This is from IPexpert volume 1 section 22. We have to summarize the following routes:

2020:100:100:2222::/64

2020:100:100:2666::/64

This is how I do it:

1) Identify the hextet ( I don't know if this is a word, I derived it from octet) where we will summarize. This is the 4th hextet. So we know our subnet will be somewhere between /48 and /64.

2) Break it down in binary:

2222 = 0010 0010 0010 0010

2666 = 0010 0110 0110 0110

Converting hex to binary is easy because we just treat each digit in the IPv6 address as a 4 bit binary number by itself. Notice how all the 2's broke down to 0010.

3) Find the common bits. I highlighted them in red below. We have 5 of them. We will use to get our mask.

2222 = 0010 0010 0010 0010

2666 = 0010 0110 0110 0110

4) Set the rest if the bits to 0 and calculate the summary, convert to hex.

summary = 0010 0000 0000 0000 = 2000

5) Calculate subnet mask by adding the common bits to the lower of our subnet range. This means we add 5 to /48 which makes /53.

So our summary address is 2020:100:100:2000::/53

In OSPFv3 we would enter:

R2(config)#ipv6 router ospf 1

R2(config-rtr)#area 1 range 2020:100:100:2000::/53

Check our other routers for the summary:

R4#show ipv6 route | inc 53

OI 2020:100:100:2000::/53 [110/129]

## Tuesday, September 23, 2008

Subscribe to:
Post Comments (Atom)

Hey,

ReplyDeleteI know the post is more than two years old, but it has been very useful to me. IPv6 summarization is quite different from IPv4. Thanks for the clarifying post :D

Just ran across this .. thanks! I was studying ipv6 today and I totaly hit a roadblock and was overthinking this

ReplyDeleteThis comment has been removed by the author.

ReplyDelete