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I was playing around with ping command and I noticed that despite changing value of -i parameter (and therefor receiving message about TTL expired) there was no packet loss.

Could someone please explain to me why is that so?

Result of ping command

zajer
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2 Answers2

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I see your question about you received TTL Expired in Transit when you ping google without packet loss.

I assume you reduced the TTL value to a very low count as you mentioned you played with the -i parameter.

For example, if I ping the Google DNS address 8.8.8.8 with a lower ping TTL parameter (ping 8.8.8.8 -i 3), it will definitely end with TTL Expired in Transit.

The ping packets will expire on the third hop. It will result in TTL Expired in Transit message on the command prompt.

However, the interesting fact is the ping statistics. The command prompt will show you 0 packet loss.

It is because, as per the network condition, there is no packet loss. They just expire before reaching the destination.

Command prompt received the proper acknowledgment in each hop till the packets expire.

Reference: https://www.corenetworkz.com/2011/05/ttl-expired-in-transit-reason-and.html

Allan
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  • I guess it is worth to mention that on GNU/Linux systems reducing the TTL to a value where it is impossible to reach a destination is equal to losing a packet. Specifically `ping -t 3 8.8.8.8` on Debian results in "Time to live exceeded, 100% packet loss". – zajer Mar 29 '22 at 13:02
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Every time an IP packet goes through a router (layer 3 interface) the TTL is reduced.

If the TTL gets to 0 the router drops the packet and sends an ICMP error indicating TTL expired in transit.

In my experience this symptom frequently indicates a routing loop.

If you do tracert to the same address it will show the path through the network, and I suspect that it will reveal that there is a routing loop (you will see the same pair of addresses multiple times in the tracert results).

Zed
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  • Totally agree but why no packets are lost despite TTL being expired ? None of them reached desired destination and still all of them are considered as delivered. – zajer May 01 '18 at 12:59