OSPF, BGP, and STP: OH MY!

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Welcome to another installment of the “Tim needs to learn networking better” series. This episode is not really anything specifically NSX related. I want to implement OSPF on my lab network, but before I can do that, I really should understand what it is and what it does. I decided to add a couple other protocols used in the lab. This write-up is simply for my own sanity-checking. If someone else finds it useful, cool!

Note: If you’re a network expert and have any corrections, or anything to add, please do! 🙂


 

Open Shortest Path First (OSPF)

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OSPF is the most widely used of all the Interior Gateway Protocols (IGP – Protocol used inside organizations / networks). OSPF is generally implemented when a network grows too big for RIP to be effective. RIP is not the fastest protocol at scale as it only keeps information about the local router and neighbors. OSPF stores information about the complete topology (Self, Neighbors, and all adjacent segments). This allows devices to calculate what the fastest route is from point to point based on full topology. The protocol works with effective “areas”. This is the equivalent of departments in an office building. The office building would be “area 0” then each of the departments would be the other area #’s. This sets up logical groupings of routers with 0 being the backbone communication area.


Border Gateway Protocol (BGP)

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Border Gateway Protocol is considered “the protocol of the internet”. It is the most widely used Exterior Gateway Protocol (EGP – Protocol used between organizations / networks). BGP allows routers to communicate with autonomous networks (networks outside of your own). The protocol is used to ensure your traffic makes it out of your network, through the vast internet, and into the correct destination network. As IP blocks are not “logically” assigned by geographic region, or anything like that, routers need another way of knowing how to get packets from your network to the destination network. The protocol allows routers to answer other routers that they know where the packets are supposed to go, so to send the info to them so it can be sent on.


Spanning Tree Protocol (STP)

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Spanning Tree Protocol was created before the time of switches, even though it is still widely implemented today on networks with switches. STP is used to ensure loop-free topology in bridged networks. This mitigates the issue of routing loops on the network with logical blocking. The protocol is also implemented to manage purposely-planned redundant loops. This allows for the active-standby use of connection loops, so that when a link goes down, STP can mitigate the dead path by activating the 2nd path.


Thanks for playing along, as always!

-vTimD