TCP/IP Packet DF Flag 'always' set
807559Feb 29 2004 — edited Mar 14 2004Hi
I am running Solaris 9 Ultra 10 over PPPoE -- my actual network is as follows -
Solaris 9 Private IP MTU 1500 -> Wireless Ethernet Bridge
Linksys Wireless DSL Modem MTU 1492 PPPoE to DSLAM (mtu?)
Everything works EXCEPT a few SMTP systems cannot send me mail - this was traced to a MTU issue.
This has plagued me for months and I have performed many tests with various platforms and operating systems (Solaris, SuSE Ultra Penguin, and Debian Ultrasparc.)
The Debian Ultrasparc release works the best but there is next to no software similar to what I need under Solaris (my day job is - funny - Solaris SysAdmin.)
My research has show thus far that it might be related to IPv6-IPv4 routing (IPv6 forces DF flag to be set always according to RFCs.) However I am not using IPv6 (but the thing has IPv6 netstat -a results ? starnge huh.)
I am not sure what I can do to get the DF flag off and allow the packet to fragment when required.
I am at a loss and I need Solaris 9 to work correctly. Any input or other ideas would be most appreciated.
Thx/Sx