IPv6 : Hop Limit field with traceroute6

ICMPv6, described in the IPv6 chapter of Computer Networking: Principles, Protocols and Practice is a companion protocol for IPv6 that is used for various functions including network debugging. traceroute6 is a popular debugging tool that allows to trace the path towards a destination.

Paste this command into your terminal:

The password to connect is

Usage of Hop Limit by traceroute6

Can you infer the Hop Limit value of the packets captured during the following traceroute6:

traceroute6 -q 1 -n www.ietf.org
traceroute6: Warning: www.ietf.org.cdn.cloudflare.net has multiple addresses; using 2606:4700:10::6814:155
traceroute6 to www.ietf.org.cdn.cloudflare.net (2606:4700:10::6814:155) from 2a02:2788:484:59e:2c1c:849e:f74f:e233, 64 hops max, 12 byte packets
1  2a02:2788:484:59e:a221:b7ff:fed8:aa90  2.415 ms
2  2a02:2788:480::1  8.138 ms
3  2a02:2788:480:2::1  9.125 ms
4  2a02:2788:ffff:1b::1  9.757 ms
5  2001:7f8:26::a501:3335:1  7.960 ms
6  2400:cb00:78:1024::a29e:e959  7.934 ms

#	Length	Summary
0	48 bytes	`User Datagram Protocol, Src Port: 53634, Dst Port: 33435`
1	48 bytes	`User Datagram Protocol, Src Port: 53634, Dst Port: 33436`
2	48 bytes	`User Datagram Protocol, Src Port: 53634, Dst Port: 33437`
3	48 bytes	`User Datagram Protocol, Src Port: 53634, Dst Port: 33438`
4	48 bytes	`User Datagram Protocol, Src Port: 53634, Dst Port: 33439`
5	48 bytes	`User Datagram Protocol, Src Port: 53634, Dst Port: 33440`

0000  6007d0ed001411??  2a0227880484059e
0010  2c1c849ef74fe233  2606470000100000
0020  0000000068140155  d182829b00141a84

0000  `.Ðí...?*.'.....
0010  ,...÷Oâ3&.G.....
0020  ....h..UÑ.......

Internet Protocol Version 6, Src: 2a02:2788:484:59e:2c1c:849e:f74f:e233, Dst: 2606:4700:10::6814:155
- 0110 .... = Version: 6
- .... 0000 0000 .... .... .... .... .... = Traffic Class: 0x00 (DSCP: CS0, ECN: Not-ECT)
  - .... 0000 00.. .... .... .... .... .... = Differentiated Services Codepoint: Default (0)
  - .... .... ..00 .... .... .... .... .... = Explicit Congestion Notification: Not ECN-Capable Transport (0)
- .... .... .... 0111 1101 0000 1110 1101 = Flow Label: 0x7d0ed
- Payload Length: 20
- Next Header: UDP (17)
- Hop Limit: ?
- Source: 2a02:2788:484:59e:2c1c:849e:f74f:e233
- Destination: 2606:4700:10::6814:155
User Datagram Protocol, Src Port: 53634, Dst Port: 33435
- Source Port: 53634
- Destination Port: 33435
- Length: 20
- Checksum: 0x1a84 [unverified]

0000  6007d0ed001411??  2a0227880484059e
0010  2c1c849ef74fe233  2606470000100000
0020  0000000068140155  d182829c00141170

0000  `.Ðí...?*.'.....
0010  ,...÷Oâ3&.G.....
0020  ....h..UÑ......p

Internet Protocol Version 6, Src: 2a02:2788:484:59e:2c1c:849e:f74f:e233, Dst: 2606:4700:10::6814:155
- 0110 .... = Version: 6
- .... 0000 0000 .... .... .... .... .... = Traffic Class: 0x00 (DSCP: CS0, ECN: Not-ECT)
  - .... 0000 00.. .... .... .... .... .... = Differentiated Services Codepoint: Default (0)
  - .... .... ..00 .... .... .... .... .... = Explicit Congestion Notification: Not ECN-Capable Transport (0)
- .... .... .... 0111 1101 0000 1110 1101 = Flow Label: 0x7d0ed
- Payload Length: 20
- Next Header: UDP (17)
- Hop Limit: ?
- Source: 2a02:2788:484:59e:2c1c:849e:f74f:e233
- Destination: 2606:4700:10::6814:155
User Datagram Protocol, Src Port: 53634, Dst Port: 33436
- Source Port: 53634
- Destination Port: 33436
- Length: 20
- Checksum: 0x1170 [unverified]

0000  6007d0ed001411??  2a0227880484059e
0010  2c1c849ef74fe233  2606470000100000
0020  0000000068140155  d182829d0014f0b3

0000  `.Ðí...?*.'.....
0010  ,...÷Oâ3&.G.....
0020  ....h..UÑ.....ð³

Internet Protocol Version 6, Src: 2a02:2788:484:59e:2c1c:849e:f74f:e233, Dst: 2606:4700:10::6814:155
- 0110 .... = Version: 6
- .... 0000 0000 .... .... .... .... .... = Traffic Class: 0x00 (DSCP: CS0, ECN: Not-ECT)
  - .... 0000 00.. .... .... .... .... .... = Differentiated Services Codepoint: Default (0)
  - .... .... ..00 .... .... .... .... .... = Explicit Congestion Notification: Not ECN-Capable Transport (0)
- .... .... .... 0111 1101 0000 1110 1101 = Flow Label: 0x7d0ed
- Payload Length: 20
- Next Header: UDP (17)
- Hop Limit: ?
- Source: 2a02:2788:484:59e:2c1c:849e:f74f:e233
- Destination: 2606:4700:10::6814:155
User Datagram Protocol, Src Port: 53634, Dst Port: 33437
- Source Port: 53634
- Destination Port: 33437
- Length: 20
- Checksum: 0xf0b3 [unverified]

0000  6007d0ed001411??  2a0227880484059e
0010  2c1c849ef74fe233  2606470000100000
0020  0000000068140155  d182829e0014cd01

0000  `.Ðí...?*.'.....
0010  ,...÷Oâ3&.G.....
0020  ....h..UÑ.....Í.

Internet Protocol Version 6, Src: 2a02:2788:484:59e:2c1c:849e:f74f:e233, Dst: 2606:4700:10::6814:155
- 0110 .... = Version: 6
- .... 0000 0000 .... .... .... .... .... = Traffic Class: 0x00 (DSCP: CS0, ECN: Not-ECT)
  - .... 0000 00.. .... .... .... .... .... = Differentiated Services Codepoint: Default (0)
  - .... .... ..00 .... .... .... .... .... = Explicit Congestion Notification: Not ECN-Capable Transport (0)
- .... .... .... 0111 1101 0000 1110 1101 = Flow Label: 0x7d0ed
- Payload Length: 20
- Next Header: UDP (17)
- Hop Limit: ?
- Source: 2a02:2788:484:59e:2c1c:849e:f74f:e233
- Destination: 2606:4700:10::6814:155
User Datagram Protocol, Src Port: 53634, Dst Port: 33438
- Source Port: 53634
- Destination Port: 33438
- Length: 20
- Checksum: 0xcd01 [unverified]

0000  6007d0ed001411??  2a0227880484059e
0010  2c1c849ef74fe233  2606470000100000
0020  0000000068140155  d182829f0014acdc

0000  `.Ðí...?*.'.....
0010  ,...÷Oâ3&.G.....
0020  ....h..UÑ.....¬Ü

Internet Protocol Version 6, Src: 2a02:2788:484:59e:2c1c:849e:f74f:e233, Dst: 2606:4700:10::6814:155
- 0110 .... = Version: 6
- .... 0000 0000 .... .... .... .... .... = Traffic Class: 0x00 (DSCP: CS0, ECN: Not-ECT)
  - .... 0000 00.. .... .... .... .... .... = Differentiated Services Codepoint: Default (0)
  - .... .... ..00 .... .... .... .... .... = Explicit Congestion Notification: Not ECN-Capable Transport (0)
- .... .... .... 0111 1101 0000 1110 1101 = Flow Label: 0x7d0ed
- Payload Length: 20
- Next Header: UDP (17)
- Hop Limit: ?
- Source: 2a02:2788:484:59e:2c1c:849e:f74f:e233
- Destination: 2606:4700:10::6814:155
User Datagram Protocol, Src Port: 53634, Dst Port: 33439
- Source Port: 53634
- Destination Port: 33439
- Length: 20
- Checksum: 0xacdc [unverified]

0000  6007d0ed001411??  2a0227880484059e
0010  2c1c849ef74fe233  2606470000100000
0020  0000000068140155  d18282a000148b22

0000  `.Ðí...?*.'.....
0010  ,...÷Oâ3&.G.....
0020  ....h..UÑ......"

Internet Protocol Version 6, Src: 2a02:2788:484:59e:2c1c:849e:f74f:e233, Dst: 2606:4700:10::6814:155
- 0110 .... = Version: 6
- .... 0000 0000 .... .... .... .... .... = Traffic Class: 0x00 (DSCP: CS0, ECN: Not-ECT)
  - .... 0000 00.. .... .... .... .... .... = Differentiated Services Codepoint: Default (0)
  - .... .... ..00 .... .... .... .... .... = Explicit Congestion Notification: Not ECN-Capable Transport (0)
- .... .... .... 0111 1101 0000 1110 1101 = Flow Label: 0x7d0ed
- Payload Length: 20
- Next Header: UDP (17)
- Hop Limit: ?
- Source: 2a02:2788:484:59e:2c1c:849e:f74f:e233
- Destination: 2606:4700:10::6814:155
User Datagram Protocol, Src Port: 53634, Dst Port: 33440
- Source Port: 53634
- Destination Port: 33440
- Length: 20
- Checksum: 0x8b22 [unverified]

Author(s)	Olivier Bonaventure
Deadline	No deadline
Submission limit	No limitation
Category tags	ipv6

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