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ICND2 – IP Routing 2

October 15th, 2017 in ICND2 200-105 Go to comments

[am4show have=’p2;’]

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Question 1

[am4show have=’p2;’]Refer to the exhibit, Host A pings interface S0/0 on router 3, what is the TTL value for that ping?

TTL_ping.jpg

A. 253
B. 252
C. 255
D. 254

 

Answer: A[/am4show]

Explanation

From the CCNA ICND2 Exam book: “Routers decrement the TTL by 1 every time they forward a packet; if a router decrements the TTL to 0, it throws away the packet. This prevents packets from rotating forever.” I want to make it clear that before the router forwards a packet, the TTL is still remain the same. For example in the topology above, pings to S0/1 and S0/0 of Router 2 have the same TTL.

The picture below shows TTL values for each interface of each router and for Host B. Notice that Host A initializes ICMP packet with a TTL of 255:

TTL_ping_detail.jpg

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