Forum Discussion

Craig_05_144607's avatar
Craig_05_144607
Icon for Nimbostratus rankNimbostratus
Feb 18, 2014

Destination Unreachable "reduce MTU size" message not passing back through F5 LTM for MS Exchange traffic

MS Exchange mail traffic from our F5 LTM is reaching a tunnel which is requiring the Exchange Servers to adjust the MTU. An ICMP message "Destination Unreachable" which contains the reduce MTU messag...
application delivery
devops
iRules
LTM
Mui_64918's avatar
Mui_64918
Icon for Cirrus rankCirrus
Feb 18, 2014

There is a bug with MSS adjust, check the version you are running. In F5 you can work around by changing the MTU for the vlan to the lowest MTU of the TUNNEL or you can selectively set for the VLAN or the path.