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Manouchehri/get_ephemeral_port.sh

Last active January 31, 2025 12:13
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Get a random ephemeral port number
Raw
get_ephemeral_port.sh
shuf -i 49152-60999 -n1
# This obeys:
# RFC 6335 49152-65535 - https://www.rfc-editor.org/rfc/rfc6335.html
# Linux 32768-60999 - https://github.com/torvalds/linux/blob/1f5abbd77e2c1787e74b7c2caffac97def78ba52/net/ipv4/af_inet.c#L1833-L1834
# Windows 49152-65535 - https://learn.microsoft.com/en-US/troubleshoot/windows-server/networking/default-dynamic-port-range-tcpip-chang
# Why does this matter? Naively, this gives us the best chance of not having our port changed when going through NAT.
# In reality, it probably doesn't help.
Raw
set_safer_range.sh
sysctl -w net.ipv4.ip_local_port_range="49152 60999"
# Hopefully avoid NAT port changing more
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