The ramblings of a computer geek
Private VLANs provide isolation between ports within a Layer-2 service. Although the configuration is fairly simple, it can become very complex and it also has a number of caveats to how it works and how it can be used. The article explains what Private VLANs are, a brief summary of how they work and then … Read more
Throughout the whole of the series so far we have talked about IPv4. Although there are some differences when using IPv6, fundamentally you’re doing the same thing, you’re using BGP to advertise and route traffic, its just this time you’re talking about IPv6 routes instead. Now, a key thing to remember is that IPv4 and … Read more
So the first question is what is a BGP Looking Glass? It’s an essentially remote router that you access via a CLI terminal (e.g. Telnet), a web interface or sometimes an API which allows you to see: So why would you want to use a Looking Glass? Put simply, to answer questions such as the … Read more
The Routing Information Base (RIB) is one of the key workings of the BGP protocol on a router. The RIB is not just a routing table, it’s a dynamic repository of all the information that a router has learned from BGP Neighbours, along with a host of associated other attributes, such as the route’s AS … Read more
We’ve reviewed many of the key parts of BGP and the way it works, what we haven’t gone into much detail on is security of BGP. BGP as a protocol was developed in a much more trusting era, but over time additional layers of security have been added to BGP and it’s implementations on many … Read more
Equal Cost Multi-Pathing (ECMP) is a mechanism where rather than finding the single best path and installing that into the route table, you instead install two (or more) equal best paths into the routing table; traffic then uses all of these best paths in a load balanced way using the switch’s hashing algorithm. For Extreme Networks XOS this appears … Read more
In previous articles, we have mentioned the use of BFD – Bidirectional Forwarding Detection. RFC 5880. Essentially BGP failure detection is slow by design and for good reason when you are dealing with truly massive networks. BFD exists to make it fast, but also while being safe too. As was discussed in previous articles BGP … Read more
A BGP peer group is: A way to apply the same configuration and policy to multiple BGP neighbours as a single unit. Kinda like Active Directory Group Policy but for BGP Neighbour (peers). If you have specific configuration such as the timers, route policies, BFD and so forth, having to repeat that for multiple peer Router’s … Read more
An Autonomous System (AS) is: A collection of IP networks and routers under a single administrative domain that presents a common routing policy to the Internet. These might be an ISP, a cloud provider, a large enterprise that is running external BGP, a content provider (such as Google or Meta), to identify each of these an Autonomous System Number … Read more
It’s key to understand BGP Timers to understand how and when certain actions will be taken by BGP. BGP timers help the protocol answer these four fundamental questions: Everything else is a refinement of those. Topology and Configuration We’re making some additional changes to the topology, we are adding two new routers, Router K and … Read more