IP Addressing

APIPA (Automatic Private IP Addressing)

A feature if there is no DHCP server on the network. The IP address range for APIPA is 169.254.0.1 through 169.254.255.254. The client also configures itself with a Class B subnet mast of 255.255.0.0 In a corporate network that is running a DHCP server and a host displays an address in the APIPA range it means that either your DHCP client on the host is not working or the DHCP server is down or can't be reached because of a network issue.

Private IP Addresses (RFC 1918)

Address class: Class A Reserved address space: 10.0.0.0 through 10.255.255.255 Address class: Class B Reserved address space: 172.16.0.0 through 172.31.255.255 Address class: Class C Reserved address space: 192.168.0.0 through 192.168.255.255

IPv4 Address Types

Layer 2 Broadcasts: These are sent to all nodes on a LAN. Also known as hardware broadcasts, only go out on LAN, not past LAN boundary (router). Broadcasts (Layer 3): These are send to all nodes on a network. ARP is a good example. Unicast: This is an address for a single interface, and these are used to send packets to a single destination host. Multicast (Class D): These are packets send from a single source and transmitted to many devices on different networks. Referred to as one-to-many.

Network Addressing

Network address - also called network number - uniquely identifies each network. Bits are used to identify network and remaining bits identify hosts. Class A, B, and C are the only ranges that are used to address hosts in our network.

IPv6 Addressing and Expressions

2001:0db8:3c4d:0012:0000:0000:1234:56ab 2001:0db8:3c4d - Global Prefix 0012 - Subnet 0000:0000:1234:56ab - Interface ID Has 8 groups of numbers instead of 4 in IPv4 Uses colons instead of periods. When typing the IPv6 address in the URL you need to put the address in brackets since colon is used in URL to specify port, i.e. [xxxx:address:xxxx] or http://[2001:0db8:3c4d:0012:0000:0000:1234:56ab]/default.html

Special Addresses

Address: 0:0:0:0:0:0:0:0 Meaning: Equals ::. This is the equivalent of IPv4's 0.0.0.0 and is typically the source address of a host before the host receives an IP address when you're using DHCP-driven stateful configuration. Address: 0:0:0:0:0:0:0:1 Meaning: Equals ::1. The equivalent of 127.0.0.1 in IPv4. Address: 0:0:0:0:0:0:192.168.100.1 Meaning: This is how an IPv4 address would be written in a mixed IPv6/IPv4 network environment. Address: 2000::/3 Meaning: The global unicast address range allocated for Internet access. Address: FC00::/7 Meaning: The unique local unicast range. Address: FE80::/10 Meaning: The link-local unicast range Address: 3FFF:FFFF::/32 Meaning: Reserved for examples and documentation. Address: 2001:0DB8::/32 Meaning: Also reserved for exampled and documentation. Address: 2002::/16 Meaning: Used with 6to4 tunneling, which is an IPv4-to-IPv6 transition system. The structure allows IPv6 packets to be transmitted over an IPv4 network without the need to configure explicit tunnels.

Reserved IP addresses

Address: Network address of all 0s Function: Interpreted to mean "this network or segment" Address: Network address of all 1s Function: Interpreted to mean "all networks" Address: Network 127.0.0.1 Function: Reserved for loopback tests. Designated the local host and allows that host to send a test packet to itself without generating network traffic. Address: Host address of all 0s Function: Interpreted to mean "network address" or any host on specified network. Address: Host address of all 1s Function: Interpreted to mean "all hosts" on the specified network; for example, 126.255.255.255 means "all host" on the network 126 (Class A address). Address: Entire IP address set to all 0s Function: Used by Cisco routers to designate the default route. Could also mean "any network." Address: Entire IP address set to all 1s (same as 255.255.255.255) Function: Broadcast to all host on the current network; sometimes called an "all 1s broadcast" or limited broadcast.

Class D and E Addresses

Addresses with the first octeet of 224 to 225 are reserved for Class D and E networks. Class D (224-239) is used for multicast addresses and Class E (240-255) for scientific purposes. Need to know 224.0.0.0 through 239.255.255.255 is the multicast range

Stateless Autoconfiguration

Autoconfiguration is useful because it allows devices to address themselves with a link-local unicast address and with a global unicast address. This process happens through first learning the prefix information from the router and then appending the device's own interface address as the interface ID using part of its MAC. But because IPv6 is 64 bits and MAC is 48 bits below is the process. if MAC is 0060:d673:1987 if would get padded with FFFE and IPv6 for host becomes 0260:d6FF:FE73:1987. so where did the 2 in the beginning come from? It's part of the padding process, called modified EUI-64 format, changes the Universal/Local (U/L) bit to specify if the address is locally unique or globally unique. And the bit that gets changed is the 7th bit in the address. The 7th Bit (U/L) is in the first 8 bits of the OUI of the MAC 10 = Universally Unique 00 = Locally Unique The reason for modifying the U/L bit is that, when using manually assigned addresses on an interface, it means you can simply assign the address 2001:db8:1:9::1/64 instead of the much longer 2001:bd8:1:9:02000::1/64. Also, if you're going to manually assign link-local addresses, you can assign the short address fe80::1 instead of the long fe80::0200:0:0:1 or fe80:0:0:0:0200::1. Examples: MAC address - 0090:2716:fd0f IPv6 EUI-64 address - 2001:0db8:0:1:0290:27ff:fe16:fd0f MAC address - aa12:bcbc:1234 IPv6 EUI-64 address - MAC address - 0c0c:dede:1234 IPv6 EUI-64 address - MAC address - 0b34:ba13:1234 IPv6 EUI-64 address -

IP Terminology

Bit: A bit is one binary digit, either 1 or 0 Byte: A byte is 7 or 8 bits, depending on whether parity is used. Octet: An octed, made up of 8 bits, is just an ordinary 8-bit binary number, byte and octet are interchangeable. Network Address: This is the designation used in routing to send packets to a remote network - for example, 10.0.0.0, 172.16.0.0, and 192.168.10.0. IP Address: A logical address used to define a single host; however, IP addresses can be used to reference many or all hosts as well. If you see something written as just IP, it is referring to IPv4. IPv6 will always be written as IPv6 Broadcast Address: The broadcast address is used by applications and hosts to send information to all hosts on a network. Examples include 255.255.255.255, which designates all networks and all hosts; 172.16.255.255, which specifies all subnets and hosts on network 172.16.0.0; and 10.255.255.255, which broadcasts to all subnets and hosts on network 10.0.0.0.

Migrating to IPv6

Dual Stacking - Allows both IPv4 and IPv6 running at the same time on devices. 6to4 Tunneling - IPv6 traffic is encapsulated over IPv4 header over the IPv4 WAN. Teredo - Allows all your tunnel traffic to be placed in UDP packets. It's used to slip by NAT process for IPv6 packets. Miredo - Tunneling technique used on native IPv6 Linux and BDS Unix machines to communicate on the IPv4 Internet directly without a dual-stack router or 6to4 tunnerl (rarely used).

Class B Addresses

The 1st 2 bytes are assigned to the network address and the remaining 2 bytes are assigned to the network address and the remaining 2 bytes are used for host addresses. network.network.host.host. With a network address being 2 bytes (8 bits each), we're left 2^16 unique combinations. But the Internet designers decided that all Class B network addresses should start with the binary digit 1, the 0. This leaves 14 bit position available to manipulate, so in reality, we get 16,384 (thats 2^14) unique Class B addresses. In Class B network, the RFCs state that the 1st bit of the byte must always be turned on but the 2nd bit must always be turned off. If we turn the other 6 bits all off and then all on, we find the range for a Class B network: 10000000 = 128 10111111 = 191 A Class B network is defined when the first byte is configured from 128 to 191. A Class B address uses 2 bytes for host addresses. This is the 2^16 minus 2 reserved patterns (all 0s or all 1s), for a total of 65,534 possible host addresses for each Class B network.

Class C Addresses

The 1st 3 bytes of a Class C network address are dedicated to the network portion of the address, with only 1 byte remaining for the host address. The format is: netowrk.network.network.host In a Class C network address, the 1st 3 bit positions are always in binary 110. The calculation is as follows: 3 bytes, or 24 bits, minus 3 reserved positions leaves 21 positions. Hence, there are 2^21, or 2,097,152, possible Class C networks. For Class C networks, the RFCs define the 1st 2 bits of the 1st octet as always turned on, but the 3rd bit can never be on. We find the range for a Class C network: 11000000 = 192 11011111 = 223 IP address with a range from 192 up to 223 is a Class C IP address. Each unique Class C network has 1 byte to use for host addresses, This gets you 2^8, or 256, minus the 2 reserved patterns of all 0s and all 1s for a total of 254 available host addresses for each Class C network.

Class A Address

The first byte is assigned to the network address, and the three reaming bytes are used for the host addresses. The class A format is as follows: network.host.host.host Class A network addresses are 1 byte long, with the 1st bit of that byte reserved and the 7 remaining bits available for manipulation, or addressing. The theoretical maximum number of Class A networks that can be create is 128 due to the 7 bit positions can be either a 0 or 1 and 2^7 gives you 128. The designer of the IP address scheme said that the first bit in a Class A network address mush always be off, or 0. This means a Class A address must be between 0 and 127 in the 1st byte, inclusive. So, a Class A network is defined in the first octet between 0 and 127, and it can't be less or more. The network address of all 0's is reserved for default route. Additionally, the address 127 is reserved for diagnostics and can't be used which means that you can really only use then numbers 1-126.

DHCPv6

Works the same as IPv4 just accepts IPv6 addressing scheme.

Address Types in IPv6

Unicast - Packets addressed to a unicast address are delivered to a single interface, same as in IPv4. For load balancing, multiple interfaces can use the same address. Global Unicast Address - These are you typical publicly routable addresses, and they're used the same way globally unique addresses are in IPv4. Link-Local Address - These are like the APIPA addresses in IPv4 in that they're not meant to be routed and are unique for each link (LAN). Think of them as a handy tool that gives you the ability to throw a temporary LAN together for meetings or for creating a small LAN that's not going to be routed but still needs to share and access files and services locally. However, link-local is used on every LAN that connects to a router interface(s) as well. Unique Local Address - These addresses are also intended for nonrouting purposes, but they are nearly globally unique, so it's unlikely you'll even have one of them over-lap with any other address. Unique local addresses were designed to replace site-local addresses, so they basically do almost exactly what IPv4 private addresses do-allow communication throughout a site while being routable to multiple local networks. The difference between link-local and unique local is that unique local can be routed within your organization or company. Multicast - Again, as in IPv4 packets addresses to a multicast address are delivered to all interfaces identified by the multicast address. Sometimes people call them one-to-many addresses. It's really easy to spot multicast addresses in IPv6 because they always start with FF. Anycast - Like multicast addresses, an anycast address identifies multiple interfaces, but there's a big difference: The anycast packet is delivered to only one address - actually, to the first IPv6 address it finds defined in terms of routing distance. And again, this address is special because you can apply a single to more than 1 interface. You could call them one-to-one-of-many addresses. This is also referred to as one-to-nearest addressing.

The Hierarchical IP Addressing Scheme

You can depict an IP address using one of three methods: * Dotted-decimal, as 172.16.30.56 * Binary, as in 10101100.00010000.00011110.00111000 * Hexadecimal, as in AC.10.1E.38 A 32-bit IP address is known as a structured, or hierarchical, address as opposed to a flat, or non-hierarchical, address. The disadvantage of the flat-addressing scheme, and the reasons it's not used for IP addressing, relates to routing. If every address were unique, all routers on the Internet would need to store the address of each and every machine on the Internet making routing impossible. The solution to this problem is to use a two- or three-level hierarchical addressing scheme that is structured by network and host or by network, subnet, host. This two or three level scheme is comparable to a telephone number. The first section, the area code, designates a very large area, The second section, the prefix, narrows the scope to a local calling area. The final segment, the customer number, zooms in on the specific connection. IP addresses use the same type of layered structure. Rather than all 32 bits being treated as a unique identifier, as in flat addressing, a part of the address is designated as the network address and the other part is designated as either the subnet and host or just the host address.

Shortened Expression for IPv6

You can drop leading 0s i.e. 2001:db8:3c4d:12:0:0:1234:56ab You can replace blocks of 0s with double colon only once if there are multiple contigous blocks not next to each other you can only do one of them i.e. 2001:db8:3c4d:12::1234:56ab given below 2001:0000:0000:0013:0000:0000:1234:56ab you CANT do this 2001::12::1234:56ab best you CAN do is this 2001::12:0:0:1234:56ab

Internet Protocol Version 6 (IPv6)

improves a lot on IPv4 by making certain standards mandatory. IPSec (end-to-end security), mobility (move from network to network no issues), are some improvements. IPv6 header has half the fields of IPv4. New addresses available are (3.4 x 10^38). No broadcast in IPv6, It uses multicast, unicast and anycast which allows the same address to be placed on more than one device so that when traffic is sent to one device addressed in this way, it is routed to the nearest host that shares the same address. 128 bits.