TTL decrements by more than 1 for a single hop

Posted on 2009-05-01
Last Modified: 2013-11-25
I have a host I ping and its TTL is 241 yet directly connected off that router is anohter router and its TTL is 113. How is the TTL being dropped by 128 when just one hop involved?
Question by:murphymail
    LVL 2

    Expert Comment

    You have to remember that there are many factors involved here, cable quality, settings for both routers, and even the brand. Even if you have the same of every thing, it could still give you those results because you are still going through multiple hops.
    LVL 23

    Accepted Solution

    Most like there's more than one hop, you just can't see it.   It could be a GRE tunnel, or your path from A to the "next hop" could be through a MPLS  LSP,
    which can have some interesting treatment of TTLs.

    The path in-between could even be different in a way that's invisible in a traceroute, and i.e. can be invisible hops.

    Also, one of the routers on one of the paths could have a 'MAXIMUM TTL'
    i.e. if it receives a TTL greater than 200, reduce to 200.
    Perhaps now would also be a good time to remind you, that there's no rule that a router can only decrement a TTL by one.

    The TTL is actually a timer.   If a router holds a packet in buffers  3 seconds before sending it,  the router may decrement the TTL by 3.

    See RFC 1812   5.3.1  Time To Live (TTL) page 84.

    It's normally not a big issue, since many routers only ever opt to
    decrement by 1 nowadays,   and it shold be rare that a router ever
    holds onto a packet for longer than a fraction of a second, let-alone
    a whole second.


    Author Comment

    I found that the fartest router was using a 128 TTL thatn the ADtran (255) so when factoring in that each router used a different TTL to start and that is what I was seeing on my PING the results made sense. Thanks

    Write Comment

    Please enter a first name

    Please enter a last name

    We will never share this with anyone.

    Featured Post

    New My Cloud Pro Series - organize everything!

    With space to keep virtually everything, the My Cloud Pro Series offers your team the network storage to edit, save and share production files from anywhere with an internet connection. Compatible with both Mac and PC, you're able to protect your content regardless of OS.

    Suggested Solutions

    Title # Comments Views Activity
    Cisco ASA and spanning tree 8 69
    Generating groups 1 32
    Need a "Dead or Alive" program 4 16
    vm nic duplex 1 33
    Broadband over Power Lines Broadband over Power Lines is the technology of transmitting computer data through power lines. This method of connectivity allows the user to have access to the internet without having to rely on additional cables, suc…
    #Citrix #Citrix Netscaler #HTTP Compression #Load Balance
    To add imagery to an HTML email signature, you have two options available to you. You can either add a logo/image by embedding it directly into the signature or hosting it externally and linking to it. The vast majority of email clients display l…
    Excel styles will make formatting consistent and let you apply and change formatting faster. In this tutorial, you'll learn how to use Excel's built-in styles, how to modify styles, and how to create your own. You'll also learn how to use your custo…

    737 members asked questions and received personalized solutions in the past 7 days.

    Join the community of 500,000 technology professionals and ask your questions.

    Join & Ask a Question

    Need Help in Real-Time?

    Connect with top rated Experts

    20 Experts available now in Live!

    Get 1:1 Help Now