The ramblings of a computer geek
Tristan Self 
Can you restore a Microsoft Exchange 2016 or 2019 mailbox database to a Microsoft Exchange SE server? The short answer is yes you can, but you must use the Recovery Database approach. Why would you want to? Well, if like us you are moving at pace to Microsoft Exchange SE to ensure you are on … Read more
You would think that pinging something would be simple, but turns out there is a bit more to it when pinging using IPv6. If you need to ping something from one router to another using IPv4, you can specify the “from” address so the router knows out of which interface (VLAN) it needs to send … 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
Any router that uses BGP must establish a peering (neighbour) with its neighbour routers before it can exchange any routing information. To establish this peering, the BGP router on each side of the connection must go through a number of stages called (BGP States) before it can complete a transfer of routes. A key point … Read more
We’re now going to explore BGP Route Redistribution. BGP Route Distribution is where you can redistribute routes that the router has learnt via some other protocol, e.g. static, OSPF, EIGRP, RIP etc. into BGP, so in effect it becomes a BGP Route. A common example for this might be the redistributing a default static route into … Read more
Within this article we are going to explore BGP Filtering, which is a method used to selectivity identify routes that are advertised (transmitted) or received from neighbour routers (and Autonomous Systems) in order to manipulate traffic flows, reduce memory utilisation or to improve security. It is a very common practice to use route filtering (also … Read more