What Does This Reply To "ping" Mean?

Issued ping command:

gary@suselinux:~> ping 192.168.254.253

Response from command:

----------------------------------snip----------------------------------
PING 192.168.254.253 (192.168.254.253) 56(84) bytes of data.
From 192.168.254.254: icmp_seq=1 Time to live exceeded
From 192.168.254.254 icmp_seq=2 Time to live exceeded
----------------------------------snip----------------------------------

I tried to ping 192.168.254.253 which is presently an unknown (was not always an unknown)
the response says "From 192.168.254.254". 192.168.254.254 is my modem/router.
why is the modem/router responding?
what is icmp_seq?
what is it trying to tell me with the message "Time to live exceeded"

The Internet Control Message Protocol (ICMP) [RFC792] protocol is classic example of a client server application. The ICMP server executes on all IP end system computers and all IP intermediate systems (i.e routers). The protocol is used to report problems with delivery of IP datagrams within an IP network. It can be sued to show when a particular End System (ES) is not responding, when an IP network is not reachable, when a node is overloaded, when an error occurs in the IP header information, etc. The protocol is also frequently used by Internet managers to verify correct operations of End Systems (ES) and to check that routers are correctly routing packets to the specified destination address.

Many routers and servers are disable IVMP, so PING command does not reqonice them
See more :
ICMP
Wiki

Issued ping command:

gary@suselinux:~> ping 192.168.254.253

Response from command:

----------------------------------snip----------------------------------
PING 192.168.254.253 (192.168.254.253) 56(84) bytes of data.
From 192.168.254.254: icmp_seq=1 Time to live exceeded
From 192.168.254.254 icmp_seq=2 Time to live exceeded
----------------------------------snip----------------------------------

I tried to ping 192.168.254.253 which is presently an unknown (was not always an unknown)
the response says "From 192.168.254.254". 192.168.254.254 is my modem/router.
why is the modem/router responding?
what is icmp_seq?
what is it trying to tell me with the message "Time to live exceeded"
[/b]

Hi,

icmp_seq is the number of ping attempts. As already mentioned ping uses icmp protocol to send icmp echo requests to network hosts. Every IP packet has a time to live (TTL) field in the IP header. It should prevent that an undeliverable IP packet will live endless in the network. The TTL is decreased on every hop (router) and when the TTL exceeds the packet gets dropped.

I think in you special case you may have an endless loop in your network routing

Gentlemen, thank you for the reply.

I think in you special case you may have an endless loop in your network routing [/b]

Knowing what I was trying to do, I think Monex may have hit the nail on the head. This would explain some other things going on.


Gary