[Netkit.users] Issue with vlan/mtu

[ZioPRoTo (Saverio Proto)]

Hold on, you mean that the Linux box is VLAN unaware, and the the IP
packet transits towards a VLAN aware segment ??

In this case OF COURSE the first switch at the edge of the VLAN aware
segment of the Network will fragment the packet if HIS MTU is not
bigger than 1500. This is the normal behaviour as far as I know.

The REAL solution is having a MTU of  at least 1504 bytes in the VLAN
aware network

There is not ICMP message for indicating that IP packets are being
fragmented. The only case is when the Dont' Fragment bit is set, and
packet is dropped, in that case you get back an ICMP

Have a look here.

http://www.ietf.org/rfc/rfc1700.txt
http://www.uniroma2.it/didattica/reti-accesso/deposito/5_vlans.pdf

my 2 cents

Saverio Proto