For iBGP number of peers (i.e. the number of BGP routers inside an AS), the only significant limiting factor is that iBGP peers must be fully meshed (N.B.: not directly interconnected! An iBGP peering can span all the hops you can fit into the IP TTL field) – because it is the only way for iBGP to prevent… Read More »
Recently, I tested a Cisco 6500 switch in a fan-less configuration, to see how long it can go. DISCLAIMER: DO NOT TRY TO DO IT. This is a stupid idea and it will void warranty / would be a perfectly valid reason for Cisco to decline RMA (in my opinion at least). Running a switch without fans will… Read More »
An EtherChannel is a way to use multiple physical interfaces as a single logical one. That logical one appears as a single interface to MAC table, STP and management plane. That solves two main concerns: it adds bandwidth and it prevents STP from considering several parallel links a loop, thus preventing it from being blocked.
Sometimes while you do routing, you want to do it in a destination-based way and also differentiate routing for different sub-autonomous systems in your AS. Well, such behavior can be enforced by PBR, but it is not that scalable and it lacks some of the nicer things dynamic routing protocols bring to the table. Enter Virtual Routing and… Read More »
Policy-based routing for IP networks in Cisco routers is a very powerful and precise tool which allows a network administrator to achieve a great many things. In my opinion it should be considered just as fundamental, as general routing mechanisms. How it is different from general destination-based routing and what we can to with it is the subject… Read More »
Internet Protocol Routing, nowadays commonly known as L3 Switching, is part of the process of forwarding an IP packet from Source to Destination. Interestingly, it happens more often then commonly understood: even on a common subnet we often need to make an IP routing decision.