Alcatel-Lucent 7750 - MTU Configuration Guidelines; Table 27: MTU Default Values

Interface Configuration
7750 SR Interface Configuration Guide Page 169
MTU Configuration Guidelines
Observe the following general rules when planning your service and physical MTU
configurations:
• The 7750 SR must contend with MTU limitations at many service points. The physical
(access and network) port, service, and SDP MTU values must be individually defined.
• Identify the ports that will be designated as network ports intended to carry service traffic.
• MTU values should not be modified frequently.
• MTU values must conform to both of the following conditions:
→ The service MTU must be less than or equal to the SDP path MTU.
→ The service MTU must be less than or equal to the access port (SAP) MTU.
Default MTU Values
Table 27 displays the default MTU values which are dependent upon the (sub-) port type, mode,
and encapsulation.
*The default MTU for Ethernet ports other than Fast Ethernet is actually the lesser of 9212 and
any MTU limitations imposed by hardware which is typically 16K.
Table 27: MTU Default Values
Port Type Mode Encap Type Default
(bytes)
Ethernet access null 1514
Ethernet access dot1q 1518
Fast Ethernet network — 1514
Other Ethernet network — 9212*
SONET path or TDM channel access BCP-null 1518
SONET path or TDM channel access BCP-Dot1q 1522
SONET path or TDM channel access IPCP 1502
SONET path or TDM channel network — 9208
SONET path or TDM channel access frame-relay 1578
SONET path or TDM channel access atm 1524