I have a strange behaviour on a Balance One at one of our remote offices in Spain. For some reasons it seems that packets going through the Pepvpn are not fragmented. I detected this problem when an access point with 802.1x authentication wasn’t reaching the radius server in the HQ in Sweden.
The WAN is connected to a ADSL modem in bridgmode. The WAN interface runs PPPOE and the MTU is set to automatic which show in the dashboard 1492. When testing from a client to ping with the Don’t Fragment flag set, the larges value is 1464 as expected.
When I setup a Pepvpn to a Balance 710 at our HQ in Sweden, I cannot ping with a size larger than 1412 no matter if the DF flag is set or not. I tested to change the MTU to default 1440 on the WAN interface but then the largest size I can ping is 1364. I also tried with an IPSec tunnel which gave me an even smaller size of 1314.
Probably the fault is not at the Balance but could someone give me tips where to look to find the problem?