Cisco XR 12000 Specifications download pdf (Page 74)

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Cisco XR 12000 Series Router SIP and SPA Software Configuration Guide, Release 3.2

Release 3.2, OL-6396-01, Rev.A1 January 9, 2006

Chapter 6 Configuring POS SPAs on Cisco IOS XR Software

Configuration Tasks

Configuring a POS Interface

This task explains how to create a basic POS configuration. There are many other possible parameters

that can be set. Only the most basic are illustrated. Not all configuration steps are required.

Default Settings for POS Interface Configurations

When an interface is enabled on a POS SPA and its associated SIP with no additional configuration

commands applied, the default interface settings shown in Table 6-1 are present. These default settings

can be changed by configuration. Default settings do not appear in the output of the show

running-config command.

Keepalive Timer

The high-level data-link control (HDLC) usage of the keepalive timer also applies to PPP encapsulation

to control how often echo request (ECHOREQ) packets are sent out.

Use the keepalive command in interface configuration mode to set how frequently Link Control Protocol

(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 commands. For both PPP and HDLC, a keepalive of 0 disables

keepalives and is reported in the show running-config command 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.

Keepalives are independent between the two peers. One peer end can have keepalives enabled, the other

end can have them disabled. Even if keepalives are disabled locally, LCP will still respond with

ECHOREP packets to the ECHOREQ packets it receives. Similarly, it will also work if the period of

keepalives at each end is different.

When the interface has PPP encapsulation, if LCP sends three ECHOREQ packets without an

ECHOREP being received then it declares the link down and initiates full LCP negotiation again. If the

interface has HDLC encapsulation, the number of resends is only three before the link is taken down.

Only when LCP negotiation is complete (for example, when LCP is open) are ECHOREQ packets sent

out.

Table 6-1 POS SPA and SIP Default Interface Settings

Parameter Configuration File Entry Default Settings

Keepalive keepalive [disable]

no keepalive [disable]

keepalive 10 seconds

Encapsulation encapsulation [hdlc | ppp] hdlc

Maximum Transmission Unit

(MTU)

mtu bytes 4474 bytes

Cyclic Redundancy Check

(CRC)

crc [16 | 32] 32

1 2 ... 69 70 71 72 73 74 75 76 77 78 79 ... 135 136

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