How to clear Don't Fragment (DF) bit

Unfortunately that's not been my experience, particularly where firewalls and router ACLs are concerned. Even where you can control and 'fix' these internally, external and internet sourced connections still present a problem. I've always found it simpler and to be blunt, more reassuring to just drop the VLAN MTU by 160 or so (no great loss).

 

 

BTW, do you know if disabling PMTU would also stop use of the DF bit? What I've read suggests that may be the case.