Hi,

Recently when testing a tunnel connection between a FreeBSD box and a Mikrotik RB1000 ROS 3.26 I found a problem
with 1500 unit packets, packets with this size can't pass thru tunnel, any other with smaller size can pass without
any problem. My tunnel configuration is:

freebsd:
sbin/ifconfig gif1 create
/sbin/ifconfig gif1 tunnel 172.16.100.3 172.16.100.50 netmask
255.255.255.248 mtu 1476
/sbin/ifconfig gif1 inet 192.168.1.1 192.168.1.2 netmask
255.255.255.252 mtu 1476


mikrotik:
/interface ipip add comment="" disabled=no local-address=172.16.100.50 mtu=1476 name=ipip1 \
remote-address=172.16.100.3
/ip address add comment="" disabled=no address=192.168.1.2/30 interface=ether2 broadcast=192.168.1.3 network=192.168.1.0

Tested with 1440, 1420 and 1480 MTU and no luck, also tested with set-mss and no luck too.

Thanks for any help,
Jorge

1500 bytes physically can't pass that interface because you have set mtu=1476.

Changed tunnel mtu to 1500, same result!

And... packets bigger than 1476 not supposed to be fragmented?