Specifications

mtu
MP-361
Cisco IOS Multiprotocol Label Switching Command Reference
January 2010
– Dot1Q header—4 bytes
– CRC—4 bytes
• If you are using MPLS, be sure that the mpls mtu command is configured for a value less than or
equal to the interface MTU.
• If you are using MPLS labels, then you should increase the default interface MTU size to
accommodate the number of MPLS labels. Each MPLS label adds 4 bytes of overhead to a packet.
Note For the Gigabit Ethernet SPAs on the Cisco uBR10012 router, the default MTU size is 1500 bytes. When
the interface is being used as a Layer 2 port, the maximum configurable MTU is 9000 bytes. The SPA
automatically adds an additional 22 bytes to the configured MTU size to accommodate some of the
additional overhead.
Examples The following example specifies an MTU of 1000 bytes:
Router(config)# interface serial 1
Router(config-if)# mtu 1000
Cisco uBR10012 Universal Broadband Router
The following example shows how to specify an MTU size on a Gigabit Ethernet SPA on the
Cisco uBR10012 router:
Router# configure terminal
Router(config)# interface GigabitEthernet3/0/0
Router(config-if)# mtu 1800
Related Commands Command Description
encapsulation smds Enables SMDS service on the desired interface.
ip mtu Sets the MTU size of IP packets sent on an interface.