Archive for the ‘Network Info’ Category
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Donnerstag, Oktober 2nd, 2025Docusnap 14 – HPE Garantie Check einfach erklärt
Donnerstag, Oktober 2nd, 2025FRITZ!Tech – eine Kindersicherung einrichten
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Mittwoch, September 24th, 2025FRITZ!Tech – ‚Zack‘ der Speedtest für ihre Breitbandverbindung
Montag, September 22nd, 2025
TCP Keepalive is a standard OS level mechanism for detecting dead connections by periodically sending probe packets on idle TCP connections – both Windows and Linux default to 2 hours (7.200 seconds) before sending the first keepalive probe
Freitag, September 19th, 2025
Always set keepalive less than firewall timeout with intvl and probes tuned for your use case
Linux Parameter ‚tcp_keepalive_time‘ – sets the idle time (in seconds) a TCP connection must remain inactive before the kernel starts sending keepalive probes to check if the other end is still responsive and the default value is 7.200 seconds (2 hours)
Mittwoch, September 17th, 2025The tcp_keepalive_time is part of a three-parameter system:
tcp_keepalive_time – the initial idle time before the first probe is sent (default: 7.200 seconds)
tcp_keepalive_intvl – the interval (in seconds) between subsequent keepalive probes if the previous one doesn’t receive an acknowledgment (default: 75 seconds)
tcp_keepalive_probes – the number of failed probes after which the connection is considered broken and is closed (default: 9)
root@pve-ubuntu-01:~# sysctl net.ipv4.tcp_keepalive_time net.ipv4.tcp_keepalive_intvl net.ipv4.tcp_keepalive_probes
net.ipv4.tcp_keepalive_time = 7200
net.ipv4.tcp_keepalive_intvl = 75
net.ipv4.tcp_keepalive_probes = 9
root@pve-ubuntu-01:~#
Change temporarily for testing:
root@pve-ubuntu-01:~# sysctl -w net.ipv4.tcp_keepalive_time=900 # Sets the time to 15 minutes
root@pve-ubuntu-01:~# sysctl -a | grep keep
net.ipv4.tcp_keepalive_intvl = 75
net.ipv4.tcp_keepalive_probes = 9
net.ipv4.tcp_keepalive_time = 900
net.ipv6.conf.all.keep_addr_on_down = 0
net.ipv6.conf.default.keep_addr_on_down = 0
net.ipv6.conf.eth0.keep_addr_on_down = 0
net.ipv6.conf.lo.keep_addr_on_down = 0
Always set keepalive less than firewall timeout with intvl and probes tuned for your use case