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The BSCI examination and CCNP accreditation requires that you be well versed in the basic principles of Internet Protocol Address Version 6, or IPv6. If you are new to IPv6, you'll quickly learn it is not exactly just two more octets slapped onto an IPv4 handle! IPv6 addresses are quite long, but there are two approaches to acceptably limit IPv6 target term. To turn into a CCNP, pass the BSCI test, and get that all-important knowledge of IPv6, you've got to comprehend these different methods of expressing an IPv6 address. My last IPv6 article discussed zero compression; today we'll take a look at leading zero pressure. 

Leading zero compression allows us to drop the leading zeroes out of each and every subject in the handle. Leading zero compression can be used normally as is acceptable, where we will only use zero compression once in an IPv6 address expression. The important thing with leading zero pressure is that there should be at least one number left in each field, even though that remaining number is really a zero. 

You sometimes see books or websites refer to primary zero pressure as "dropping zeroes and replacing them with a, but since the blocks are separated with a colon to start with, that reason could be a little complicated. You're certainly not replacing the best zeroes, you are dropping them.  [http://www.youtube.com/watch?v=J5osbPIn6uQ site]

Let us look at a good example of leading zero compression. Taking the address 1234:0000:1234:0000:1234:0000:1234:0123, we've four different areas that have leading zeroes. The handle could possibly be written out since it is, or drop the best zeroes. 

Original format: 1234:0000:1234:0000:1234:0000:0123:1234 

With leading zero compression: 1234:0:1234:0:1234:0:123:1234 

There's no issue with applying zero compression and major zero compression in the exact same handle, as shown here: 

Original format: 1111:0000:0000:1234:0011:0022:0033:0044 

With zero and leading zero compression: 1111::1234:11:22:33:44 

Zero compression uses the double-colon to restore the 2nd and third block of numbers, that have been all zeroes; leading zero compression exchanged the "00" at the beginning of each of the past four blocks. You should be careful and take your time with equally zero compression and major zero compression and you'll do well on the exam and in actuality. The keys to success listed below are remembering that you can only use zero compression once in a single handle, and that while major zero compression can be properly used as often as needed, one or more number should stay in each field, even though that number is just a zero.