[CentOS] 2 questions on CentOS firewall

Timothy Murphy gayleard at eircom.net
Wed Jul 20 18:51:09 UTC 2011

Markus Falb wrote:

> I would use tcpdump on the CentOS Server to be sure the icmp echo
> requests are arriving or not. tcpdump is something like ethereal but it
> could be as easy as
> $ tcpdump -l proto \\icmp
> or
> $ tcpdump -l proto \\icmp and host sourceip
> or
> $ tcpdump -li ethX proto \\icmp
> or
> ...

Thanks for the instructions.
Nothing seems to get through:
[tim at helen ~]$ ping anghiari.homelinux.com
PING anghiari.homelinux.com ( 56(84) bytes of data.

--- anghiari.homelinux.com ping statistics ---
3 packets transmitted, 0 received, 100% packet loss, time 2000ms

[root at alfred tim]# tcpdump -l proto \\icmp
tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on eth0, link-type EN10MB (Ethernet), capture size 65535 bytes


So I assume the modem is rejecting the ICMP packets.
As I said, I don't see anything about this
in the modem documentation or on the modem web-site.

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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