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The system must not send ICMPv4 redirects by default.


Finding ID Version Rule ID IA Controls Severity
V-217911 RHEL-06-000080 SV-217911r505923_rule Medium
Sending ICMP redirects permits the system to instruct other systems to update their routing information. The ability to send ICMP redirects is only appropriate for systems acting as routers.
Red Hat Enterprise Linux 6 Security Technical Implementation Guide 2020-09-03


Check Text ( C-19392r376748_chk )
The status of the "net.ipv4.conf.default.send_redirects" kernel parameter can be queried by running the following command:

$ sysctl net.ipv4.conf.default.send_redirects
net.ipv4.conf.default.send_redirects = 0

$ grep net.ipv4.conf.default.send_redirects /etc/sysctl.conf /etc/sysctl.d/*
net.ipv4.conf.default.send_redirects = 0

If "net.ipv4.conf.default.send_redirects" is not configured in the /etc/sysctl.conf file or in the /etc/sysctl.d/ directory, is commented out, or does not have a value of "0", this is a finding.
Fix Text (F-19390r376749_fix)
To set the runtime status of the "net.ipv4.conf.default.send_redirects" kernel parameter, run the following command:

# sysctl -w net.ipv4.conf.default.send_redirects=0

Set the system to the required kernel parameter by adding the following line to "/etc/sysctl.conf" or a config file in the /etc/sysctl.d/ directory (or modify the line to have the required value):

net.ipv4.conf.default.send_redirects = 0

Issue the following command to make the changes take effect:

# sysctl --system