CCNA Ch - 7 IP Addressing - FLASH CARDS
Special User IPv4 Addresses
Loopback addresses: 127.0.0.0 /8 or 127.0.0.1 to 127.255.255.254 More commonly identified as only 127.0.0.1, are special addresses used by a host to direct traffic to itself Link-Local addresses: 169.254.0.0 /16 or 169.254.0.1 to 169.254.255.254 - More commonly known as the Automatic Private IP Addressing (APIPA) addresses, they are used by a Windows DHCP client to self-configure in the event that there are no DHCP servers available. Useful in a peer-to-peer connection. TEST-NET addresses: 192.0.2.0/24 or 192.0.2.0 to 192.0.2.255- These addresses are set aside for teaching and learning purposes and can be used in documentation and network Experimental Addresses in the block 240.0.0.0 to 255.255.255.254 that are reserved for future use
Network Address Translation (NAT)
Network Address Translation (NAT) is used to translate between private IPv4 and public IPv4 addresses. This is usually done on the router that connects the internal network to the ISP's network.
Public and Private IPv4 Addresses
Public IPv4 addresses are addresses which are globally routed between ISP (Internet Service Provider) routers. private addresses are not globally routed, they are not allowed on the internet, and must be filtered by internet routers. used by organizations for their internal hosts. private address blocks are: •10.0.0.0 /8 or 10.0.0.0 to 10.255.255.255 •172.16.0.0 /12 or 172.16.0.0 to 172.31.255.255 •192.168.0.0 /16 or 192.168.0.0 to 192.168.255.255
how subnet masks distinguish network from host portions
The process used to identify the network portion and host portion is called ANDing. To identify the network and host portions of an IPv4 address, the subnet mask is compared to the IPv4 address bit for bit, from left to right. The 1s in the subnet mask identify the network portion while the 0s identify the host portion. Note that the subnet mask does not actually contain the network or host portion of an IPv4 address, it just tells the computer where to look for these portions in a given IPv4 address.
Classless Addressing
The system in use today Classless Inter-Domain Routing CIDR, "cider"
Duplicate Address Detection
When a device is assigned a global unicast or link-local unicast address, it is recommended that DAD is performed on the address to ensure that it is unique. To check the uniqueness of an address, the device will send an NS message with its own IPv6 address as the targeted IPv6 address. If another device on the network has this address, it will respond with an NA message. This NA message will notify the sending device that the address is in use. If a corresponding NA message is not returned within a certain period of time, the unicast address is unique and acceptable for use.
EUI-64 Process
When the RA message is either SLAAC or SLAAC with stateless DHCPv6, the client knows the prefix portion of the address from the RA message but must create its own Interface ID. The modified EUI-64 process uses a client's 48-bit Ethernet MAC address, and inserts another 16 bits in the middle of the 48-bit MAC address to create a 64-bit Interface ID. •Step 1: Divide the MAC address between the OUI and device identifier. •Step 2: Insert the hexadecimal value FFFE, which in binary is: 1111 1111 1111 1110. •Step 3: Convert the first 2 hexadecimal values of the OUI to binary and flip the U/L bit (bit 7). In this example, the 0 in bit 7 is changed to a 1.
Network and host portions of IPv4 address
Within the 32-bit stream, The bits within the network portion of the address must be identical for all devices that reside in the same network. The bits within the host portion of the address must be unique to identify a specific host within a network. If two hosts have the same bit-pattern in the specified network portion of the 32-bit stream, those two hosts will reside in the same network. hosts know which portion of the 32-bits identifies the network and which identifies the host via the subnet mask.
IPv6 Link-Local Unicast Addresses
enables a device to communicate with other IPv6-enabled devices on the same link and only on that link (subnet). every IPv6-enabled network interface is required to have a link-local address. If a link-local address is not configured manually on an interface, the device will automatically create its own without communicating with a DHCP server. IPv6-enabled hosts create an IPv6 link-local address even if the device has not been assigned a global unicast IPv6 address, allowing those devices to communicate with other IPv6-enabled devices on the same subnet, including communication with the default gateway (router). IPv6 link-local addresses are in the FE80::/10 range
EUI-64 Interface ID
represented in binary and is made up of three parts •24-bit OUI from the client MAC address, but the 7th bit (the Universally/Locally (U/L) bit) is reversed. This means that if the 7th bit is a 0, it becomes a 1, and vice versa. •The inserted 16-bit value FFFE (in hexadecimal). •24-bit Device Identifier from the client MAC address.
Ethernet MAC addresses
represented in hexadecimal and are made up of two parts: Organizationally Unique Identifier (OUI) The OUI is a 24-bit (6 hexadecimal digits) vendor code assigned by IEEE. And a Device Identifier - a unique 24-bit (6 hexadecimal digits) value within a common OUI.
Logical ANDing
the comparison of two bits to produce a 1 or 0. Only two 1's can produce a 1. The IPv4 address is logically ANDed, bit by bit, with the subnet mask to identify the network address of an IPv4 host.
The Prefix Length
the number of bits set to 1 in the subnet mask
Broadcast Transmission
used to send packets to all hosts in the network using the broadcast address for the network. With a broadcast, the packet contains a destination IPv4 address with all ones (1s) in the host portion all hosts on that local network (broadcast domain) will receive and look at the packet A directed broadcast is sent to all hosts on a specific network (172.16.4.255) A limited broadcast is sent to 255.255.255.255. By default, routers do not forward broadcasts. When a packet is broadcast, it uses resources on the network and causes every receiving host on the network to process the packet. Therefore, broadcast traffic should be limited so that it does not adversely affect the performance of the network or devices
Legacy Classful Addressing
•Class A (0.0.0.0/8 to 127.0.0.0/8) - Designed to support extremely large networks with more than 16 million host addresses •Class B (128.0.0.0 /16 - 191.255.0.0 /16) - Designed to support the needs of moderate to large size networks with up to approximately 65,000 host addresses •Class C (192.0.0.0 /24 - 223.255.255.0 /24) - Designed to support small networks with a maximum of 254 hosts •Class D multicast block consisting of 224.0.0.0 to 239.0.0.0 •Class E experimental address block consisting of 240.0.0.0 - 255.0.0.0. -----Abandoned---*
addresses that must be configured when assigning an IPv4 configuration to host
•IPv4 address - Unique IPv4 address of the host •Subnet mask- Used to identify the network/host portion of the IPv4 address, determined the network address where the device belongs. •Default gateway - Identifies the local gateway (i.e. local router interface IPv4 address) to reach remote networks
Structure of an IPv6 Global Unicast Address
(GUA) are globally unique and routable on the IPv6 Internet (equivalent to public IPv4 addresses). Global Routing Prefix prefix, or network portion of the address assigned by the provider/ISP. Typically, /48. Subnet ID The Subnet ID is used by an organization to identify subnets within its site. The larger the subnet ID, the more subnets available. Interface ID equivalent to the host portion of an IPv4 address, An easy way to read most IPv6 addresses is to count the number of hextets with the fourth hextet indicating the Subnet ID. The remaining four hextets are for the Interface ID.
IPv6 Address Resolution
Address resolution is used when a device on the LAN knows the IPv6 unicast address of a destination but does not know its Ethernet MAC address. To determine the MAC address for the destination, the device will send an NS message to the solicited node address. The message will include the known (targeted) IPv6 address. The device that has the targeted IPv6 address will respond with an NA message containing its Ethernet MAC address
three Responses for RA messages
1: SLAAC: the RA message suggests that the receiving device use the information in the RA message to create its own IPv6 global unicast address and for all other information. The services of a DHCPv6 server are not required. SLAAC is stateless, which means there is no central server allocating global unicast addresses and keeping a list of devices and their addresses. The client device uses the information in the RA message to create its own global unicast address. two parts of the address are created, the Prefix - Received in the RA message, and the Interface ID - Uses the EUI-64 process or by generating a random 64-bit number. 2: Stateful DHCPv6: in which an RA message suggests devices use the router's link-local address, the RA's source IPv6 address for the default gateway address and a stateful DHCPv6 server to obtain a global unicast address, DNS server address, domain name and all other information. 3: SLAAC and Stateless DHCPv6: in which the the RA message suggests devices use SLAAC to create its own IPv6 global unicast address, the router's link-local address, the RA's source IPv6 address for the default gateway address. and a stateless DHCPv6 server to obtain other information such as a DNS server address and a domain name.
IPv4 and IPv6 Coexistence/crossover
Dual stack: allows IPv4 and IPv6 to coexist on the same network segment. Dual stack devices run both IPv4 and IPv6 protocol stacks simultaneously. Tunneling: a method of transporting an IPv6 packet over an IPv4 network. The IPv6 packet is encapsulated inside an IPv4 packet, similar to other types of data. Translation Network Address Translation 64 (NAT64) allows IPv6-enabled devices to communicate with IPv4-enabled devices using a translation technique similar to NAT for IPv4. An IPv6 packet is translated to an IPv4 packet and vice versa
two types of IPv6 multicast addresses
FF00::/8. (IPv6 multicast address prefix) Assigned Multicast : are reserved multicast addresses for predefined groups of devices FF02::1 All-nodes multicast group - a multicast group that all IPv6-enabled devices on the link or network join, like an RA message. FF02::2 All-routers multicast group - a multicast group that all IPv6 enabled routers join. A packet sent to this group is received and processed by all IPv6 routers on the link or network. Solicited-Node IPv6 Multicast Addresses: similar to the all-nodes multicast address, it is mapped to a special Ethernet multicast address allowing the Ethernet NIC to filter the frame by examining the destination MAC address without sending it to the IPv6 process to see if the device is the intended target of the IPv6 packet.
The most common types of IPv6 unicast addresses
Global unicast address similar to a public IPv4 address. Globally unique, Internet routable addresses, can be configured statically or assigned dynamically Link-local address used to communicate with other devices on the same local link (subnet), are confined to a single link, they are not routable beyond the link, in other words, routers will not forward packets with a link-local source or destination address. Packets with a source or destination link-local address cannot be routed beyond the link from which the packet originated. Unique local address used for local addressing within a site or between a limited number of sites should not be routable in the global IPv6 and should not be translated to a global IPv6 address in the range of FC00::/7 to FDFF::/7 can be used for devices that will never need or have access from another network.
ICMP (Internet Control Message Protocol) messages
Host Confirmation: ICMP Echo Message can be used to determine if a host is operational Destination or Service Unreachable : When a host or gateway receives a packet that it cannot deliver, it can use an ICMP Destination Unreachable message to notify the source that the destination or service is unreachable. Time Exceeded: used by a router to indicate that a packet cannot be forwarded because the Time to Live (TTL) field of the packet was decremented to 0
the Neighbor Discovery Protocol (ND or NDP).
ICMPv6 only Messaging between an IPv6 router and an IPv6 device: •Router Solicitation (RS) message •Router Advertisement (RA) message Messaging between IPv6 devices: •Neighbor Solicitation (NS) message •Neighbor Advertisement (NA) message
IPv4 Multicast Transmission range(s)
IPv4 has reserved the 224.0.0.0 to 239.255.255.255 addresses as a multicast range. The IPv4 multicast addresses 224.0.0.0 to 224.0.0.255 are reserved for multicasting on the local network only.
IPv6 Address Representation
IPv6 addresses are 128 bits in length and written as a string of hexadecimal values. Every 4 bits is represented by a single hexadecimal digit; for a total of 32 hexadecimal values, not case-sensitive. x:x:x:x:x:x:x:x, with each "x" consisting of four hexadecimal values Each "x" is a single hextet, 16 bits or four hexadecimal digits.
Router solicitation (RS) and Router Advertisement (RA) messages.
IPv6 routers periodically send out ICMPv6 RA messages, every 200 seconds, to all IPv6-enabled devices on the network. OR, an RA message can be sent in response to a host sending an ICMPv6 Router Solicitation (RS) message. The ICMPv6 RA message includes: •Network prefix and prefix length - Tells the device which network it belongs to. •Default gateway address - This is an IPv6 link-local address, the source IPv6 address of the RA message. •DNS addresses and domain name - Addresses of DNS servers and a domain name.
How IPv6 determines network portion of the address
IPv6 uses the prefix length to represent the prefix/network portion of the address. IPv6 does NOT use the dotted-decimal subnet mask notation. A typical IPv6 prefix length for LANs and most other types of networks is /64. This means the prefix or network portion of the address is 64 bits in length, leaving another 64 bits for the interface ID (host portion) of the address.
two ways in which a device can obtain an IPv6 global unicast address automatically
•Stateless Address Autoconfiguration (SLAAC) allows a device to obtain its prefix, prefix length, default gateway address, and other info from an IPv6 router without the use of a DHCPv6 server. Relying on the local router's ICMPv6 Router Advertisement (RA) messages to obtain the necessary information. •Stateful DHCPv6 (no SLAAC) in which an RA message suggests devices use the router's link-local address, the RA's source IPv6 address, for the default gateway address and a stateful DHCPv6 server to obtain a global unicast address, DNS server address, domain name and all other information. A stateful DHCPv6 server allocates and maintains a list of which device receives which IPv6 address. DHCP for IPv4 is ALSO stateful. When DHCPv6 or SLAAC is used, the local router's link-local address will automatically be specified as the default gateway address.
