Edit: Thanks for playing! You can find the official answer and explanation here. Read More

INE's long awaited CCIE Service Provider Advanced Technologies Class is now available! But first, congratulations to Tedhi Achdiana who just passed the CCIE Service Provider Lab Exam! Here's what Tedhi had to say about his preparation: Finally i passed my CCIE Service Provider Lab exam in Hongkong on Oct, 17 2011. I used your CCIE Service Provider Printed Materials Bundle. This product makes me deep understand how the Service Provider technology works, so it doesn`t matter when Cisco has... Read More

One of our most anticipated products of the year - INE's CCIE Service Provider v3.0 Advanced Technologies Class - is now complete!  The videos from class are in the final stages of post production and will be available for streaming and download access later this week.  Download access can be purchased here for $299.  Streaming access is available for All Access Pass subscribers for as low as $65/month!  AAP members can additionally upgrade to the download version for $149. Read More

Hi Brian, What is the major difference in using an E1 route over an E2 route in OSPF? From what I’ve observed, if you redistribute a route into OSPF either E1 or E2, the upstream router will still use the shortest path to get to the ASBR regardless of what is shown in the routing table. The more I read about this, the more confused I get. Am I missing something? Matt Hi Matt, This is actually a very common area of confusion and misunderstanding in OSPF. Part of the problem is that the vast... Read More

OSPF and MTU Mismatch Dear Brian, What is the difference between using the “system mtu routing 1500” and the “ip ospf mtu-ignore” commands when running OSPF between a router and a switch? Thanks, Paul Hi Paul, Within the scope of the CCIE Lab Exam, it may be acceptable to issue either of these commands to solve a specific lab task. However, it is key to note that there is a difference between ignoring the MTU for the purpose of OSPF adjacency and matching the MTU within a real production... Read More

This document is presented as a series of Questions and Answers, discussing various aspects of OSPF protocol designed to prevent inter-area routing loops and related issues. The discussion covers ABR functions, Virtual-Links, OSPF Super-backbone, OSPF Sham-Links, BGP Cost Community. Reader is assumed to know these concepts already, as this publication focuses on complex interaction features arising in MPLS/BGP VPN scenarios. The discussion is culminated by analyzing a number of issues arising... Read More

I enjoyed Petr's article regarding explicit next hop.  It reminded me of a scenario where a redistributed route, going into OSPF conditionally worked, depending on which reachable next hop was used. Here is the topology for the scenario: Here is the relevant (and working :)) information for R1. Read More

Abstract This publication briefly covers the use of 3rd party next-hops in OSPF, RIP, EIGRP and BGP routing protocols. Common concepts are introduced and protocol-specific implementations are discussed. Basic understanding of the routing protocol function is required before reading this blog post. Overview Third-party next-hop concept appears only to distance vector protocol, or in the parts of the link-state protocols that exhibit distance-vector behavior. The idea is that a distance-vector... Read More

This goal of this post is brief discussion of main factors controlling fast convergence in OSPF-based networks. Network convergence is a term that is sometimes used under various interpretations. Before we discuss the optimization procedures for OSPF, we define network convergence as the process of synchronizing network forwarding tables after a topology change. Network is said to be converged when none of forwarding tables are changing for "some reasonable" amount of time. This "some" amount... Read More

Hi Everyone! The Challenge People tend to underestimate the important of IGP routing features in modern network. So here is a small challenge scenario for you to practice OSPF traffic engineering. Take a look at the diagram below for information on the topology and link bandwidth. You may assume that every router has a loopback interface for network testing and OSPF router-id selection. There is a large cloud of media servers behind R4, and the users behind R1 need to use full 300Mbps of... Read More