Thursday, March 3, 2016

CCNAv2 Notes - Route Summation

Route Summation 
- Must be continuous
- Annotated extra
- Networks often get included

FLSM: Fixed Length Subnet Mask
VLSM: Variable Length Subnet Mask

Super-netting: Route summation mask is smaller than the default for that class of addresses.

IPV4

Basically, what you do is you take the IP, convert it to binary, find where the bits stop being the same, and then find the difference. This will yield both the subnet mask and the host address.

I.E.

172.20.0.0   10101100  .  00010100
172.21.0.0   10101100  .  00010101
172.22.0.0   10101100  .  00010110
172.23.0.0   10101100  .  00010111
===========================
Yields: 172.20.0.0,  /14
Yields: 255.252.0.0

"/14" because 14 bits are all black numbers. When we get to the red ones, you stop adding. 

IPv6 is roughly the same.

2001:DB8:ACAD:1:: 0000000000000001
2001:DB8:ACAD:2:: 0000000000000010
2001:DB8:ACAD:3:: 0000000000000011
2001:DB8:ACAD:4:: 0000000000000100
===============================
The first three octests {2001.... ACAD} are each 16 bits, so 16 * 3 = 48.
We counted 13 matching bits (3 weren't; see red colored text), so 48 + 13 gives us....
61.

"/61" is our subnet mask to whichever address it is used for.


Commands To Apply Routes
Application of this is pretty easy, the command would be, for ipv6 at least, as follows:
>> "ipv6 route 2001:DB8:ACAD:o::/61" "2001:BD8:ABC:1::2"







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