My experiences with the Cisco CCNA Exam
From Poggs' Wiki
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I took, and passed, my Cisco CCNA - with nine years experience and some on-and-off revision, I found it fairly straightforward and not at all taxing. Here are my experiences and tips.
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IP subnetting
Learn it - you won't get away without it. It helped me enormously to write a little table which I learnt off by heart:
| /n | Mask | Hosts |
| 32 | 255 | 1 |
| 31 | 254 | 2 |
| 30 | 252 | 4 |
| 29 | 248 | 8 |
| 28 | 240 | 16 |
| 27 | 224 | 32 |
| 26 | 192 | 64 |
| 25 | 128 | 128 |
| 24 | 0 | 255 |
Here's how to do it:
- Write 32 down to 24 in the first column.
- Write 255 at the top of the second column, then 1 in the third column.
- Subtract the value in the third column from that in the second, and write the figure in the second column, then double the figure in the third column.
- Continue.
If you can, memorise:
- A /30 is usually used on point-to-point interfaces (although you could use a /31)
- A /29 is about the right size for a home ADSL connection - five or six usable hosts
- A /28 is about the right size for a DMZ on a commercial firewall for a smaller company
- A /27 is an eighth of a Class C
- A /26 is a quarter of a Class C
- A /25 is half a Class C
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Network Diagrams
Some of the network diagrams will make no sense in the real world. For example, two sites with /24s connected over a leased line and no other networks will probably use static routes, rather than RIP.
Think laterally - and work out what you can learn from CDP that you couldn't from other sources - e.g. the IP address of remote routers.
