For example, the CIDR notation for the IPv4 block 192.168.100.0/22 represents the 1024 IPv4 addresses from 192.168.100.0 to 192.168.103.255.
I'm in an environment where everything is blocked by default, so need to open up the full IPv4-address space on port 443 to give the world access through https.
What is the CIDR notation for all IPv4 addresses?
The so called default route is 0.0.0.0/0 and matches any IPv4 address.
Related
I'm relatively new to the IP Address concept and trying to build a range checker.
USE CASE: The user gives one IP Address(can be IPv4/IPv6) and a range(can be 2 IPv4 addresses /2 IPv6 addresses/ 1 IPv4 and 1 IPv6 address).
I need to test if the given IP exists between the specified range.
I just wanted to know if the below cases are possible
Can an IPv4 address exist between 2 IPv6 addresses?
Can an IPv6 address exist between 2 IPv4 addresses?
Can an IP range be 1 IPV4 address and 1 IPv6 address or do IP ranges implicitly mean the same types(like fromIPv4 - toIPv4, fromIPv6 - toIPv6)?
Note: When talking about IPv6 addresses, I mean all IPv6 addresses and not just those that can be mapped to IPv4.
IPV6 and IPV4 is two different protocols, that don't intersect at all
Just check what pattern IPV4 matches and what pattern IPV6 matches
IPV4 consist of four parts, each part has value from 0-255 and separated with dot.
IPV6 consist of 8 octets, separated with colon sign.
And main reason, why it's unreal to find out, is that IPV4 use netmask for dividing IP address on network part and host part
At the same time IPV6 address is strictly divided on Routing prefix and interface id
I known that I can refer to all IPv4 IP addresses with mask 0.0.0.0/0.
What is the address that matches all IPv6 IP addresses?
It is ::/0, which is short for 0000:0000:0000:0000:0000:0000:0000:0000/0.
I was studying about the IP Class and reserved IP.
Somewhere it said "If an IP address consists of all zeros, the address refers to this host on this network."
What is referred to "this" in phrase "this host on this network"
Originally, the IPv4 address of all 0 (0.0.0.0) meant "This Network." That referred to the fact that it was used as a broadcast address for the network. It is, for all practical purposes, an invalid host address. It is often used for things like routing protocols with a mask length of 0 (0.0.0/0) to represent any address (default route).
The address of all 1 (255.255.255.255) is known as the "Limited Broadcast" address.
The original IP RFCs created the network classes, but they have since been obsoleted by RFCs creating Classless Interdomain Routing (CIDR) and Variable Length Subnet Masking (VLSM). I'm not sure why classful network is still taught today since it isn't really used anymore, but:
Class A addresses all start with a 0 as the first bit in the
address (0.0.0.0 to 127.255.255.255), and they have an 8-bit mask
(255.0.0.0).
Class B addresses all start with 10 as the first two bits in the
address (128.0.0.0 to 191.255.255.255), and they have a 16-bit
mask (255.255.0.0).
Class C addresses all start with 110 as the first three bits in the
address (192.0.0.0 to 223.255.255.255), and they have a 24-bit
mask (255.255.255.0).
Class D addresses (today, used for multicast) all start with 1110
as the first four bits of the address (224.0.0.0 to
239.255.255.255). Multicast doesn't use address masks since each
multicast address represents a multicast group to which host listen
to individually.
Class E addresses (reserved or experimental) all start with 1111 as
the first four bits of the address (240.0.0.0 to
255.255.255.255). Since these are all (except the Limited Broadcast
address) are invalid addresses, they do not use masks.
CIDR and VLSM did away with classful networking, and you should now look at a practical valid address as a series of bits in the range of 1.0.0.0 to 223.255.255.255, having a practical mask length of between 8 (255.0.0.0) and 32 (255.255.255.255).
In reality, IPv4 addresses and masks are just 32-bit unsigned integers on which to perform logical operations. When you are given problems involving IP addresses and masks, it is far easier to convert the dotted-decimal notation into binary to perform the operations, and then convert back to dotted-decimal for the final answer.
What 0.0.0.0 means depends on the context.
To a server process, it means "all IP addresses configured on this host." Let's say you have a host with multiple IP addresses configured, and you want to run a web server on port 443. You can either tell the web server to bind to a specific IP address, or you can tell it to bind to 0.0.0.0, meaning "bind to all IP addresses configured on this host."
In the context of a routing table, it means "the default route," which is sometimes expressed as 0.0.0.0/0. An example routing table:
$ netstat -nr
Kernel IP routing table
Destination Gateway Genmask Flags MSS Window irtt Iface
0.0.0.0 10.131.64.1 0.0.0.0 UG 0 0 0 eth0
10.131.64.0 0.0.0.0 255.255.192.0 U 0 0 0 eth0
172.17.0.0 0.0.0.0 255.255.0.0 U 0 0 0 docker0
This table shows that 0.0.0.0 (the default route) points to the gateway 10.131.64.1. It then points other destinations to the default route at 0.0.0.0.
Here is an iptables ruleset snippet showing the CIDR notation 0.0.0.0/0. You can think of these entries being "FROM any TO any."
Chain INPUT (policy ACCEPT)
target prot opt source destination
ACCEPT all -- 0.0.0.0/0 0.0.0.0/0 state RELATED,ESTABLISHED
ACCEPT icmp -- 0.0.0.0/0 0.0.0.0/0
It is also used in some other cases, e.g. when a host comes up on a network and asks for address assignment via DHCP. If the host has no prior assigned address to try to use, it will be 0.0.0.0 until it has something assigned.
This is all in IPv4. In IPv6, you would see ::/0 instead.
A network is a created by using the subnets, mainly class A,B and C
now IPV4 has 4 octets with 8 bits each
11111111.11111111.11111111.11111111
Now if I take an IP whose bits are as under
11111111.11111111.11111111.11111110 and the subnet is
11111111.11111111.11111111.00000000
It is an ip on the network of a particular subnet, in this example Class C
The 'this network' implies the IP addresses is a member of the network like
11111111.11111111.11111111.11111000
or
11111111.11111111.11111111.11111100
I was studying about IP addresses when I came Across an address of type 127.0.0.1/8. I know that127.0.0.1 is a loop-back address but what did /8 mean in the address.what /8 (in 127.0.0.1/8) specify
the /8 in your ip is the subnet mask.
It allows you to know on which subnetwork you are, find your broadcast and unicast IP.
Take a look at http://en.wikipedia.org/wiki/Subnetwork to have more informations
/8 is a subnet mask written in CIDR notation and which is used by hosts to determine if they are on the same network as some other host and can communicate directly or they need to use a router (default gateway). In your case this is a loopback address, and actually all IP addresses from 127.0.0.0/8 network (from 127.0.0.0 to 127.255.255.255) are reserved loopback addresses as defined in rfc6890: Special-Purpose Address Registries
For example, consider the following network:
IP address: 192.168.0.1
subnet mask: 255.255.255.0
Is the broadcast address required to be 192.168.0.255?
Broadcast Address Defined by RFC 919
Yes, it is required. The (direct) broadcast address is the "all-ones-address" in the local network as defined by RFC 919, thus always the last address in a network range.
Since the local network layer can always map an IP address into data
link layer address, the choice of an IP "broadcast host number" is
somewhat arbitrary. For simplicity, it should be one not likely to
be assigned to a real host. The number whose bits are all ones has
this property; [...]
Examples
For the network from your example, this would be 192.168.0.255, expressed in binary:
11000000 10101000 00000000 11111111
For a network like 10.0.0.32/248 (thus subnet mask 255.255.255.248), it would be 10.0.0.39 (next subnet starts at 10.0.0.40).
00001010 00000000 00000000 00100111
Exemptions
Exemptions exist for /31 and /32 networks. /31 networks (P2P-networks) do not have a broadcast address, they only have two hosts and are sometimes used to connect networks. /32 networks reference a single host together with dedicated routing rules (as there is no gateway).
Yes, though the broadcast address varies dependent on the subnet. From wikipedia:
The broadcast address for an IPv4 host can be obtained by performing a
bitwise OR operation between the bit complement of the subnet mask and
the host's IP address.
Example: For broadcasting a packet to an entire IPv4 subnet using the private IP address space 172.16.0.0/12, which has the subnet mask 255.240.0.0, the broadcast address is 172.16.0.0 | 0.15.255.255 = 172.31.255.255.