IPv6 Basics for Beginners

let's learn some ipv6 basics first of all binary conversion here's an ipv4 address 32 bits converted into binary here and then the subnet mask converted into binary here / 24 and then 24 ones and eight zeros and then the octet here the 192 octet eight bits eight bits here and so we have four octet s-- now in contrast an ipv6 address is a hundred and twenty eight bits and the characters are hexadecimal characters so each character is four bits and we call these hex tats so you have four characters in hex Tet another hex Tet so there's eight hex tetes 128 bits and here's what it looks like if you convert it to binary and I've put a dash here to identify each each character so this is the two right here and then the 0 here and the 0 and then the 1 so just this right here is the first hex 10 alright let's look at the next slide ipv6 128 bit address colon separated hexadecimal notation a text heads on every interface you need a link local address on each interface now the link local address is locally significant only it's not routable to another network it's not routable on the internets it's only you can only use it or communicate to it on the local link which means the local network you can have multiple routable addresses on and in on each interface so each interface can have multiple routable ipv6 addresses and there's different types there's a global unicast address now this is a unicast address that you could put on your interface on your router or on your PC and it's routable on the Internet it's basically the equivalent of a public ipv4 address global unicast address would be like a public routable ipv6 address and now a unique local address is also unicast it's for a host just like a global unicast a unique local is for host however it's a private address so it's similar to an ipv4 private address now we don't actually really need these in ipv6 because ipv6 address space is so huge that every device on in the world if they had an ipv6 address we could have all public addresses easily ten times over a hundred times over all the devices in the world could have a unique public ipv6 address however since a lot of network admins are used to having private addresses that are only routable on a private network they came up with unique local addresses that are private ok there's any caste addresses and anycast address is the same as a unicast address but you can assign the anycast address to multiple devices in other words you could have three routers with the same address and then it would be in any caste address you could configure it as in any caste address and then if you want to reach the router you would reach the nearest device basically the first device to respond and that's any caste so same address on multiple devices and then the nearest one responds in ipv6 we don't have any broadcast addresses no broadcast addresses only multicast addresses multicast addresses are similar to broadcasts in a way because they get sent out to multiple devices on a network so we use multicast addresses and set a broadcast then each ipv6 address will have a slash network prefix it's in a slash decimal notation so when you see slash 64 the 64 is actually in decimal it means that there's 64 ones in the network prefix there are no subnet masks in ipv6 we don't use subnet masks in the same way like we do in ipv4 there's no ending of the IP address with a subnet mask to find the network in ipv6 the slash 64 here lets you know that the network prefix is 6 for a bit long 64 bits long and that defines the network so here is a global unicast address example I just I just made this up by the way so you have here slash 64 that means this is the 2001 to eb8 ADC 154 IDI Network and then this is the the interface ID or they basically like the host address then a link local address this is locally significant only every interface would need to be routable on a network routable address like a global unicast address or a unique local address and then a link local address which is only for the local link or local land and those start with fe80 and you can see it here and the slash ten defines it that link local is defined by the first ten bits which is the F the e and then a portion of this eight alright let's look at the next slide so the network prefix the network prefix separates the network portion from the interface ID the network prefix refers to the number of bits in the network portion I've already stated that so here we have a global unicast address you see the slash 64 that means the first 64 bits or the first four hex tats is the network and then the last four hex tats is the interface ID similar to like the host address it identifies the interface and then here we have a slash 96 in this case the network would be defined by 96 bits and then the remaining bits would identify the interface ID and then let's say you had a / 128 network prefix well that means that the whole thing is a network of 1 essentially kind of like a / 32 identifies a single host or a network of 1 on to the next slide so let's break down an ipv6 global unicast address the network portion of the global unicast address is hierarchically structured so if we look at those first 64 bits the first 3 bits is the IA n a global prefix so of the globally routable addresses currently that we're using in ipv6 is just a small portion of what's the total address available space so the first three bits identifies the ia na addresses that have been assigned to be used on the internet then the next bits the next 20 bits up to bit 23 is the regional registry so these these numbers here would identify your regional registry whether it's North America South America Africa Asia etc then the next bits here the next nine bits here would be your service provider prefix so this would be assigned to your internet service provider and then your internet service provider will assign you your site prefix which is between bit 32 and bit 48 this is your site prefix so this would be your company or your organized organized a ssin if you purchased an ipv6 address from your service provider this would be your static IP address our ipv6 address of your organization then the last hex Tet in the network prefix is the subnet pecs Tet and then you can assign this so effectively you would be okay this is my company this uniquely identifies my company the two-two three-three here and then I can put my own subnet using these four hexadecimal characters so I can assign my own subnet then you have the last 64 bits which is the interface ID identifying the host or the interface on the network let's talk about ipv6 address compression let's face it the ipv6 address is super long it's super long right 32 characters is a lot of characters so address compression is allowed in other words we can write this address this is the complete address we can compress it down to this address now how do we compress and decompress an ipv6 address it's not hard what you do is here's a couple of rules leading zeros can be omitted so here we go we have zero eb8 so this leading zero can be omitted so instead you could have bb8 all right and then you have 0 0 c1 here so these leading zeros these two leading zeros can be omitted so you just have c1 and then notice over here in the subnet prefix portion subnet portion we have 0 0 0 1 so that could be reduced down to just 1 we can omit these 3 leading zeros then the next rule is that a single instance of continuous zeros can be replaced with a double colon so notice we have these continuous zeros here we have 8 and then 9 continuous zeros here so you could take this whole block of zeros here and change it to just a double colon and this identifies a range of zeros a range of continuous zeros now if you follow these rules you could successfully decompress this address back to the full address length here but anyway this is a compressed ipv6 address when decompressing remember there are supposed to be eight hex tetes of four hexadecimal characters each that will help you to decompress this address is that you know there needs to be there needs to be eight hex tats so we know that well if this is this is easy this is 0e b8 and we know this is 0 0 c1 and then we know this is 0 0 0 1 well that means we have 1 2 3 4 5 hex tats that means we need three more hex tats so we've got two hex tents of zeros and then we need to add a 0 before that 3 and we've got our three hex tats remaining so that's basically one of the things you need to remember when decompressing is that they're supposed to be 8 hex tetes total in the address that'll help you okay let's talk about another interesting feature of ipv6 and that's slack stateless address auto-configuration with ipv6 essentially a host that uses ipv6 on a network doesn't need a DHCP server to get an address on the network and I'll return to that later because it turns out actually they do kind of but for the most part they don't so in other words if you have a host a PC here on the network it can basically stateless lis auto-configure it's ipv6 address so how's that done well the PC sends a router solicitation which is actually an ICMP version 6 message it basically says hey where's the router on the network now the router is also advertising and the router saying hey I'm over here so the router responds to the PC when the router when the PC gets the response from the router the router can auto configure the address using eui-64 extended unique identifier and basically what that is is it's basically converting your 48-bit MAC address into a 64-bit interface ID or the PC could randomly configure the interface ID portion so this is the auto configure part where the PC auto configures the 64-bit enter face ID it can be done using eui-64 basically using the MAC address or it could be random and randomly configure it then once the pc has given itself auto configured its ipv6 address and it's learned about the network portion and the gateway and the network prefix from the router it sends out a neighbor solicitation message also known as duplicate address detection to basically ping itself and make sure that there's no other device on the network with that address since the pc auto configured the address there is a slight chance that there might be another device out there on the network that has the same address so it sends out a ping just to make sure that no response comes back let's take a closer look at this ipv6 slack so RFC 4860 one neighbor discovery slack ICMP version six I said it uses ICMP to do this let's take a look at it step one you've got the router solicitation message now in the source address field it's going to be an unspecified address because your PC doesn't have an address yet so it'll be colon colon slash 128 I don't have an address the destination address will be the all routers multicast address which is FF 0 2 which identifies it as a multicast colon colon 2 so this will go out this multicast will go out and routers will pick it up this is a type 133 packet okay then here comes the response step 2 the router advertisement now the router advertisement is sent periodically on the network but it can also be sent in response to that router solicitation message so in the source address feel the router will have its link local address this is how you'll learn where the router is where the Gateway is this is where you learn the Gateway and then you'll put that into your gateway at your gateway address and the destination address for the router advertisement is the all nodes multicast address FF 0 2 colon colon 1 so this will go out to all device is on the network essentially advertising that we have an ipv6 router it's a type 134 in the type field okay so then type 133 in the message and type 134 in the message okay now what is in this router response in this router response is the ipv6 prefix which could be either one or more prefixes if there's multiple networks however in this case what will the PC learn from the router the PC learns that it's the two thousand one two three four a b c d e f 22 network notice it learns that the network the network portion of the address it also learns the / 64 prefix the network prefix however it doesn't learn the ipv6 interface ID because it's going to auto configure that it also learns the router lifetime information how long this information is valid there's going to be some flag information in here and the flag information is either going to be nothing or it's going to be M for managed or Oh for other now this is the part that that helps you get your DNS server so the one thing that the router doesn't tell you is where the DNS server is so you're either going to have to statically configure your DNS server on your host or if there's a DHCP version 6 server on the network that's serving just the DNS server information then the router will set the flag letting the PC know to go find the DNS server information from the DHCP version 6 server on the network that's the oh there's other information namely DNS server and it's out there on a DHCP version 6 server go find it if there's an EM flag it means ignore the network ignore the network prefix ignore this router except for the gateway address and go find your go get a leased ipv6 address from a DHCP version 6 server that's going to lease you an address the other thing that once again I mentioned is you learn the gate the source address of the router the fe80 link local address you learn that from the reply from the router advertisement so we have that listed here too so that is basically how you get most of the information off the network - the DNS server which you're going to need to get from a DHCP version 6 server or statically configure now let's talk about eui-64 ipv6 slack eui-64 extended unique identifier so this is when you convert your 48-bit MAC address into a 64-bit host interface ID so notice 48-bit MAC address into 64-bit host ID so here it is there's my MAC address 48 bits hexadecimal and here's my interface ID the result is a 64-bit hexadecimal interface ID so what happens well it's pretty simple the MAC address gets split into two pieces and FF : Fe is inserted in the middle so notice we've got f FF e in the middle now then on this this address the seventh bit from the left so if you have 0 8 here in your MAC address so 0 8 if we convert the zero 8 to binary so we have 4 bits that's the 0 here's another 4 bits that's the 8 the 7th bit so 1 2 3 4 5 6 that's this yellow one right here gets flipped so it'll flip from a 0 to 1 and what that does is it changes 0 8 to 0 a because we flipped that bit right here which is in the twos place and so now we have 2 more so 8 plus 2 more is na so you have 0 a instead of 0 8 so that's it FF Fe is inserted in the middle of your MAC address and the 7th bit is flipped and that's it alright next slide the other piece of ICMP version 6 for ipv6 that is used on the network is neighbor discovery so let's take a look at that RFC 48 61 neighbor discovery so the neighbors solicitation so a neighbor solicitation message is similar to ARP in ipv6 it checks also can be used to check for hosts availability and it's used to check for duplicate address detection after you auto configure your address you need to ping your address to make sure there's no other address on the network so let's look at it in the source address you're gonna have your link local address or an unspecified address if duplicate address detection so if it's duplicate address detection you'll have unspecified if its neighbor solicitation similar to our peur trying to find a host on the network you're basically trying to resolve the MAC address of the host on the network then it'll have your link local address in here then the destination address is the all solicited nodes multicast now this is interesting because this is actually an improvement on Arps function so the destination address will be FF 0 2 which is multicast and then colon colon 1 call an FF and then the last 28 bits of the destination hosts ipv6 link local address so in other words this multicast is multicast essentially to the device that it needs to go to so in other words this is you you already have to know the devices link local address for this neighbor solicitation what you're trying to resolve is the MAC address so the switch if the switch has been configured to be able to do this it can actually forward this message directly to the device on the network so in other words instead of like an ARP which gets broadcasted and broadcast it to the whole land this all solicited nodes multicast essentially is multicast one device only so it's a multicast that will get picked up only by one device and essentially it can also be sent to one device if a switch has been configured properly or has the ability to do that so then what about that's the neighbor solicitation it's an all solicited nodes multicast and then the neighbor advertisement the response to the neighbor solicitation and it's used to announce a link layer address change so if you were to change your link layer address you would send out a neighbor advertisements a hat changed my my link layer address so your link local address is in the source the destination is the link layer address or the all nodes multicast if you're using to announce a link layer change then there's some flags the our flag router flag neighbor unreachable s solicited flag responds to a neighbor solicitation or the OU flag and override flag where you're updating your address so in a flag here if it's an update of an address it will be oh if it's responds to neighbor solicitation and it's a neighbor advertisement that'll be an S and then if it's a neighbor unreachable router flag it won't have an R and this is the type in the message field all right this is a useful slide for you for learning ipv6 address types a global unicast address that's routable on the internet will generally have the prefix 2000 they'll be a 2 here or typically 2001 or a number like that so typically it's 2000 if it's a global unicast if it's linked local it starts with fe80 if it's a multicast it starts with F F if it's a unique local routable on a land private address it's an ipv6 private address it'll start with F C or typically F D modified eui-64 converting the 48 MAC address to 64-bit host ID the 7th bit is flipped and FFA Fe is inserted in the middle Auto configuration slack uses reroute er solicitation router advertisements neighbor solicitation neighbor advertisements and it uses ICMP version 6 this is how how it's done in any cast address is a shared address used to send to the nearest available device interface it's sing tactically identical to an unicast address so the address for in any cast adders could be the same as your unicast address or and this is curious if you have the address with all zeros in the interface ID portion so you have the network prefix and then all zeros it's me that reminds me of a network address in ipv4 this actually can be used as an anycast address with all zeros in the ID portion all right moving on specific ipv6 addresses that you'll want to know so colon colon slash zero is the all networks address used for the default route so colon colon slash zero is similar to a quad zero route in ipv4 in other words 0.0.0.0 space subnet mask 0.0.0.0 this is similar to that it's all zeros in the address and all zeros in the network prefix it's used for default route colon colon 1 / 128 colon colon 1 is your loopback address you can ping yourself open up your command prompt and ping colon colon 1 and you'll get a reply you're pinging yourself in ipv6 you're essentially pinging your link local address an unspecified address means I don't have an address yet is : : / 128 your link local address starts with fe80 colon colon slash 10 on the prefix FF 0 to colon colon 1 is all nodes FF 0 to colon colon 2 is all routers multicast and then FF 0 2 : : 1 : FF and then you have 28 bits 6 hex characters of the address that's the all solicited nodes multicast it's used in Auto configuration and neighbor discovery it's similar to ARP the processes you need to discover this is used when you need to discover the MAC address of the neighbor alright configuring the ipv6 address on the router it's it's really simple first of all you'll go into global config mode you'll put in ipv6 unicast routing this will turn on ipv6 routing on the router you need this ipv6 unicast routing to enable the router to start doing router advertisements you know to respond to router solicitations and issue router advertisements things like that you need that ipv6 Tina cash - routing then to configure an address here we go ipv6 address on the interface and then the address slash 64 so that's like statically configuring an ipv6 address on the network then this one ipv6 address the network portion then colon colon all 0 slash 64 and then you put in space EUI 64 and then the router will create and a unique identifier based on the MAC address and put that in here automatically ipv6 address fe80 : : 1 this is basically configuring space link - local the link local address on your router remember you need two addresses one that's let's say routable like this one and then you would need the link local one here so you could use either this or this but you're going to need this a link local address and in this case it's statically configured so let's say I'm router r1 I said fe80 : : 1 just host 1 over here let another way to do it is you could say ipv6 enable enable ipv6 addressing on the interface and then ipv6 address Auto config will Auto configure your link local address basically using eui-64 for the interface ID portion so you'll end up with fe80 and then you'll have colon : and then for hex tetes worth of a 64 bit interface ID configured from your MAC address to get rid of an ipv6 address this is a tricky one with ipv4 you could just say no IP address right we used to be able to say just no IP address to get rid of an address on an interface but with ipv6 since you can have multiple addresses on the interface you need to type the whole thing to get rid of the address no and then the complete address to get rid of it and then no and then this will get rid of the link local but it's a little bit longer because you have to type in the whole address

Channel: danscourses

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Keywords: IPv6, addressing, basics, beginner, types, ICMPv6, SLAAC, EUI-64, CCNA, danscourses, autoconfigure, unicast, anycast, multicast, neighbor, router, rs, ra, ns, na, all solicited nodes

Id: z7Al3P8ShM8

Length: 27min 58sec (1678 seconds)

Published: Fri Nov 01 2019