Category Archives study

When thinking about tunnelling, which is encapsulating one protocol with another and then transporting that encapsulated packet across a network, you'll soon see yourself seeing terminology such as Transport, Carrier and Passenger protocols. So what is what? The┬ápassenger┬áprotocol is the protocol you want to carry over a network that does not understand it (or you do not want the network…

Today I came across an interesting case when troubleshooting an access list. The device was a Cisco 1921 which had an access list defined to permit certain hosts' incoming traffic from the outside to an FTP server. What was interesting is that the access list only contained permit statements (apart from the implicit deny at the end), but traffic from…

SNMP is an application layer protcol which provides the ability for an agent and a manager to process important information. An agent is on the device you wish to retrieve information from and write it to a database. The database the agent writes to is called the Management Information Base (MIB). If an agent is set to RW, the management…

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