Tuesday, July 15, 2008

IPv6 - link local address, MAC to EUI-64 conversion

The fastest way to get a link local address is to configure an interface with the ipv6 enable command. For example:

R1(config)#int f0/0
R1(config-if)#ipv6 enable

What will the link local address be? Before we take a look, let's figure it out ourselves. First do a show interface:

R1#show int f0/0 | in add
Hardware is Gt96k FE, address is c200.0854.0000 (bia c200.0854.0000)

To convert this MAC address to a link-local using eui-64 format do the following:

1. MAC Address: c200.0854.0000
2. Insert FFFE in the middle: c200:08FF:FE54:0000
3 Flip the U/L bit: 7th bit from the left: c000:08FF:FE54:0000
4. Append the prefix FE80: FE80::c000:08FF:FE54:0000
5. Remove extra 0's: FE80::C000:8FF:FE54:0

Let's take a look:

R1#show ipv6 interface f0/0 | in link
IPv6 is enabled, link-local address is FE80::C000:8FF:FE54:0


  1. This is usefl bt can Ihave some more links to learn IPv6 ?

  2. That guy's keyboard is broken. Or he's asking for help without expending even the effort to fully type complete words.


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