Cisco Systems 8510 CSR, 8540 CSR appendix Customizing the Configuration, Additional Configurations

Chapter 4 Configuring Interfaces

Configuring the POS OC-12c Uplink Interface (Catalyst 8540)

Additional Configurations

To configure additional properties to match those of the interface at the far end, perform the following steps, beginning in global configuration mode:

	Command	Purpose
Step 1
	Router(config-if)# no keepalive	Turns off keepalive messages. Keepalive messages, though not
		required, are recommended.
Step 2
	Router(config-if)# no cdp enable	Turns off CDP, which is not required.
Step 3
	Router(config-if)# crc {16 32}	Sets the CRC value. If the device to which the POS module is
		connected does not support the default CRC value of 32, set both
		devices to use a value of 16.
Note	The above steps apply both to the POS OC-12c uplink interface on the switch router and
	to the interface to which it connects at the far end.

Customizing the Configuration

This section describe how to customize the configuration of the POS OC-12c uplink interface to match your network environment.

Setting the MTU Size

To set the maximum transmission unit (MTU), perform the following steps, beginning in global configuration mode:

	Command	Purpose
Step 1
	Router(config)# interface pos	Enters interface configuration mode and specifies the POS
	slot/subslot/interface	interface to configure.
	Router(config-if)#
Step 2
	Router(config-if)# mtu bytes	Configures the MTU size up to a maximum of 9188 bytes. Default
		MTU size is 4470 bytes.
Note	The POS OC-12c uplink interface supports IP unicast and IP multicast fragmentation. For
	IP unicast fragmentation, the packet must ingress on a POS interface and egress on any
	interface. For IP multicast fragmentation, IP multicast data packets greater than
	1500 bytes are fragmented to 1500 bytes on the ingress POS interface before being
	switched to other members in the multicast group. All the members in the multicast group
	must have a MTU equal to or greater than 1500 bytes.

	Layer 3 Switching Software Feature and Configuration Guide
78-6235-04, Cisco IOS Release 12.0(10)W5(18)		4-17