OSPF Cheat Sheet

OSPF (Open Shortest Path First) is an interior gateway protocol. OSPF version 2 is the latest version and is described in RFC2328

Unique ID

Each router in an OSPF network needs a unique ID. The ID determined by the highest IP address on any logical interface. The highest IP from a loopback interface is chosen. If there is no loopback address set then it will use the highest address from any active interface. If no interfaces are up then it cannot obtain an ID.

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IEEE Network Standards Cheat Sheet

802.1Q - Encapsulation protocol used for trunking

ISL - Cisco Encapsulation protocol used for trunking

Wireless:

• 802.11 - 1-2Mbps
• 802.11a = 54Mbps
• 802.11b = 11mbps
• 802.11g = 54mbps
• 802.11n = 600mbps

Spanning Tree Protocol Basics

The nature and purpose of a switch is to forward packets out of all the ports that are in the same VLAN.  When the switch is powered up it goes though a process to block ports that would cause a loop. This is called Spanning Tree Protocol. First all ports are blocked for 20 seconds, they then listen for 15 seconds, learn for another 15 seconds and finally forwarding begins.

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An Easy Way To Work Out Subnets

Understanding subnetting is crucial when working with networks. When studying for my CCNA exam I needed an easy way to be able to work out any subnetting question. I ended up working out the following subnet chart. If you can memorise this, you'll be able to work out any question they can throw at you.

Read more: An Easy Way To Work Out Subnets