eui-64 option - I think I got it

From: ccie2be (ccie2be@nyc.rr.com)
Date: Mon Feb 07 2005 - 20:05:24 GMT-3

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Hey guys,

I went back to my Syngress book on ipv6 to see if I could figure out when I
needed to use the eui-64 option

when configuring an ipv6.

Here's my conclusion:

It's optional (unless the lab says otherwise).

If you want - for whatever reasons - to assign all 128 of the address you can
do so.

For example, below the least significant bit (bit 128) is 1.

Rack1R1(config-if)#ipv6 address 2001:157:1:14::1/64
Rack1R1(config-if)#do sh ipv6 int e0/0
Ethernet0/0 is up, line protocol is up
  IPv6 is enabled, link-local address is FE80::2D0:58FF:FE6E:B720
  Global unicast address(es):
    2001:157:1:14::1, subnet is 2001:157:1:14::/64 <-- unicast address
doesn't include mac addr
  Joined group address(es):
    FF02::1
    FF02::2
    FF02::1:FF00:1
    FF02::1:FF6E:B720
  MTU is 1500 bytes
  ICMP error messages limited to one every 100 milliseconds
  ICMP redirects are enabled
  ND DAD is enabled, number of DAD attempts: 1
  ND reachable time is 30000 milliseconds
  ND advertised reachable time is 0 milliseconds
  ND advertised retransmit interval is 0 milliseconds
  ND router advertisements are sent every 200 seconds
  ND router advertisements live for 1800 seconds
  Hosts use stateless autoconfig for addresses.
Rack1R1(config-if)#

However, if I want - for whatever reasons - to have the router assign the
least significant 64 bits,
I could just add the eui-64 option to the end of the address command.

Rack1R1(config-if)#no ipv6 address 2001:157:1:14::1/64 <-- remove previous
address
Rack1R1(config-if)#ipv6 address 2001:157:1:14::/64 eui-64
Rack1R1(config-if)#do sh ipv6 int e0/0
Ethernet0/0 is up, line protocol is up
  IPv6 is enabled, link-local address is FE80::2D0:58FF:FE6E:B720
  Global unicast address(es):
    2001:157:1:14:2D0:58FF:FE6E:B720, subnet is 2001:157:1:14::/64 <--unicast
addr includes mac addr
  Joined group address(es):
    FF02::1
    FF02::2
    FF02::1:FF6E:B720
  MTU is 1500 bytes
  ICMP error messages limited to one every 100 milliseconds
  ICMP redirects are enabled
  ND DAD is enabled, number of DAD attempts: 1
  ND reachable time is 30000 milliseconds
  ND advertised reachable time is 0 milliseconds
  ND advertised retransmit interval is 0 milliseconds
  ND router advertisements are sent every 200 seconds
  ND router advertisements live for 1800 seconds
  Hosts use stateless autoconfig for addresses.
Rack1R1(config-if)#

Do I have this right?

Thanks for all your feedback. Tim

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