43 lines
1.0 KiB
Markdown
43 lines
1.0 KiB
Markdown
# lec14
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IP Address: 32 bit identifier for a host, router interface
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The interface is that part of a router that connect between a host router and the physical link.
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## Global Addresses
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3 Types of Formats for the addresses
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Type A:
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|1-bit | 7-bits | 24-bits |
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|-------|-----------|-----------|
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|0 | network | host |
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Typb B:
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## Subnets
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If we split the ip address into two (parts) 16-bit portions:
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* subnet - high bits
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* host part - low order bits
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### Subnet mask
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usually we'll have `x.x.x.x/mask` where the mask is also some 1-byte value.
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We can determine the class of a subnet from `mask` value, hereby referred to by subnet mask.
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First we split the 32-bit mask into two portions of 1's and 0's respecctively.
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Example: `255.240.0.0` = `11111111 11110000 00000000 0000000`
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In our example the split happens at offset 12, meaning our x value from before in this case is just 12.
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## Addressing: CIDR
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Classless InterDomain Routing
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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.
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