Link state protocols like OSPF and IS-IS use the Shortest Path First (SPF) algorithm developed by Edsger Dijkstra. Edsger was a Dutch computer scientist, programmer, software engineer, mathematician, and science essayist. He wanted to solve the problem of finding the
IS-IS Behavior on Multi-Access Networks
In many ways, IS-IS is a simpler, and perhaps more elegant, routing protocol than OSPF. However, it often gets misunderstood. Perhaps due to its roots in OSI or perhaps because it’s not as widely deployed as OSPF. Some of the
Route Replication the Easy Way
Easy Virtual Network (EVN) was a technology Cisco came up with back in the days to make it easier to implement VRFs without the pain of running VRF lite or the complexity of running a full MPLS + BGP network.
General – Advice on Numbering Policies in Networking
There are several situations where we need to write some form of policy such as QoS, routing policies used in for example redistribution, filtering and policy-based routing, dot1x and so on. Lately I had to update a policy used by
General – Challenges in Load Balancing Traffic
For the last year I have been working a lot with IWAN which is Cisco’s SD-WAN implementation (before Viptela acquisition). One of the important aspects of SD-WAN is to be able to load balance the traffic. Load balancing traffic is
EIGRP named configuration
You might think that EIGRP being around for so long is not getting any attention from Cisco, not true. EIGRP is still being developed and in later releases you can run what is called named configuration. Doing this you can
Tiebreakers with routes from different OSPF processes
This post is inspired by a discussion at Twitter with Ivan Pepelnjak and Nicolas Michel. Nicolas asked what happens when there is the same route from two different OSPF processes. Which one will be selected? Ivan explained how to use
Route redistribution – filtering and mitigating loops
This post is about route redistribution and the different filtering techniques we have available in our toolbelt. This post requires that you have a basic understanding of route redistribution. For some good posts look at Petr Lapukhovs posts at INE.
OSPF Vol1 finished
Finished OSPF Vol1 tonight. I should know pretty much everything about OSPF by now. Here are some advice that I think is good when handling OSPF. show ip ospf data self-originate – Will show what LSAs the local router is
RIP timers
RIP timers are the most basic thing in the world right? Even the command to set them is named timers basic… However in some documentation it is not really clear what the difference is between the invalid and holddown timer.