1.1 KiB
lec14
IP Address: 32 bit identifier for a host, router interface The interface is that part of a router that connect between a host router and the physical link.
Global Addresses
3 Types of Formats for the addresses
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Type A:
- Lower 3-bytes are clobbered
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Type B:
- Lower 2-bytes are clobbered
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Type C:
- Lower 1-byte is clobbered
Subnets
If we split the ip address into two (parts) 16-bit portions:
- subnet - high bits
- host part - low order bits
Subnet mask
usually we'll have x.x.x.x/mask where the mask is also some 1-byte value.
We can determine the class of a subnet from mask value, hereby referred to by subnet mask.
First we split the 32-bit mask into two portions of 1's and 0's respecctively.
Example: 255.240.0.0 = 11111111 11110000 00000000 0000000
In our example the split happens at offset 12, meaning our x value from before in this case is just 12.
Addressing: CIDR
Classless InterDomain Routing
This says that any address say: a.b.c.d./x will tell us that x is the bit offset in the subnet portion of an address.