Take the 2-minute tour ×
Network Engineering Stack Exchange is a question and answer site for network engineers. It's 100% free, no registration required.

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

share|improve this question
    
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 at 19:20
3  
Nobody builds 500 hop networks, this question is really strange –  Mike Pennington Feb 25 at 22:46
    
Ahem tracert -h 255 -w 100 obiwan.scrye.net –  user3490 Feb 25 at 23:06
4  
@user3490, it's called a routing loop. That doesn't qualify as a real network diameter –  Mike Pennington Feb 26 at 3:07

1 Answer 1

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.

share|improve this answer
7  
Minor addition: unless some of the hops are hidden by tunnels :) –  Sander Steffann Feb 25 at 20:42

Your Answer

 
discard

By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.