sinshiva
Very Senior Member
Originally, i was lazy and used link-mtu to figure out tun-mtu. however, i since did some poking around and found this;
http://openvpn.net/archive/openvpn-users/2004-11/msg00649.html
according to this, if you use sha256 HMAC (32byte signature instead of sha1's 20byte) and UDP, it appears the tun-mtu should be WANMTU- 81bytes for a tun-mtu of 1419 if you have a WANMTU of 1500. (mssfix and fragment would be 1415; tun-mtu -4)
and if you use sha256 HMAC with TCP, tun-mtu should be WANMTU-93bytes for a tun-mtu of 1407 with a WANMTU of 1500.
as i'm personally using a WANMTU of 1456, my tun-mtu's are less, of course.
http://openvpn.net/archive/openvpn-users/2004-11/msg00649.html
according to this, if you use sha256 HMAC (32byte signature instead of sha1's 20byte) and UDP, it appears the tun-mtu should be WANMTU- 81bytes for a tun-mtu of 1419 if you have a WANMTU of 1500. (mssfix and fragment would be 1415; tun-mtu -4)
and if you use sha256 HMAC with TCP, tun-mtu should be WANMTU-93bytes for a tun-mtu of 1407 with a WANMTU of 1500.
as i'm personally using a WANMTU of 1456, my tun-mtu's are less, of course.
