Alcatel-Lucent 7750 Configuration Manual page 365

Service router

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largest physical packet the port can transmit or the far-end Ethernet port can receive. Packets received larger

than the MTU will be discarded. Packets that cannot be fragmented at egress and exceed the MTU are dis-

The value specified for the MTU includes the destination MAC address, source MAC address, the Ethertype

or Length field and the complete Ethernet payload. The MTU value does not include the preamble, start of

frame delimiter or the trailing CRC.

PoS channels use the MTU to define the largest PPP payload a PoS frame may contain. A significant differ-

ence between SONET/SDH PoS channel and Ethernet physical MTU values the overhead considered part of

the framing method and the overhead considered to be part of the application using the frame. In Ethernet,

the preamble, start of frame delimiter and the CRC are considered part of the framing overhead and not part

of the frame payload. For a PoS channel, the HDLC framing overhead is not included in the physical MTU;

only the PPP and PPP payload are included. If the port mode or encapsulation type is changed, the MTU

assumes the default values of the new mode or encapsulation type.

The no form of this command restores the default values.

The default MTU value depends on the (sub-)port type, mode and encapsulation and are listed in the follow-

10/100, Gig, or 10GigE

SONET/SDH or TDM

ATM, SONET/SDH or TDM

10/100 or 100FX Ethernet

mtu-bytes — Sets the maximum allowable size of the MTU, expressed as an integer.

7750 SR Interface Configuration Guide

512 — 9212config>port>sonet-sdh>path512 — 9208

config>port>tdm>ds3

config>port>tdm>ds1>channel-group512 — 9208

Interface Configuration

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