Hi every body!
Let say we have ipv6 enabled router r1, r1 has two interface so and f 0.
so has ip address 2340:1111:AAAA :2::1/64
fo has ip address 2340: 1111:AAAA:1::/64 eui-64
S0R1 f 0------------------h2
H2 has ip address 2340:1111:AAA:1: 0234: 56FF:FE78:9ABC
r1 receives a ip packet with destination ip address" 2340:1111:AAA:1: 0234: 56FF:FE78:9ABC" . r1 has no entry in arp cache for h2 's mac address. Will r1 note the " 56FF: FE78" in interface field and conclude this is the mac address for h2 and therefore does not need to send arp request to h2?
2) If i have to use the option of eui-64 to configure ipv6 address on interface, ipv6 sets the 7 bit to 1 to get the modified eui-64 format. My question is why? why can we not use the mac address whose 7 bit is 0?
Thanks a lot!
in ipv6 ICMPv6 includes and extends functions of ICMPv4, ARP, and IGMP.
There are also duplicate address detection and neighbor discovery that are part of ND.
Actually an IPv6 host mantains a table of known gateway, a table of known hosts.
For each host the IPv6 host tracks the reachability: indirectly if a TCP session is active between the two or sending ICMP probes from time to time.
to answer your first question:
an ICMPv6 packet of type NS (type 135) is sent out using a solicited multicast address destination that is a special link local multicast address that includes the less significant 24 bits.
This packet is used to discover the L2 MAC address or R2.
R2 answers provides the necessary information in an ICMPv6 message of type NA neighbor advertisement (type 136).
This reply is sent with a unicast source MAC address and a unicast destination that is that of R1 lan interface.
IPV6 uses no broadcast at all.
At first is difficult to believe that this is possible
see for an explanation:
Once the entry is created the link address is associated to R2:lan interface ipv6 address.
From time to time if not refreshed by routing protocols or TCP sessions R1 can send again messages to confirm that R1 is alive and information is correct
this is somewhat a strange point
in IEEE 48 bits MAC addresses the second bit of the most significant octet is the U/L bit : 0 means universal, 1 means locally administered.
In creating the eui-64 interface identifier they decided in someway to revert this bit: now if the bit is set means a universal identifier.
see also appendix A
Hope to help