a keepalive of 0 disables keepalives and is reported in the show running-configcommand output as keepalive disable.

When LCP is running on the peer and receives an ECHOREQ packet, it should respond with an echo reply (ECHOREP) packet, regardless of whether keepalives are enabled on the peer.

Cisco IOS XR Interface and Hardware Component Configuration Guide

HC-120