Apparently, there are several very distinct topics in routing which have the word “demand” in them. First, there is Cisco On-Demand Routing quasi-protocol, and then there are on-demand circuits which routing protocols must treat differently. Last but not least, the on-demand circuits are used for Routing Backup.
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 »
Sometimes there is a problem: you need to write a really repetitive config with hundreds of nodes. Clear example would be dial peers in Cisco routers. It is immensely hard and dull to do this by hand or copy+paste. Here’s a simple python script to do it for you.
Policy-based routing allows network administrator to stir traffic in directions different from the one chosen by destination-based routing and its routing protocols. This can be useful in several scenarios, namely in dual-homing to different ISPs, as well as other special cases. Using policy-based routing for dual-homing General notes on dual-homing The term Dual-homing in its most general meaning… 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 »
There seems to be an ongoing battle between some people who want an antivirus in every virtual machine and some other people who do not see any benefit it wasting cycles (and memory) on it. Recently, I discovered for myself that there is a middle-ground solution: to run an antivirus centrally for every virtual machine present on the… 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.
Here comes a really tough design question from one of my co-workers: What is a good estimation of the maximum number of hosts per ethernet domain (i.e. VLAN)? Well, when I was first studying networking in college, we generally accepted that about 250 hosts should be the limit and enough for everybody. It was years ago, so let’s… Read More »
Speaking of L2 design, there are several aspects to the VLAN allocation on the switches: standard and extended VLAN ID ranges, reserved IDs, internal usage, protocol limitations and design best practices.