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Multiple IPv6 addresses can be entered, as shown in the following example which uses a long command, not shown for brevity. The first two rows show that 3 of the entered addresses are in a /33 range, while 72 are in a /64. Blocking the /33 would affect 2G /64, that is, over 2 billion /64 allocations, but would block only 3 of the given addresses.
Each / 8 block contains 256 3 = 2 24 = 16,777,216 addresses, which covers the whole range of the last three delimited segments of an IP address. This means that 256 /8 address blocks fit into the entire IPv4 space.
Ranges There are two types of IP ranges CIDR ranges, e.g. 123.123.123.0/24; Non-CIDR ranges; The latter are frequently found in the allocation of IP-address ranges by for instance a provider to a customers or DHCP allocated addresses for certain purposes, as can be found by querying the WHOIS dataase of a RIR.
Used for link-local addresses [5] between two hosts on a single link when no IP address is otherwise specified, such as would have normally been retrieved from a DHCP server 172.16.0.0/12 172.16.0.0–172.31.255.255
In support of link-local multicasts which do not use IGMP, any IPv4 multicast address that falls within the *.0.0.0 / 24 and *.128.0.0 / 24 ranges will be broadcast to all ports on many Ethernet switches, even if IGMP snooping is enabled, so addresses within these ranges should be avoided on Ethernet networks where the functionality of IGMP ...
An IP address is part of a CIDR block and is said to match the CIDR prefix if the initial n bits of the address and the CIDR prefix are the same. An IPv4 address is 32 bits so an n -bit CIDR prefix leaves 32 − n bits unmatched, meaning that 2 32− n IPv4 addresses match a given n -bit CIDR prefix.
The Internet Engineering Task Force (IETF) has reserved the IPv4 address block 169.254.0.0 / 16 (169.254.0.0 – 169.254.255.255) for link-local addressing. [1] The entire range may be used for this purpose, except for the first 256 and last 256 addresses (169.254.0.0 / 24 and 169.254.255.0 / 24), which are reserved for future use and must not be selected by a host using this dynamic ...
Reverse DNS queries are used to map IP addresses to domain names. They are PTR queries for subdomains of in-addr.arpa (for IPv4 addresses) [ 3 ] and ip6.arpa (for IPv6 addresses). [ 4 ] For example, to find the domain name associated with the IP address 203.0.113.22, one would send a PTR query for 22.133.0.203.in-addr.arpa .