Shortened Expression
The good news is there are a few tricks to help rescue us when writing these monster addresses.
For one thing, you can actually omit parts of the address to abbreviate it, but to get away with
doing that you have to follow a couple of rules. First, you can drop any leading zeros in each
of the individual blocks. After you do that, the sample address from earlier would then look
like this:
2001:db8:3c4d:12:0:0:1234:56ab
OK, that’s a definite improvement—at least we don’t have to write all of those extra zeros!
But what about whole blocks that don’t have anything in them except zeros? Well, we can
kind of lose those too—at least some of them. Again referring to our sample address, we can
remove the two blocks of zeros by replacing them with double colons, like this:
2001:db8:3c4d:12::1234:56ab
Cool—we replaced the blocks of all zeros with double colons. The rule you have to follow
to get away with this is that you can replace only one contiguous block of zeros in an address.
So if my address has four blocks of zeros and each of them were separated, I just don’t get to
replace them all. Check out this example:
2001:0000:0000:0012:0000:0000:1234:56ab
And just know that you
can’t
do this:
2001::12::1234:56ab
Instead, this is the best you can do:
2001::12:0:0:1234:56ab
The reason why the previous example is your best shot is that if you remove two sets of
zeros, the device looking at the address will have no way of knowing where the zeros go back
in. Basically, the router would look at the incorrect address and say, “Well, do I place two
blocks into the first set of double colons and two into the second set, or do I place three blocks
into the first set and one block into the second set?” And on and on it would go because the
information the router needs just isn’t there.
IT Certification CCIE,CCNP,CCIP,CCNA,CCSP,Cisco Network Optimization and Security Tips
IPv6 Addressing and Expressions
IPv6 Addressing and Expressions
Just as understanding how IP addresses are structured and used is critical with IPv4 addressing,
it’s also vital when it comes to IPv6. You already know that at 128 bits, an IPv6 address is
much larger than an IPv4 address. Because of this, as well as the new ways the addresses can
be used, you’ve probably guessed that IPv6 will be more complicated to manage. But no worries!
As I said, I’ll break down the basics and show you what the address looks like, how you
can write it, and what many of its common uses are. It’s going to be a little weird at first, but
before you know it, you’ll have it nailed!
So let’s take a look at Figure 10.1, which has a sample IPv6 address broken down into
sections.
FIGURE 1 0 . 1
IPv6 address example
So as you can now see, the address is truly much larger—but what else is different? Well,
first, notice that it has eight groups of numbers instead of four and also that those groups are
separated by colons instead of periods. And, hey, wait a second…there are letters in that
address! Yep, the address is expressed in hexadecimal just like a MAC address is, so you could
say this address has eight 16-bit hexadecimal colon-delimited blocks. That’s already quite a
mouthful, and you probably haven’t even tried to say the address out loud yet!
When you use a web browser to make an HTTP connection to an IPv6 device, you have to
type the address into the browser with brackets around the literal address. Why? Well, the
browser is already using a colon for specifying a port number. So basically, if you don’t enclose
the address in brackets, the browser will have no way to identify the information.
Here’s an example of how this looks:
http://[2001:0db8:3c4d:0012:0000:0000:1234:56ab]/default.html
Now obviously, if you can, you would rather use names to specify a destination (such as
www.lammle.com
). However, even though it’s definitely going to be a pain in the rear, we just
have to accept the fact that sometimes we have to type the address number. So, it should be
pretty clear that DNS is going to become extremely important when implementing IPv6.
Just as understanding how IP addresses are structured and used is critical with IPv4 addressing,
it’s also vital when it comes to IPv6. You already know that at 128 bits, an IPv6 address is
much larger than an IPv4 address. Because of this, as well as the new ways the addresses can
be used, you’ve probably guessed that IPv6 will be more complicated to manage. But no worries!
As I said, I’ll break down the basics and show you what the address looks like, how you
can write it, and what many of its common uses are. It’s going to be a little weird at first, but
before you know it, you’ll have it nailed!
So let’s take a look at Figure 10.1, which has a sample IPv6 address broken down into
sections.
FIGURE 1 0 . 1
IPv6 address example
So as you can now see, the address is truly much larger—but what else is different? Well,
first, notice that it has eight groups of numbers instead of four and also that those groups are
separated by colons instead of periods. And, hey, wait a second…there are letters in that
address! Yep, the address is expressed in hexadecimal just like a MAC address is, so you could
say this address has eight 16-bit hexadecimal colon-delimited blocks. That’s already quite a
mouthful, and you probably haven’t even tried to say the address out loud yet!
When you use a web browser to make an HTTP connection to an IPv6 device, you have to
type the address into the browser with brackets around the literal address. Why? Well, the
browser is already using a colon for specifying a port number. So basically, if you don’t enclose
the address in brackets, the browser will have no way to identify the information.
Here’s an example of how this looks:
http://[2001:0db8:3c4d:0012:0000:0000:1234:56ab]/default.html
Now obviously, if you can, you would rather use names to specify a destination (such as
www.lammle.com
). However, even though it’s definitely going to be a pain in the rear, we just
have to accept the fact that sometimes we have to type the address number. So, it should be
pretty clear that DNS is going to become extremely important when implementing IPv6.
Why Do We Need IPv6?
Why Do We Need IPv6?
Well, the short answer is, we need to communicate, and our current system isn’t really cutting
it anymore—kind of like how the Pony Express can’t compete with airmail. Just look at how
much time and effort we’ve invested in coming up with slick new ways to conserve bandwidth
and IP addresses. We’ve even come up with variable-length subnet masks (VLSMs) in our
struggle to overcome the worsening address drought.
It’s reality—the amount of people and devices that connect to networks increases every day.
That’s not a bad thing at all—we’re finding new and exciting ways to communicate to more
people all the time, and that’s a good thing. In fact, it’s a basic human need. But the forecast
isn’t exactly blue skies and sunshine because IPv4, upon which our ability to communicate is
currently dependent, is going to run out of addresses for us to use. IPv4 has only about 4.3 billion
addresses available—that’s in theory, and we know that we don’t even get to use all of
those. There really are only about 250 million addresses that can be assigned to devices. Sure,
Classless Inter-Domain Routing (CIDR) and Network Address Translation (NAT) have helped
to extend the inevitable dearth of addresses, but we will run out of them, and it’s going to
happen within a few years. China is barely online, and we know there’s a huge population of
people and corporations there that surely want to be. Many reports give us all kinds of
numbers, but all you really need to think about to convince yourself that I’m not just being an
alarmist is the fact that there are about 6.5 billion people in the world today, and it’s estimated
that just more than 10 percent of that population is connected to the Internet—wow!
That statistic is basically screaming at us the ugly truth that, based on IPv4’s capacity, every
person can’t even have a computer—let alone all the other devices we use with them. I have
more than one computer, and it’s pretty likely you do too. And I’m not even including in the
mix phones, laptops, game consoles, fax machines, routers, switches, and a mother lode of
other devices we use every day! So I think I’ve made it pretty clear that we have to do something
before we run out of addresses and lose the ability to connect with each other as we
know it. And that “something” just happens to be implementing IPv6.
Well, the short answer is, we need to communicate, and our current system isn’t really cutting
it anymore—kind of like how the Pony Express can’t compete with airmail. Just look at how
much time and effort we’ve invested in coming up with slick new ways to conserve bandwidth
and IP addresses. We’ve even come up with variable-length subnet masks (VLSMs) in our
struggle to overcome the worsening address drought.
It’s reality—the amount of people and devices that connect to networks increases every day.
That’s not a bad thing at all—we’re finding new and exciting ways to communicate to more
people all the time, and that’s a good thing. In fact, it’s a basic human need. But the forecast
isn’t exactly blue skies and sunshine because IPv4, upon which our ability to communicate is
currently dependent, is going to run out of addresses for us to use. IPv4 has only about 4.3 billion
addresses available—that’s in theory, and we know that we don’t even get to use all of
those. There really are only about 250 million addresses that can be assigned to devices. Sure,
Classless Inter-Domain Routing (CIDR) and Network Address Translation (NAT) have helped
to extend the inevitable dearth of addresses, but we will run out of them, and it’s going to
happen within a few years. China is barely online, and we know there’s a huge population of
people and corporations there that surely want to be. Many reports give us all kinds of
numbers, but all you really need to think about to convince yourself that I’m not just being an
alarmist is the fact that there are about 6.5 billion people in the world today, and it’s estimated
that just more than 10 percent of that population is connected to the Internet—wow!
That statistic is basically screaming at us the ugly truth that, based on IPv4’s capacity, every
person can’t even have a computer—let alone all the other devices we use with them. I have
more than one computer, and it’s pretty likely you do too. And I’m not even including in the
mix phones, laptops, game consoles, fax machines, routers, switches, and a mother lode of
other devices we use every day! So I think I’ve made it pretty clear that we have to do something
before we run out of addresses and lose the ability to connect with each other as we
know it. And that “something” just happens to be implementing IPv6.
Internet Protocol Version 6 (IPv6)
Internet Protocol
Version 6 (IPv6)
People refer to IPv6 as the “next-generation Internet protocol,”
and it was originally created as the answer to IPv4’s inevitable,
looming address-exhaustion crisis. Though you’ve probably
heard a thing or two about IPv6 already, it has been improved even further in the quest to bring
you the flexibility, efficiency, capability, and optimized functionality that can truly meet your
ever-increasing needs. The capacity of its predecessor, IPv4, pales in comparison—and that’s
the reason it will eventually fade into history completely.
The IPv6 header and address structure has been completely overhauled, and many of the
features that were basically just afterthoughts and addendums in IPv4 are now included as
full-blown standards in IPv6. It’s seriously well equipped, poised, and ready to manage the
mind-blowing demands of the Internet to come.
Version 6 (IPv6)
People refer to IPv6 as the “next-generation Internet protocol,”
and it was originally created as the answer to IPv4’s inevitable,
looming address-exhaustion crisis. Though you’ve probably
heard a thing or two about IPv6 already, it has been improved even further in the quest to bring
you the flexibility, efficiency, capability, and optimized functionality that can truly meet your
ever-increasing needs. The capacity of its predecessor, IPv4, pales in comparison—and that’s
the reason it will eventually fade into history completely.
The IPv6 header and address structure has been completely overhauled, and many of the
features that were basically just afterthoughts and addendums in IPv4 are now included as
full-blown standards in IPv6. It’s seriously well equipped, poised, and ready to manage the
mind-blowing demands of the Internet to come.
Configuring Cisco Wireless Using the SDM/HTTP 220
Configuring Cisco Wireless
Using the SDM/HTTP
Configuring through the SDM is absolutely the easiest way to go for wireless configurations.
Basically, all you charge to do to accompany up an admission point is to aloof about-face it on. But if you do have
a wireless agenda in your router, you’ll charge to configure it aloof as I showed you in the previous
section.
This is my router assuming that I can configure the wireless agenda I accept installed in aperture 3:
There absolutely isn’t too abundant you can do from aural SDM itself, but if I were to bang the Edit
Interface/Connection tab and again bang Summary, I could accredit and attenuate the interface, as well
as bang the Edit button, which would acquiesce me to add NAT, admission lists, and so on, to the interface:
From either the Create Connection awning apparent beforehand or the awning that appears back you click
the Edit button of the additional screen, you can bang Launch Wireless Application. This will accessible a
new HTTP awning that your wireless accessory is configured from alleged the Express Set-up screen.
This is the aforementioned awning you would see if you aloof typed HTTP into an admission point—one like
my 1242AP. The SDM will be acclimated with wireless interfaces for monitoring, for accouterment statistics,
and for accepting admission into the wireless agreement approach on a router that has wireless
interfaces. This is so we don’t accept to use the CLI for the adamantine configurations.
Again, you can configure alone some basal advice from here. But from the abutting screen,
Wireless Express Security, you can configure the wireless AP in either bridging approach or routing
mode—a absolutely air-conditioned feature!
The abutting awning shows the wireless interfaces and the basal settings:
This is the additional allotment of the Wireless Interfaces screen:
Under the Wireless Aegis branch is absolutely area HTTP administration shines! You can
configure encryption, add SSIDs, and configure your RADIUS server settings.
Now, if you were to aloof HTTP in to the 1242AG AP, you’ll see this screen:
This looks amazingly like the APs you’ll acquisition in your ISR routers, and you can configure the
same accessories and aegis too.
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