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Parameters
ieee-address — Specifies the 48-bit MAC address in the form aa:bb:cc:dd:ee:ff or aa-bb-cc-dd-ee-ff where
aa, bb, cc, dd, ee and ff are hexadecimal numbers. Allowed values are any non-broadcast, non-multicast
MAC and non-IEEE reserved MAC addresses.
mtu
Syntax
mtu mtu-bytes
no mtu
Context
config>port>ethernet
config>port>sonet-sdh>path
config>port>tdm>ds1>channel-group
config>port>tdm>ds3
config>port>tdm>e1>channel-group
config>port>tdm>e3
Description
This command configures the maximum payload MTU size for an Ethernet port or PPP-enabled port or sub-
port and Frame Relay-enabled port or subport. The Ethernet port level MTU parameter indirectly defines the
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
discarded.
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
difference 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.
Default
The default MTU value depends on the (sub-)port type, mode and encapsulation and are listed in the
following table:
10/100 or Gig
10/100 or Gig
10/100 or Gig
SONET/SDH or TDM
SONET/SDH or TDM
7710 SR OS Interface Configuration Guide
Type
Access
Access
Access
Access
Access
Mode
Encap Type
null
dot1q
q-in-q
mpls
bcp-null
Interface Configuration
Default
(Bytes)
1514
1518
1522
1506
1518
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