TCP 3 Way Handshake

For data to be sent across the Internet, traffic is sent over either TCP or UDP. This post will focus on how a TCP session is established, for more information on the differences between UDP and TCP click here.

In order for a TCP session to be established between 2 devices, a process known as the TCP 3 Way Handshake must occur.

How It Works

We know that TCP uses sequence numbers when sending packets, this is part of how the order of packets are verified, and a great way to identify any missing data that might have been lost in transit.

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Configuring TACACS: Step by Step

TACACS is a protocol that is used for the AAA process. If you are unfamiliar with the AAA process, you can click here for a brief explanation on what that is.

This post will go through the configuration of TACACS on a Cisco device to authenticate with an AAA server (Cisco ISE for example) and what the configuration means.

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What is VRF?

What?

  • VRF stands for Virtual Routing and Forwarding.
  • What VLANs do for Switches, VRF essentially do for Routers.
  • It allows us to run multiple instances of routing tables. Essentially we can virtualise multiple instances of a router and have them run on the same physical router device.
  • The same subnet can exist in multiple VRF routing tabled, this allows greater flexibility.
  • A VRF instance must be attached to an interface.
  • The Routing Tables are logically separate from each other. So if we were to check the routing table for each of these instances, we would only see the routes for that instance and no routes for any other instances.

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