
C613-50186-01 Rev B
Command Reference for AR2050V
593
AlliedWare Plus™ Operating System - Version 5.4.7-1.x
PPP C
OMMANDS
MTU
(PPP)
mtu (PPP)
Overview
Use this command to set the Maximum Transmission Unit (MTU) size for a PPP
interface, where MTU is the maximum packet size that PPP interfaces can transmit.
Use the
no
variant of this command to remove a previously specified MTU size for
a PPP interface, and restore the default MTU size (1492 bytes) for PPP interfaces.
Syntax
mtu <
mtu-size
>
no mtu
NOTE
:
For PPPoE the minimum MTU value is 128.
Default
The default MTU size is 1492 bytes for PPPoE interfaces. The MTU should be greater
than, or equal to, the MSS.
Mode
Interface Configuration for PPP interfaces.
Usage
If a router receives an IPv4 packet for another PPP interface with an MTU size
smaller than the packet size, and if the packet has the ‘
don’t fragment
’ bit set,
then the switch will send an ICMP ‘
destination unreachable
’ (3) packet type and
a ‘
fragmentation needed and DF set
’ (4) code back to the source.
command to set the Maximum Segment Size (MSS) after
first setting the MTU size.
Examples
To configure an MTU size of 1492 bytes on PPP interface ppp0, use the commands:
awplus#
configure terminal
awplus(config)#
interface ppp0
awplus(config-if)#
mtu 1492
To restore the MTU size to the default MTU size of 1492 bytes on PPP interface
ppp0
, use the commands
awplus#
configure terminal
awplus(config)#
interface ppp0
awplus(config-if)#
no mtu
Related
Commands
Parameter
Description
<
mtu-size
>
<68-1492> Specifies the Maximum Transmission Unit (MTU) size in
bytes, where 1492 bytes is the default MTU size for a PPPoE interface
and 1500 bytes for PPP via other lower layer interface types. This
allows for the 8-byte PPPoE header that is added to make up the total
of a 1582 byte packet that matches the default MTU size for the
Ethernet link..