Atmel AVR2070 User Manual

 

8240B-AVR-06/09 

 

On power-up a node uses these packets to acquire an address using stateless auto-
configuration. It first auto-configures a link-local address by using the fe80:: prefix 
followed by an interface identifier description (IID) based on its physical address. It 
then sends a neighbor solicitation packet looking for someone else with this same 
address – this is the duplicate address detection (DAD) phase. If no response is 
heard to the neighbor solicitation, it assumes it has a valid unique address. A router 
solicitation is then sent out to learn about any on-link routers. If the routers have prefix 
information, it can then combine the network prefix with the IID to form a globally 
accessible address.  

As an example, consider how an Ethernet interface with a physical address of 
00:1C:23:2B:BD:6C gets a fully operational address: 

1.  Node comes to life, calculates an IID of 021c:23ff:fe2b:bd6c/64 from its 

physical address. 

2.  Node sends a neighbor solicitation to fe80::21c:23ff:fe2b:bd6c. 

3.  Node waits for response, resending neighbor solicitation a certain number of 

times. 

4.  Node fails to hear a response, so auto-configures itself to have the address 

fe80::21c:23ff:fe2b:bd6c. 

5. Node sends a neighbor advertisement, advertising it has address 

fe80::21c:23ff:fe2b:bd6c. 

6.  Node sends a router solicitation. 

7.  Router sends a router advertisement, out of which node finds the network 

prefix is 2001:db8:1e1::/64. 

8.  Node sends neighbor solicitation to 2001:db8:1e1:0:21c:23ff:fe2b:bd6c, again 

listening for a response. 

9. No response heard, node advertises itself as owning address 

2001:db8:1e1:0:21c:23ff:fe2b:bd6c.