[CentOS] 2 questions on CentOS firewall

Timothy Murphy gayleard at eircom.net
Tue Jul 19 17:19:11 UTC 2011

Ljubomir Ljubojevic wrote:

>> (1) I can open port 22 on the Billion, allowing me to ssh in from
>> outside. But for some reason I cannot ping the same address from outside.

> This is due to modem refuses to answer to pings. You might have option
> to allow it in modem config.
> Ping (ICMP) does not use ports but it is packet of type 8.

Thanks again for your response.
Could CentOS be preventing me from pinging the system?

> When you turn off firewall, it stops routing packets so they can not be
> passed to systems behind it.
> Only option I can think of is to use shorewall as firewall and add
> NAT/Masquerade and the rest of the rules to routestoped confgi file:

I was using Shorewall before I went over to CentOS-6,
and will probably go over to it.

But I don't really need to disable the firewall on the server.
I just thought I'd try it as an experiment.

Timothy Murphy  
e-mail: gayleard /at/ eircom.net
tel: +353-86-2336090, +353-1-2842366
s-mail: School of Mathematics, Trinity College, Dublin 2, Ireland

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