Solved: ipv6 and stateful dhcp

sarahr202 · ‎04-08-2009

Hi every body!

If a host is configured to obtain ipv6 address from dhcp server, will it use link local address to request the ipv6 address, dns ip, default gateway address from dhco server?

My book shows:

FD00::/8 unique local address

FE80::/10 link-local address

My question is what is unique local address and what its purpose ?

==========================

int f0

ip v6 address 2001:1111:AAAA:1::/64 eui-64

If the f0 has mac address 2111:32FF: FE22:2222

then first 8 bits from left to right would be

0010=2

0001=1

0r 0000 0001

Now the ipv6 host will set the 7 th bit from left to right to 1. Therefore

0010 0011

So eui-64 format will be 2311:32FF: FE22:2222

so the ipv6 address would be:

2001:1111:AAAA:1:2311:32FF: FE22:2222

How about link-local address? will hostipv6 use the eui-64 format i.e 2311:32FF: FE22:2222

where the 7 bit from left to right is set 1 or simply use the original mac address i.e

2111:32FF: FE22:2222 ?

thanks a lot!

Giuseppe Larosa · ‎04-08-2009

Hello Sarah,

Unique local addresses are the evolution of site local addresses.

They are like RFC 1918 private ip addresses.

They can be routed but they are not public.

see

http://tools.ietf.org/html/rfc4193

b) each activity involves the usage of link local addresses so ICMPv6 messages need to use link local and also DHCP related messages.

see for example

http://www.cisco.com/en/US/docs/ios/ipv6/configuration/guide/ip6-dhcp.html#wp1055654

c) also link local uses eui-64:

http://www.cisco.com/en/US/docs/ios/ipv6/configuration/guide/ip6-addrg_bsc_con.html#wp1038809

A link-local address is an IPv6 unicast address that can be automatically configured on any interface using the link-local prefix FE80::/10 (1111 1110 10) and the interface identifier in the modified EUI-64 format.

Hope to help

Giuseppe

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Giuseppe Larosa · ‎04-08-2009