
C613-50186-01 Rev B
Command Reference for AR2050V
377
AlliedWare Plus™ Operating System - Version 5.4.7-1.x
I
NTERFACE
C
OMMANDS
MTU
mtu
Overview
Use this command to set the Maximum Transmission Unit (MTU) size for VLANs,
where MTU is the maximum packet size that VLANs can transmit. The MTU size
setting is applied to both IPv4 and IPv6 packet transmission.
Use the
no
variant of this command to remove a previously specified Maximum
Transmission Unit (MTU) size for VLANs, and restore the default MTU size (1500
bytes) for VLANs.
Syntax
mtu <
68-1582
>
no mtu
Default
The default MTU size is 1500 bytes for VLAN interfaces.
Mode
Interface Configuration for VLAN interfaces.
Usage
If a device receives an IPv4 packet for Layer 3 switching to another VLAN with an
MTU size smaller than the packet size, and if the packet has the ‘
don’t fragment
’
bit set, then the device will send an ICMP ‘
destination unreachable
’ (3) packet
type and a ‘
fragmentation needed and DF set
’ (4) code back to the source. For
IPv6 packets bigger than the MTU size of the transmitting VLAN interface, an ICMP
‘
packet too big
’ (ICMP type 2 code 0) message is sent to the source.
Note that you cannot configure MTU on bridge interfaces. The MTU of the bridge
interface is determined by the member interface of the bridge which has the
lowest MTU. For example, if you attach eth1 with MTU 1200, ppp1 with MTU 1400,
and vlan1 with MTU 1500 to a bridge interface, the MTU for that interface will be
1200.
output will only show MTU size for VLAN interfaces.
Examples
To configure an MTU size of 1500 bytes on interface “vlan2”, use the commands:
awplus#
configure terminal
awplus(config)#
interface vlan2
awplus(config-if)#
mtu 1500
To configure an MTU size of 1500 bytes on interfaces “vlan2” to “vlan4”, use the
commands:
awplus#
configure terminal
awplus(config)#
interface vlan2-vlan4
awplus(config-if)#
mtu 1500
To restore the MTU size to the default MTU size of 1500 bytes on “vlan2”, use the
commands
awplus#
configure terminal
awplus(config)#
interface vlan2
awplus(config-if)#
no mtu