We have some routers that are going over a GRE tunnel and have IPSec encryption. THis is done over a 3G line. We were experiencing problems with certain applications being slow and changed the mtu size from 1514 to 1420. This improved the connection to our applications but now they are having issues getting to certain internet sites. Has anyone seen this issue before? Is there a fix to it?
This is our tunnel config...
ip address 10.10.5.6 255.255.255.252
ip tcp adjust-mss 1420
tunnel source Cellular0/1/0
tunnel destination 18.104.22.168