How to clear Don't Fragment (DF) bit

Well... I do network design. And 3rd level network support. Wherever my clients have PMTU problems, it's always solved by a little education in the direction of the admin who is blocking ICMP.

 

 

Disabling PMTU will not necessarily disable the DF bit. A better scheme is to just drop the remote MTU to the end-point. With most decent OS's (e.g. Linux) that can be done with an entry in the routing table.

 

 

Dropping the local MTU is a horrible hack, and liable to issues (Performance is a particular one. A lower MTU means lower throughput). The specs say all local MTU's should be identical for a reason.

 

 

H