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I'm studing on this topic, and I learned that, when a node joins a network, it creates a local unicast address based on his MAC, then send a Neighbor Solicitation message to the multicast neighbor-solicited group of that address for detecting any duplicate. Then it sends a Router Solicitation message, it receives (hopefully) a Router Advertisement message containing the network prefix, and then it create his global unicast address based on this informations. But, as you can see in this screenshot (look at the highlighted packets), my node joins the network and sends the first NS, as described above, and then a second NS with targed address his global unicast address already built, without first sending RS and getting RA with network prefix. Can someone explain how it gets the network prefix? Maybe it collects the RAs that the router was sending before it sends his NS? I hope that someone help my understanding this. Thanks wireshark-capture-address-autoconfiguration

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Alex_DeLarge
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  • It has already received plenty of RAs, but nowhere in there has it sent anything with a source global unicast address. Where do you get "_it create his global unicast address based on this informations?_" – Ron Maupin Nov 07 '22 at 13:31
  • in packet 23 he sends a NS for a global unicast address (2001:760:400:0:5604:a6ff:fe4a:af15). My question is: how did he calculate his address, if he sends a RS in packet 24 and therefore he didn't know network prefix before packet 24? I'm try to explain better: for what I studied, a host that join a network should follow these: - calculate his unicast local address - send a NS for that unicast address (with the multicast solicited nodes address) - send a RS - receive RA with network prefix and calculate his global unicast address. Here, he calculate his global address at step 1 – Alex_DeLarge Nov 07 '22 at 14:59
  • That is a destination address. It could be that an application knows the destination address, and it is trying to get the data-link address for that IPv6 address. That has nothing to do with the host having its own global address. – Ron Maupin Nov 07 '22 at 15:08
  • so you think it's a coincidence? However, i've added the network configuration for that packet capture – Alex_DeLarge Nov 07 '22 at 18:34
  • You are simply asking on the wrong SE site. Your question is not about programming, so it is off-topic here. – Ron Maupin Nov 07 '22 at 18:38
  • I don't know Ron, here we're talking about the algorithm of NDP, and its implementation, that is: when this algorithm collect the variable "network prefix"? I mean, there is a precise moment in which he sets the variable. He collects the previous unsolicited RAs? So this variable "network prefix" is always settable? – Alex_DeLarge Nov 08 '22 at 14:33

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