I have a little embedded device directly connected to a laptop via a crossover cable. I'm monitoring the traffic between the two using Wireshark and I witness a TTL of 30 for TCP packets coming from the device (when they reach the laptop).

What is the device's initial TTL? I'm thinking it could either 30 or 32?

I guess my question is does the hop count decrease over a cross over (I suspect it does but not sure)?

1 Answer 1


Unless there is forwarding going on prior to delivery (i.e. the laptop has two interfaces and it crosses between them because its destination is not the port it came in on) then the TTL should not be altered. The source can set a TTL of whatever it likes up to a maximum of 255, and if you are watching it arrive from the device with a TTL of 30 and it only traversed a patch cable, then it quite certainly started with 30.

  • 4
    Routers decrement, bridges do not. The cable definitely isn't.
    – Ricky
    Commented Jun 9, 2015 at 20:14

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