#Ipv6 subnet mask table 64 Bit#
Although it is technically possible to design networks with a smaller host portion, it is impractical because stateless autoconfiguration is one of the biggest advantages of IPv6, and it requires a 64 bit prefix.ĭue to the MASSIVE increase in address space, “IPv6” and “subnetting” are two terms that are logically disjoint.
#Ipv6 subnet mask table 64 bits#
So, with that 16-bit subnet portion, IPv6 global unicast addresses always have 64 bits in their host portion.
#Ipv6 subnet mask table how to#
If not, its sent to a router that knows how to get to that IPv6 subnet. This concept is exactly the same in IPv6 - if the first four quartets are the same in a /64, its on the same subnet, and its sent straight to the host. If not, it was sent to the default gateway for routing. If the IP address was on the same subnet, it was sent to the MAC address in the ARP table associated with that IP. This portion of the address is analyzed in the same way the entire subnet mask in IPv4 was analyzed by PCs to determine if a destination is on the same subnet. In this example, its actually the fourth quartet in the address, which is visible in the address as “1”, or in uncompressed notation, “0001”. So what happened to those 16 bits? That, my friends, is our subnet portion. Remember that the actual address had a /64 notation at the end. That means that the whole company, using this block, will use addresses that all start with 2001:42b:7a5, since those are the characters described by the first 48 bits of the address. These characters will be seen on EVERY address in that block. This is not an address, but rather a large block of addresses (notice that there is no number at the end, only the “::") The /48 describes, again, that the first 48 bits of the address will not change. This block might look like this: 2001:42b:7a5::/48 Lets say that address was part of a block allocated to our company by our ISP. Much like IPv4, this notation describes which part is the network portion of the address (doesn’t change from host to host), and which is the host portion. You’ll notice in the above example that I threw on the “/64” to that IPv6 address. Its one of those concepts that’s been ingrained into our minds as a fundamental component to designing and running a network. For those that have worked in the networking industry for a while, or have had a networking education that primarily focused on IPv4, as mine did, you’re used to subnetting. The internet does NOT have a lot of information regarding IPv6 subnetting. While IPv4 addresses were traditionally read in decimal form, IPv6 addresses are usually shown in hexadecimal form. A pretty standard mask could be: 255.255.255.0 You’ve probably also seen these addresses accompanied by their “subnet masks”.
These are commonly seen in the following format: 192.168.0.1 With IPv4, subnet masks are used to determine how big the subnets are.Ī standard IPv4 address requires 32 bits to describe it. This is useful if you know how many IP addresses you’ll to suit the needs of a predetermined number of PCs, so you can plan the size of your subnets to match that requirement.
Subnetting, in short, can be thought of as an adjustable “slide rule” that tells the network infrastructure the logical size of a sub-network, or subnet.