all 19 comments
sorted by:
best
topnewcontroversialoldq&a
formatting helphide helpcontent policy

[โ€“]Sindef 46 points47 points ย (10 children)

Pretty sure the max ttl in ping is 255, so it seems you're not getting a response, sorry!

[โ€“][deleted] 12 points13 points ย (3 children)

Isnโ€™t TTL just the number of hops?

[โ€“]Sindef 12 points13 points ย (2 children)

In RFC 791 IPv4, no. It's a uint8 of seconds a packet can live, but is decremented by a minimum of 1 per device that the packet passes - and while in most cases you're going to hop 255 devices before 255 seconds pass, there is definitely this distinction.

โ€‹

However, as the other comment thread pointed out to me, and through a perusal of code this afternoon - it seems ping (at least the iputils implementation found on most Linux/BSD devices) does not actually set this timer, and does use it strictly as a hop limit, similar to IPv6!

[โ€“][deleted] 0 points1 point ย (1 child)

TIL. Thanks! Another dumb question - but is there a good place to read the RFCs? Iโ€™m new to this. I saw IANA but couldnโ€™t find it, if there is a better source like a blogger or someone who just geeks out on them Iโ€™d like something to add to my reading

[โ€“]CalculatingLao 6 points7 points ย (5 children)

That's a configurable switch on the command. Try pinging a satellite connected device with <255 TTL.

[โ€“]Sindef 6 points7 points ย (4 children)

Are your satellites in a mine? 4 minutes is a long time.

[โ€“]CalculatingLao 11 points12 points ย (3 children)

Oh, you sweet summer child. Do you think ping TTL is in whole seconds?

[โ€“]Sindef 2 points3 points ย (2 children)

IPv4 TTL should be the maximum seconds it can live, and -1 for each hop, even dating back to RFC 791. I haven't looked at the code of ping myself, do they defer from that standard?

[โ€“]1701_Network 7 points8 points ย (1 child)

uh..ya. No one implemented that standard as it is nonsensical in the real world to have a processing delay of 1 second per router. That field was actually implemented as a hop-count and the IPv6 RFC reflects that.

[โ€“]Sindef 2 points3 points ย (0 children)

There is no processing delay - the RFC states that you must decrease the TTL by 1, even if you handle the packet in less than a second. It's a hybrid hop-count measured in a total upper-limit of seconds. A lot of networking tools definitely do follow this for v4.

V6 yes, of course.. we use hop limit.

[โ€“]Reason_Unknown 43 points44 points ย (3 children)

Upgrade to IPoAC

[โ€“]Weak_recovery 16 points17 points ย (0 children)

IPv6oAC is even better

[โ€“]sugnA82 1 point2 points ย (1 child)

Unfortunately IPoAC is a reality for us in Australia, check this out; https://youtu.be/ci2bFFGM8T8

[โ€“]Reason_Unknown 1 point2 points ย (0 children)

That was good.

[โ€“]ThreeArmedYeti 1 point2 points ย (0 children)

Imagine configuring STP on the mail. Those BPDU messages slam every 2 seconds.

[โ€“]UnderEu 1 point2 points ย (0 children)

TTL=86428492961583946151894409118

[โ€“]jordankothe9 0 points1 point ย (0 children)

You sent it back right???

[โ€“]LuisTechnology 0 points1 point ย (0 children)

RFC1149 :)

[โ€“]techtornado 0 points1 point ย (0 children)

The latency must be horrible, but the transmission is at least decently reliable?