pfsense: IPSec SSH connectivity issue
In this post I will setup an IPSec dynamic route-based vpn tunnel between two pfSense Appliances.
I have two Pfsense firewalls for two sites. Sites are connected to each other with Pfsense IPsec tunnel. I experienced a strange issue, I can’t ssh from one site to a vm to the noter.
$ telnet 192.168.3.1 22 Trying 192.168.3.1... Connected to 192.168.3.1. Escape character is '^]'. SSH-2.0-OpenSSH_7.4
I can get SSH banner with telnet but does not work.
I’ve analyzed this a bit and with wireshark there are a lot of TCP - Retransmissions
If I do a ping with Packet Size of 969 Byte everythin is okay, with 970 there is packetloss.
ping -f 192.168.3.1 -l 969
So there is a Issue with fragmentation. I enabled Maximum MMS in VPN->IPSec->Advanced Settings and set value to 1350
With the upgrade of Pfsense 2.6 this menu is change. It is in System->Advanced->Firewall & NAT