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MTU on port with tagged VLAN
The default for the MTU configuration on all ports is 1518, while a VLAN tagged ethernet frame can be as large as 1522 with a L3 payload MTU of 1500. Should I change all MTU values to 1522 for ports ...
Hi firstsn，
Yes， all right.
In the 'Monitoring / Port Detailed Statistics' menu, 'Packets Transmitted > 1518 Octets it include 4 bytes VLAN-tag.
Regards
Carl
Hi fritsn
Sorry，I wrongly assumed your refering to a L3 issue. You are right only routers can fragment frames, not L2 switches.
For GS748T , the MTU not include vlan tag.
For example,
Set port mtu at 1518
untag package size 1518------pass
untag package size 1519（or larger）-----drop
tag package size 1522------pass
tag package size 1523（or larger）-----drop
Hope it helps
Regards
Carl
Hi Carl,
When I said MTU earlier, I really meant the 'Maximum Frame Size' configuration in the 'Switching / Ports' menu.
So you say this:
The VLAN tag is not counted against the Maximum Frame Size, so there is no need to put the number to 1522 for VLAN tagged ports if a normal MTU of 1500 is used for the payload.
True?
In the 'Monitoring / Port Detailed Statistics' menu, I see for a VLAN tagged port: 'Packets Transmitted > 1518 Octets'.
Does the packet size in this menu include the 4 bytes VLAN-tag?
Regards,
Frits
Hi firstsn，
Yes， all right.
In the 'Monitoring / Port Detailed Statistics' menu, 'Packets Transmitted > 1518 Octets it include 4 bytes VLAN-tag.
Regards
Carl
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