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.
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 »
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 »
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.
In continuation of my last post, here I will write down about EIGRP operation a little mote. Packets On the wire, EIGRP is present with five types of packets: Hello and Acknowledgements (ACKs are just Hellos with the relevant bit set). They are the only EIGRP packets sent unreliably – that is, without acknowledgement. Any other packet must… Read More »
I’ve decided to listen to some advice and use blogging as a learning aid. And to begin with, I’d like to tackle on the subject of EIGRP. It’s no secret that EIGRP is Cisco’s beloved proprietary (it is published as an IETF draft, but apparently public version lacks a feature or two) routing protocol, and thus it is… Read More »