Monthly Archives: July 2013

Cisco Layer 2 Tunneling

To a student of networking the OSI model can be a little hard to appreciate until its application is actually seen a few times in the real world.  Likewise understanding that you can grab frames or packets and encapsulate them inside other higher layer protocols is also confusing to the newbie.  An Ethernet pseudo-wire is a great example of this.  Essentially, you can capture an entire Data Link layer frame as it enters an interface, encapsulate it, and deliver it out another interface no matter what type of network you have in between.  Cool stuff right?  Let’s dive in and … Continue reading

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Basic Routing Protocol Configuration in VRF Lite

You may recall me posting a basic conceptual article about VRF’s and VRF lite implementation. Well, I am finally back with some more advanced concepts. What good are separate routing instances without the ability to use routing protocols and share routes between routers? Let’s dive right in and see how it’s done! Continue reading

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Administering EtherChannels

EtherChannels, Port-Channels, or Link Aggregation on Cisco switches is a popular and practical feature.  This allows additional capacity to be added to your network without upgrading hardware.  Unfortunately, however, it’s not hard to get confused or to cause an accidental network disruption when working with this feature. Before getting down in the weeds with the configuration, let’s look at the topology we will be working with: Configuration We have two switches.  In this case they are connected with two trunk ports each trunking VLAN 100.  Spanning tree is working as expected and one of the ports on SW2 is in … Continue reading

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