what I will do is remove the static route that we have on router 2 right now.
And we want to see a fully specified route in action
We’ve seen the first two of our three regular types where we have recursive which is going to specify the next hop IP address and then directly connected which specifies the local router exit interface.
Now we’re going to write a fully specified route and that’s going to include both of those values.
I did run show IPv6 route’s static just to make sure my delete went through
It did, so we can write this one. Let’s go ahead and start with conf t.
By using the “up arrow” on a keyboard, we’ll bring the original route back up
We’ve got the IPv6 route command from earlier and we know that our fully specified route is going to include the local exit interface and the next hop IP address.
So all we’d have to do is have this and I could just tack the extra interface onto the end right?
Wrong!
You have to watch your order here actually because you can’t put the local exit interface on the end of this command because there’s no option there!
So what we need to do is go to the middle of this and put in our interface (or local router exit interface) and now I’ve got IPV6 route, destination prefix, local router exit interface, next hop IP address, and that’s it.
So let’s have a look and see how that looks in the routing table (probably pretty much the same as the other).
You see both a next hop IP address and a local exit interface… Let’s go ahead and ping R4:
everything’s gold and that’s just another way to write the route.
When we went over the IP route command for Version 4, we saw how to end it with the local router exit interface or with the next hop IP address and you will probably develop a preference of your own.
And of course, for the exam we need to know all three.
Did you notice ‘administrative distance’ ? (three pictures later)
We’ll write a floating static route later but I want to show you the syntax of it.
Frankly all you’re doing is putting a number on the end of this command or the end of any static route.
OK let’s just take it off and then put one back on.
No matching routes of the lead !! because the interface is not in the middle of it…
That route is now off. And if I wanted to rewrite it as a floating static route I needed to give it an administrative distance (for example 121)
And there it is you’ll see this in action later. But I wanted to show you that syntax.
Using The Link-Local Address With Static Routes
We’re getting ready to put the link local address to work here in our static route and we’re going to work on R2. I took everything off from previous section as far as a static route went and run show IPV6 route status to verify that.
Still gives you the code table, but it also shows that we don’t have any static routes…
we’re going to use the link local address from R3
The first thing you’ve got to make sure of, is that you grab the right link local address because we have two ethernet interfaces involved in this lab and they’re both going to have their own link local addresses.
So by a quick look at the diagram, R2 is on the same subnet with R3 (2001:2222:3333:1) and that’s the fast Ethernet 0/0 interface. So let’s go over R3 and copy that information:
I’ll copy the link-local address and will paste after I go to R2:
We’re getting invalid input but it’s pointing at a blank space. So it looks like where we should have something else on there. What did I forget?
We need that double colon at the end of that 64 at the end of this address before the 64.
A quick recap: When using a global unicast address as the next-hop in an IPV6 static route, you have the option of adding the local exit interface, and it’s just that- an option.
When using a link-local address as that next-hop, the router will let you know that a local exit interface must be specified. The exam may not be as kind, so it’s a good thing to remember.
So we’ve got to squeeze fast 0/0 right here in the middle and there’s our command… and then we’ll have a look at the static routes
You see ‘via’… But instead of the global address that we’ve had before we’re using the link local address fast ethernet 0/0 or the local exit interface. And the proof is always in the pinging:
Default and Host Static Routes
I’ve taken everything off from previous sections and run ‘show ipv6 route static’ just to make sure we didn’t miss anything:
Let’s go and write a default route:
We’ve been using a prefix there in the middle. But now we’re going to use the two extremes (0 and 128). The zero is going to be used for the default route, and the 128 for the host route (128 zeros represented by two colons )
You’re going to put either local exit interface or the IP BV6 address next-hop at the end here on R2. (Since this is the only interface we’re using, we use fast ethernet 0/0 and that’s it).
So we’ll have a look at Show IPV6 route (to see our static default route) and then we need to make sure we can ping R4.
Done!
Now for host route, we’re going to use a 128 bit mask for that one, because just as in v4, a version 6 host route is a route for one destination and one only…
This is going to be a more traditional host route where we were pointing toward a remote destination. So first off let’s go and take that default static route off ( and then verify it)
Let’s go ahead and get the host route to that one IP address over on R4 and get that in place. (this time we’re putting the four in there because that’s the host portion of the address.) We weren’t doing that before with our static routes… I’m going to put 128 bit mask there. So it’s going to match that one and only that one…
you’re either going to put the local router exit interface or the next-hop address…and we’ll just go ahead and put the interface here as well. And that is a host route in version 6.
Then we ping that one host and make sure it works.
There you go.
Note for your exam: When you see a /0 specially ::/0, know that it’s default static route, and when you see a 128 bit mask like the one we just put on that particular route, that’s a host route and it’s going to match only that one particular destination which is good because that’s the one destination we wanted to reach.
IPV6 Nuts And Bolts
What follows isn’t as exciting as configuring routes and checking route tables, but it’s still important info for your exam. We’ll start by answering this musical question:
Why do we need IPV6 in the first place? What’s wrong with IPV4?
In a nutshell, we were running out of IPV4 routable addresses (IPv4 address exhaustion)
While NAT and PAT do a great job in helping ease the pain of this routable address squeeze, they were not thought of as a permanent fix to the problem.
While the IPV6 developers were at it, they came up with other improvements over IPV4:
- The elimination of broadcasts
- Making route summarization and subnetting easier, which helps keep our routing tables – say it with me – complete and concise.
- Eliminating the need for DHCP Servers by allowing hosts to assign themselves an address.
- Quality of Service (Qos) capabilities are much greater with IPV6 header values.
IPv6 Headre Fields
I’m not presenting the IPv4 headre to you to memorize, but you do need to compare it to the IPv6 header. And here we go!
And this is IPV6 header:
Version: Set to “6”, surprising no one.
Traffic Class: The replaces the Type of Service (ToS) field in IPv4. The name refers to this field’s ability to allow us to assign different levels of importance to packets via Quality of Service (QoS), thereby classifying the traffic.
Flow Label: This value also helps with traffic classification and QoS, as it allows a packet to be labeled as part of a particular flow. There is no IPv4 equivalent to this field.
Payload Length: Same thing as Total Length in IPv4.
Hop Limit: Roughly equivalent to IPv4’s Time To Live (TTL) field. Every hop decrements this field by one. When this counter hits zero, the packet is discarded.
Source Address, Destination Address: Same function, just a little longer!
Fields that didn’t make the jump to IPv6: Header Length, Identification. Flags, Fragment Offset, Header Checksum, Options, and Padding.
For the most part these fields were eliminated since they’re unnecessary in IPv6.
For example, Header Length wasn’t necessary since IPv6 headers are fixed at 40 bytes in length, where IPv4 headers are not.
Version 4 headers are not fixed in length. So if every header is going to be 40 bytes What do you need a header length field?
The IPv4 fragmentation field isn’t needed in IPv6 because IPv6 doesn’t fragment packets; that is, IPv6 doesn’t allow packets to be broken up into smaller packets to allow transmission.
What should happen with IPv6 is the hosts performing an end-to-and path Maximum Transmission Unit Discovery (PMTUD).
This process allows the hosts to know how large the packets can be without requiring any kind of fragmentation along the way.
So we got four switches and three routers here but the host do an end to end discovery. with the MTUs are, and then they just don’t send the packet larger than that.
Now if the protocols in use do not allow for that, IPv6 nudes can use an extension header and this one is called the fragment extension header to allow fragmentation of packets.
IPv6 extension headers are far out of the scope of our study so we’re not going to spend any more time on them.
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