* [Sat, Aug 24, 2013 at 11:15:42AM +0300] Georgi Naplatanov:
Hi, I want my machine to ignore ICMP redirects in Debian Wheezy (Linux kernel)

Does

net.ipv4.conf.all.accept_redirects = 0

in /etc/sysctl.conf make kernel to ignore ICMP redirects for all interfaces

or

1) do I have to set it for particular interface like net.ipv4.conf.eth0.accept_redirects = 0

or

2) do I have to set a rule in iptables like

iptables -A INPUT -i eth0 -p icmp --icmp-type 5 -j DROP

Using sysctl vs. iptables is probably a matter of taste. I usually prefer the former but often includes rules for the latter in order not to be hit when porting the packet filtering script to another host. As for the accept_redirects sys parameter, the following is from Documentation/networking/ip-sysctl.txt.gz (kernel 3.10):

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
    or
- 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)

Ciao,
Gian Piero.


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  • ICMP redirects Georgi Naplatanov
    • Re: ICMP redirects Gian Piero Carrubba

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