I upgraded my router from 19.07.4 to 21.02.0-rc4 a couple of weeks ago.
Just figured today when using my Openvpn for first time that something odd is going on.
After I setup the tunnel from external to internal pings (ICMP) and DNS requests are working no issue but TCP communication get stuck. Means e.g. if I open a ssh connect to a device behind the router a couple of packages goes through but connection not established.
SSH client debug ends with
debug1: kex: server->client cipher: chacha20-poly1305@openssh.com MAC: <implicit> compression: none
debug1: kex: client->server cipher: chacha20-poly1305@openssh.com MAC: <implicit> compression: none
debug3: send packet: type 30
debug1: expecting SSH2_MSG_KEX_ECDH_REPLY
Could this be a MTU issue and how could it be related to the upgrade?
These are the MTU info from the log file
Control Channel MTU parms [ L:1624 D:1182 EF:68 EB:0 ET:0 EL:3 ]
Data Channel MTU parms [ L:1624 D:1400 EF:124 EB:406 ET:0 EL:3 ]
Local Options String (VER=V4): 'V4,dev-type tun,link-mtu 1560,tun-mtu 1500,xxxx
Expected Remote Options String (VER=V4): 'V4,dev-type tun,link-mtu 1560,tun-mtu 1500,xxxx
Client_01/14.0.171.5:55761 Data Channel MTU parms [ L:1552 D:1400 EF:52 EB:406 ET:0 EL:3 ]