8

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

5
  • 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
    – This
    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. That doesn't qualify as a real network diameter
    – This
    Feb 26 '14 at 3:07
  • 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 3 at 18:45
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.

1
  • 8
    Minor addition: unless some of the hops are hidden by tunnels :) Feb 25 '14 at 20:42

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