Cisco Systems PA-POS-1OC3 Manual De Usuario

The default MTU size is 4470 bytes. The default value, 4470 bytes, exactly matches the maximum 
transmission unit (MTU) of the fiber distributed data interface (FDDI) and high-speed serial interface 
(HSSI) for autonomous switching.

To set the MTU size, enter the mtu bytes command, where bytes is a value in the range of 64 to 117994.

Router(config)# interface pos 3/0

Router(config-if)# mtu

To restore the default of 4470 bytes, enter the no mtu command.

Router(config)# interface pos 3/0

Router(config-if)# no mtu

The default framing setting is SONET STS-3c. 

To configure for SDH STM-1, enter the pos framing sdh command:

Router(config)# interface

Router(config-if)# pos framing sdh

To change back to SONET STS-3c, enter the no pos framing sdh command.

Router(config)# interface

Router(config-if)# no pos framing sdh

The clocking default specifies that the PA-POS-1OC3 use the recovered receive (RX) clock to provide 
transmit (TX) clocking (called loop timing). 

If line loopback is selected, the PA-POS-1OC3 is forced into loop timing mode until the loopback is 
disengaged.

To specify that the PA-POS-1OC3 generate the transmit clock internally, enter the clock source internal 
command:

Router(config)# interface

Router(config-if)# clock source internal