8

As the ttl is 255 maximum for ipv4 on cisco routers, will ping work if there are 500 routers between pc1 and pc2?

Teun Vink
  • 16,953
  • 6
  • 44
  • 70
ban_ra
  • 89
  • 1
  • If you controlled the routers, then I suppose it would be possible to use some sort of encapsulation techniques (GRE Tunnels). But by purely routing along the path, doubtful. – Ryan Foley Feb 25 '14 at 19:20
  • 4
    Nobody builds 500 hop networks, this question is really strange – Mike Pennington Feb 25 '14 at 22:46
  • Ahem `tracert -h 255 -w 100 obiwan.scrye.net` – user3490 Feb 25 '14 at 23:06
  • 5
    @user3490, it's called [a routing loop](http://beaglenetworks.net/post/42707829171/star-wars-traceroute). That doesn't qualify as a real network diameter – Mike Pennington Feb 26 '14 at 03:07
  • Did any answer help you? if so, you should accept the answer so that the question doesn't keep popping up forever, looking for an answer. Alternatively, you could post and accept your own answer. – Ron Maupin Jan 03 '21 at 18:45

1 Answers1

13

The TTL field itself in the IPv4 header is 1 byte, which leaves a maximum decimal value of 255 regardless of the vendor of the router.

Pursuant to RFC 1812, the answer to your question is no. Every router is required to decrement the TTL value by 1 whenever it receives an IPv4 packet. You would receive ICMP "Time Exceeded" messages on the source host from which you are running the ping. More information on the TTL field can be found in the RFC.

Community
  • 1
John Jensen
  • 8,997
  • 4
  • 29
  • 47