3com S7906E Instruccion De Instalación

 

1-7 

Redirect message 

137 

When a certain condition is satisfied, the default 
gateway sends a redirect message to the source host 
so that the host can reselect a correct next hop router 
to forward packets. 

 

The NDP mainly provides the following functions: 

Similar to the ARP function in IPv4, a node acquires the link-layer addresses of neighbor nodes on the 

same link through NS and NA messages. 

 shows how node A acquires the link-layer address 

of node B. 

Figure 1-3 Address resolution 

 

 

The address resolution procedure is as follows: 

1)  Node A multicasts an NS message. The source address of the NS message is the IPv6 address of 

the sending interface of node A and the destination address is the solicited-node multicast address 

of node B. The NS message contains the link-layer address of node A. 

2)  After receiving the NS message, node B judges whether the destination address of the packet is its 

solicited-node multicast address. If yes, node B learns the link-layer address of node A, and then 

unicasts an NA message containing its link-layer address. 

3)  Node A acquires the link-layer address of node B from the NA message. 

After node A acquires the link-layer address of its neighbor node B, node A can verify whether node B is 

reachable according to NS and NA messages. 

1)  Node A sends an NS message whose destination address is the IPv6 address of node B. 

2)  If node A receives an NA message from node B, node A considers that node B is reachable. 

Otherwise, node B is unreachable. 

After node A acquires an IPv6 address, it will perform duplicate address detection (DAD) to determine 

whether the address is being used by any other node (similar to the gratuitous ARP function of IPv4). 

DAD is accomplished through NS and NA messages. 

 shows the DAD procedure.