ping question

Ean Kingston ean at
Sat Feb 12 16:56:53 GMT 2005

On February 12, 2005 11:50 am, ann kok wrote:
> Hi all
> I ping from redhat to cisco router and freebsd router
> but I don't understand ttl (time to live)

ttl is 'time-to-live' it is a counter. Every router that the ping packet goes 
through subtracts 1 from the ttl value. When it reaches 0 (zero), the router 
that got the zero replies with a 'ttl exceeded message'. If the ping packet 
reaches it's destination before the ttl  goes to zero, it replies with a 
'ping reply'. This helps with diagnosis of network configuration issues.

> Cisco router has ttl=251 and freebsd router has 58
> Does it set by the router itself?
> Can I change it in freebsd?

You control the ttl value from the place you send the ping from (in your 
description the RedHat system).

When using ping from FreeBSD the -m parameter is used to set the initial 
value. I believe the initial value can be anything from 0 to 255. The default 
varies from system to system but the most common is 255.

> Thank you
[cut sample ping output]
Ean Kingston

E-Mail: ean AT hedron DOT org

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