CCIE Pursuit Blog

April 1, 2008

Question Of The Day: 01 April, 2008

Topic: IPv6

FastEthernet0/0 is up, line protocol is up
  Hardware is AmdFE, address is cc01.17b4.0000 (bia cc01.17b4.0000)
  Internet address is

r2(config)#ipv6 unicast-routing
r2(config)#int fa0/0
r2(config-if)#ipv6 enable

What will be the IPv6 address of interface fa0/0?

Click Here For Answer

Yesterday’s Question

Question Of The Day: 31 March, 2008 

Topic: IPv6

FastEthernet0/0 is up, line protocol is up
  Hardware is AmdFE, address is cc00.17b4.0000 (bia cc00.17b4.0000)
  Internet address is

r1(config)#ipv6 unicast-routing
r1(config)#int fa0/0
r1(config-if)#ipv6 address 2001:B00B:1E5:1::/64 eui-64

What will r1’s fao/o IPv6 address be after this configuration is applied?

Answer: 2001:B00B:1E5:1:CE00:17FF:FEB4:0

The (modified) IPv6 eui-address is derived from the interface’s MAC Address with the following method:

Step 1 – Invert the seventh most significant bit of the MAC address.

This requires us to do some quick and dirty hexadecimal to binary conversion.  Luckily each hex character represents 4 bits, so we only need to convert the first two hex characters of the MAC address to include the seventh most significant bit:

cc = 1100 1100

Now let’s flip that seventh bit

1100 1110

Finally let’s convert this back to hex:

1100 1110 = ce

Step 2 – Split the MAC address in half and insert ‘fffe’

ce00.17 | b4.0000

Voila!  Now our 48-bit MAC address has been converted to 64-bits.  We just need to combine it with the IPv6 network portion and we will have our eui-64 IPv6 address:


r1#sh ipv6 int br | sec net0/0
FastEthernet0/0            [up/up]


1 Comment »

  1. […] Click Here For Answer […]

    Pingback by Question Of The Day: 31 March, 2008 « CCIE Pursuit — April 2, 2008 @ 10:22 am | Reply

RSS feed for comments on this post. TrackBack URI

Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Google+ photo

You are commenting using your Google+ account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )


Connecting to %s

Create a free website or blog at

%d bloggers like this: