live45 ptscloses 11/12/2026, 10:07:33 PM

SSH freezes after exactly one screenful

Over the VPN, any command that prints more than ~1400 bytes freezes your SSH session forever. `ls` fine. `cat` doom.

The scene

Reported: office VPN users: ls and uptime are fine, but cat big.log or journalctl freezes the session mid-output. After ~2 minutes the connection dies.

$ ping -M do -s 1372 bastion   # 1400 bytes on the wire
100% packet loss
$ ping -M do -s 1172 bastion
0% packet loss

The VPN tunnel interface MTU is 1420. The server's eth0 MTU is 1500.
Corporate firewall policy: "drop all ICMP — it's a recon vector".
ss -ti on the server shows mss:1448 toward VPN clients.

The scene

Diagnoses — hidden until the incident closes