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caveman
Asked: 2020-08-11 10:56:45 +0800 CST

How to change hop limit of IPv6 in Linux?

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net.ipv6.conf.all.accept_ra_min_hop_limit = 1
net.ipv6.conf.all.hop_limit = 65
net.ipv6.conf.default.accept_ra_min_hop_limit = 1
net.ipv6.conf.default.hop_limit = 65
net.ipv6.conf.enp0s25.accept_ra_min_hop_limit = 1
net.ipv6.conf.enp0s25.hop_limit = 65
net.ipv6.conf.lo.accept_ra_min_hop_limit = 1
net.ipv6.conf.lo.hop_limit = 65
net.ipv6.conf.wlp7s0.accept_ra_min_hop_limit = 1
net.ipv6.conf.wlp7s0.hop_limit = 65

But when I ping, wireshark shows me hop limit is still 64. What is going on?

Using Arch Linux.

linux networking ipv6 linux-networking

1 Answers

  1. The ping utility creates raw packets with their own hop limit set. By default ping uses a hop limit of 64, but you can change it with the -t option.

    ping -6 -c1 -t128 www.google.com

    Wireshark packet capture showing Hop limit: 128

    If you mean to check whether outgoing traffic has the hop limit set correctly as in your sysctl, you should create some real traffic using something like your actual workload.

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