Server Fault is a question and answer site for system and network administrators. It's 100% free, no registration required.

Sign up
Here's how it works:
  1. Anybody can ask a question
  2. Anybody can answer
  3. The best answers are voted up and rise to the top


I am testing application on linux, and we have a bug related to the database connection, since the database connection cannnot be restarted and it's on a remote machine, I would like to kill the tcp connection in order to interrupt the connection and see the behaviour.

Unplugging the network cable is not an option neither! I don't have physical access on both machines.

I tought about using the iptables, but I don't have iptables on my system, so my project manager told me to use tcpkill to accomplish this.

Can someone tell me where I can get the tcpkill rpm and give me some hints about how to use it?

share|improve this question
up vote 10 down vote accepted

Add a null route with ip route blackhole, assuming you have root:

[root@centos6 ~]# nc -zv 80
Connection to 80 port [tcp/http] succeeded!
[root@centos6 ~]# ip route add blackhole
[root@centos6 ~]# nc -zv 80
nc: connect to port 80 (tcp) failed: Network is unreachable
[root@centos6 ~]# ip route delete blackhole
[root@centos6 ~]# nc -zv 80
Connection to 80 port [tcp/http] succeeded!

EDIT: If you have on the machine and the app connects to the database via a FQDN, add a FQDN and point the FQDN to a dummy address. It may take a while for the tcp connection to drop, though.

EDIT again: Okay, I missed the part about tcpkill. :)

It available in EPEL, which, if you are running CentOS or Scientific Linux, you enable the EPEL repo so that you can find it:

[root@kerberos rsync-dist]# yum whatprovides "*/tcpkill" --enablerepo=epel
Loaded plugins: refresh-packagekit
epel/metalink                                                                                                                                                              | 9.0 kB     00:00     
epel                                                                                                                                                                       | 4.3 kB     00:00     
epel/primary_db                                                                                                                                                            | 4.3 MB     00:05     
epel/filelists_db                                                                                                                                                          | 5.5 MB     00:07     
dsniff-2.4-0.9.b1.el6.x86_64 : Tools for network auditing and penetration testing
Repo        : epel
Matched from:
Filename    : /usr/sbin/tcpkill

Make sure to use the --enablerepo so that you can install from there, like this:

yum -y install dsniff --enablerepo=epel

You can read the instructions here:


tcpkill ip host and not
share|improve this answer
changing DNS will not kill existing tcp connection – Sandman4 Dec 6 '11 at 6:35
You are right. At best, the connection will just time out. I just provided that in case he does not have the iproute2 package installed (not likely at this, but you never know). – Rilindo Dec 6 '11 at 14:07

Your Answer


By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.