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Finding IPv4 foreign address and disabling IPv6 - SOLVED -
https://forum.linode.com/viewtopic.php?f=19&t=3513
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Author:  dippa [ Thu Sep 11, 2008 4:45 am ]
Post subject:  Finding IPv4 foreign address and disabling IPv6 - SOLVED -

Hi,

I'm trying to get the IPv4 source address for SSHD connection however netstat is dropping the last octet.
---
root@node1:~# netstat -taupen | grep 22
tcp6 0 0 :::22 :::* LISTEN 0 1946 1276/sshd
tcp6 0 104 ::ffff:67.18.187.222:22 ::ffff:125.255.80.:3492 ESTABLISHED0 2014 1305/sshd: sharpeg
---

As I dont need to use IPv6 I tried disabling it (in /etc/modprobe.d/aliases):
---
# alias net-pf-10 ipv6 //Disabled IPv6 20080911
alias net-pf-10 off
alias ipv6 off
---

Didn't disable IPv6 however checking modules list there is nothing to disable (linode use motholithic kernels):
---
root@node1:~# lsmod
Module Size Used by
root@node1:~#
---

So guess I have two questions:
1. is it possible to get a kernel with IPv6 disabled?
2. how to find the IPv4 address of connections to my linode host?


Thanks

Author:  SelfishMan [ Thu Sep 11, 2008 4:56 am ]
Post subject: 

You can disable IPv6 support for most services. For example, to disable it for SSHd edit your config and add the line "AddressFamily inet" and make sure "ListenAddress ::" is commented out. Restart the service and you should see only IPv4 addresses. Your current SSH session will still show in IPv6 format but only until you disconnect.

Author:  dippa [ Thu Sep 11, 2008 8:52 am ]
Post subject:  Fixed!

thanks SelfishMan the "ADdressFamily inet" did the job, "ListenAddress ::" was already commented out.

After a bit more investigating to the netstat -n truncation of the ip6 address I found an open bug report:
http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=254243

For those that encounter the same thing under Debian Etch you can either:
- re-package the a patched net-tools or
- install the testing net-tools package which has the patch applied, which is what I did

I can now see the full ip6 address:
---
root@node1:~# netstat -taupen | grep 22
tcp6 0 0 :::22 :::* LISTEN 0 17027 2516/sshd
tcp6 0 0 67.18.187.222:22 220.239.42.204:1918 ESTABLISHED 0 17111 2543/sshd: sharpeg
tcp6 0 52 67.18.187.222:22 220.239.42.204:1917 ESTABLISHED 0 17035 2518/sshd: sharpeg
---

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