Re: Can't ping local computers

From: Tron Thomas (tron.thomas_at_verizon.net)
Date: 07/20/04 

Date: 19 Jul 2004 18:58:05 -0700

Allen Kistler <ackistler@oohay.moc> wrote in message news:<7ZcKc.37765$eH1.18147955@newssvr28.news.prodigy.com>...
> Jerry Smiley wrote:
> > Check to make that each Linux box does not have a firewall setup that blocks
> > the icmp ping..
>
> It _is_ possible that you allow outgoing echo requests and incoming
> replies on both boxes (ping works to the router), but block incoming
> requests or outgoing replies (ping fails to each other).
>
> That's not likely for Windows unless you purchased a firewall or are
> testing SP2, since Windows only filters by tcp/udp port and ip protocol.
> The fact that both can talk to the router rules out wiring or netmask
> problems.
>
> If you have arping (only works on local networks), you can try that from
> the Linux box. arping uses arp packets instead of icmp packets.
>
> tcpdump comes with most Linux distributions. If you run it on the Linux
> box when you try to ping one way or the other, it will provide you with
> a little more info.
>
> tcpdump -ni eth0 [... or something similar. It's really flexible.]
>
> 1. Do you get a successful arp (who-has and is-at packets)?
> 2. Does the icmp echo request go out? Is there an icmp reply?

I have arping. I tried /usr/sbin/arping [Macintosh Computer Name].
The result I got was:

arping: socket: Operation not permitted

I do not have tcpdump on my Linux system.

What do I need to do to see if I get a successful arp?
How do I test the icmp echo request and icmp reply?

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