What is the right security setting for the net.ipv4.conf.all.secure_redirects option in sysctl.conf? Here it sets to 1 and Here sets to 0. Is net.ipv4.conf.default.secure_redirects related to previous? and ٌWhat is the right setting for it?


1st link (wiki.ubuntu.com) stated:

The following sysctl settings are default at the time of this writing. We intend that they stay this way.

net.ipv4.conf.all.secure_redirects = 1. 

Prevents hijacking of routing path by only allowing redirects from gateways known in our routing table.

2nd link (joshrendek.com) states:

# Make sure no one can alter the routing tables 
net.ipv4.conf.all.accept_redirects = 0
net.ipv4.conf.default.accept_redirects = 0
net.ipv4.conf.all.secure_redirects = 0
net.ipv4.conf.default.secure_redirects = 0
  • Interesting question. Though there is a slight difference in wording regarding the 2 settings.
    – Rinzwind
    Apr 17, 2014 at 7:35

1 Answer 1


When looking at this I used Fedora as a reference (to see how another OS looks at this) (edit: these are Fedora's thoughts on setting up a SERVER! See the bottom part for why this is important):

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accept_redirects - BOOLEAN
    Accept ICMP redirect messages.
    accept_redirects for the interface will be enabled if:
    - both conf/{all,interface}/accept_redirects are TRUE in the case
      forwarding for the interface is enabled
    - at least one of conf/{all,interface}/accept_redirects is TRUE in the
      case forwarding for the interface is disabled
    accept_redirects for the interface will be disabled otherwise
    default TRUE (host)
        FALSE (router)

Here is an interesting blog. Conclusion:

This arcane logic means that for a non-router (i.e. most servers), not only must /proc/sys/net/ipv4/conf/all/accept_redirects be 0, but so must /proc/sys/net/ipv4/conf/interface/accept_redirects.

So ...

  • if you are using your system as a server set it to 0.
  • if you are using your system as a desktop you can leave it on 1 (but can set it to 0 if you want to harden your system).

Both can be considered correct (and sane).

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