The IP protocol looks up in its routing table to determine whether the destination network is directly accessible by the node or whether it needs the router to route the datagram to the destination network. The IP protocol uses the IP address specified in the destination IP field and the subnet mask to extract the destination IP network address to which the datagram must be routed. The IP protocol is capable of routing an IP datagram within the same IP segment (network address), or else it would need a router to route the datagram to a different IP segment (network address). ![]() The use of broadcast addresses is discouraged. They identify all interfaces on a network. Broadcast addresses are a special case of multicast addresses. If one router needs to pass messages to several other routers, it can do so using multicast addresses. Similarly, it is used in IP distribution of video (IPTV). Multicast addressing is useful for video conferencing, in which the same signal is to be sent to several participants. A router with receiving hosts attached to two or more ports will replicate the packets on each port. This allows a message to be generated once and sent to a number of interfaces. Multicast addresses identify a set of interfaces. A unicast message is intended for one and only one interface. They are assigned to identify a single interface (for most practical purposes this equates to a single host, though there is a difference). Unicast addresses are the most straightforward. There are three types of IP addresses: unicast, multicast, and broadcast. Michael Adams, in Modern Cable Television Technology (Second Edition), 2004 Types of IP Addresses The broadcast address is used by multiple protocols such as ARP, the Routing Information Protocol (RIP), and other protocols that must transmit data before they know the local subnet mask. This address is used to transmit data to all of the hosts on the local subnet. As such, its MAC address is the hexadecimal value of FF:FF:FF:FF:FF:FF. The Ethernet broadcast address is distinguished by having all of its bits set to 1. Additionally, these addresses are often used for transmissions such as bridge spanning tree announcements (used to eliminate loops in switched networks). These addresses are used in conjunction with protocols such as Internet Group Management Protocol (IGMP), in order to reduce the bandwidth consumed by transmitting data to multiple hosts across the Internet. Multicast addresses are distinguished by an odd first byte. There are two classes of MAC addresses: broadcast and multicast. In Hack the Stack, 2006 Performing Broadcast and Multicast Many routers and other devices allow this convention. The double colon at the start is the sign that this is an IPv6 address even though it looks just like an IPv4 address. IPv4 addresses in IPv6 can still be written in dotted decimal as For example, the IPv4 address 10.0.0.1 could be written in IPv6 as (How big are the missing groups of 0 s to the left or right of 9865?)Ī special case in IPv6 is made for using IPv4 addresses as IPv6 addresses. Because only one set of double colons can ever be used inside an IPv6 address, This is better than writing out all 128 bits, even as hexadecimal. The double colon can only be used once in an IPv6 address.Įven with these conventions, the first IPv6 address given earlier cannot be compressed at all. In fact, as long as there is no ambiguity, groups of 0 s anywhere in the IPv6 address can be expressed as. A long string of leading 0 s can simply be replaced by a double colon (::). ![]() For example, any group can leave out leading 0 s, and all-0 groups can be expressed as just a single 0. Some examples of IPv6 addresses follow (you may see the hex “letters” in upper-case or lower-case):ġ080:0000:0000:0000:0008:0800:200 C:417 Aīecause this is still a lot to write or type, there are several ways to abbreviate IPv6 addresses. IPv6 addresses are written in 8 groups of 16 bits each, or 8 groups of 4 hexadecimal numbers, separated by colons. They could be expressed in binary as well, but 128 0 s and 1 s are tedious to write down. All IPv6 addresses are expressed in hexadecimal. There is no such thing as dotted decimal notation for IPv6. The difference between IPv6 anycast and multicast is that packets sent to an anycast IPv6 address are delivered to one of several interfaces, while packets sent to a multicast IPv6 address are delivered to all of many interfaces. In IPv6, multicast addresses serve the same purpose as broadcasts do in IPv4. There are no broadcast addresses at all in IPv6, even directed broadcasts (these were favorites of IPv4 hackers). Walter Goralski, in The Illustrated Network (Second Edition), 2017 IPv6 Address Types and Notation
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