DE

↑ ↓ select, Enter open, Esc close

Test the MTU with ping

harmlessNetworkalle
Adjust the values, the command updates live
user@server
ping -M do -s 1472 -c 3 example.com

Sends three pings with the given payload and prohibits fragmentation. A payload of 1472 bytes plus 28 bytes of headers equals the usual MTU of 1500. If message too long appears or no reply arrives, reduce the size step by step until it works.

Note: MTU problems are typical with VPNs, tunnels and PPPoE connections. Symptom: small requests work, while large pages or uploads hang.

Also searched as

  • how to find mtu size with ping
  • ping do not fragment linux
  • large uploads hang mtu problem

Related one-liners

All in Network

Capture network traffic on a port with tcpdump

#tcpdump -i any -nn -c 100 port 25
harmlessNetwork

Find the route and source IP for a destination

$ip route get 1.1.1.1
harmlessNetwork

Analyze server errors (5xx) in the access log

#awk '$9 ~ /^5[0-9][0-9]$/ {print $9, $7}' /var/www/vhosts/system/example.com/logs/access_ssl_log | sort | uniq -c | sort -rn | head -20
harmlessLogs

Check all MySQL tables for errors

#mysqlcheck --all-databases --check --silent
harmlessMySQL and MariaDB

Check all PHP files in a directory for syntax errors

$find /var/www/vhosts/example.com/httpdocs/wp-content/themes -name '*.php' -exec php -l {} \; 2>&1 | grep -v '^No syntax errors'
harmlessPHP

Check permissions along a path

$namei -l /var/www/vhosts/example.com/httpdocs/index.php
harmlessPermissions and ownership

Read first, then run.

The commands on myline.de act directly on servers, files and databases. A wrong path or placeholder can delete data irreversibly or make a server unreachable.

  • All commands are provided without warranty and are not tested on every system.
  • Understand what a command does before running it, and check every placeholder.
  • Make a backup first and, if possible, try it on a test system.
  • You run commands at your own risk. Liability for damages is excluded to the extent permitted by law.