RB450G - l2 mtu

Hardware MikroTik hardware general
1

Hello forum, i have a question about l2 mtu.

Why is l2 mtu different in ros 5.5 and ros 5.9 ?

5.5
/interface ethernet> print detail
Flags: X - disabled, R - running, S - slave
0 R name=“ether1-uplink” mtu=1500 l2mtu=1524 mac-address=xx:xx:xx:xx:xx:xx arp=enabled
auto-negotiation=yes full-duplex=yes speed=100Mbps master-port=none bandwidth=unlimited/unlimited
switch=switch1

5.9

/interface ethernet print detail
Flags: X - disabled, R - running, S - slave
0 R name=“ether1-uplink” mtu=1500 l2mtu=1520 mac-address=xx:xx:xx:xx:xx:xx arp=enabled auto-negotiation=yes full-duplex=yes speed=100Mbps master-port=none
bandwidth=unlimited/unlimited switch=switch1


5.17

/interface ethernet> print detail
Flags: X - disabled, R - running, S - slave
0 R name=“ether1-uplink” mtu=1500 l2mtu=1520 mac-address=xx:xx:xx:xx:xx:xx arp=enabled auto-negotiation=yes full-duplex=yes speed=100Mbps master-port=none
bandwidth=unlimited/unlimited switch=switch1

4.17

/interface ethernet print detail
Flags: X - disabled, R - running, S - slave
0 R name=“ether1-uplink” mtu=1500 l2mtu=1524 mac-address=xx:xx:xx:xx:x:xx arp=enabled auto-negotiation=yes full-duplex=yes speed=100Mbps master-port=none
bandwidth=unlimited/unlimited switch=switch1


Thanks L.

2

Happened with the 5.7 release, questions were asked at that time and what answers there were seemed to indicate that it was to work around some kind of hardware problem vague recollection says it was related to the switch chips since it varies with which hardware uses which chips.

http://forum.mikrotik.com/t/l2mtu-decreased-on-g-series-after-upgrade-to-5-7/51616/1

http://forum.mikrotik.com/t/routeros-v5-7-released/50130/1

http://wiki.mikrotik.com/wiki/Manual:Maximum_Transmission_Unit_on_RouterBoards

3

Thanks, it not seems serious from mikrotik. In ROS 4.x was MTU 1526/1524 and wasn’t problem . 4.x was here long time, why in 5.x?

L.