CCNP Recertification

Posted on Tuesday, 22nd November 2005 by sean

I’ve read and heard that there are some idiosyncrasities about connected routes and IS-IS when redistributing. Most recently while reading “Optimal Routing Design” and also when talking with a friend who was studying for the BCSI exam. When redistributing out of IS-IS, some routes are missing, notably connected routes. Let’s investigate. A simple three-router network: [...]

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Posted on Thursday, 17th November 2005 by sean

Build the Best Data Center Facility for Your Business Douglas Alger Cisco Press, 2005 Synopsis This book is a must for anyone in charge of a datacenter, be they building, expanding, or just running the operation. It provides a solid grounding in HVAC, electrical, layout, and other concerns. Working in IT, I’m quite familiar with [...]

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Posted on Monday, 14th November 2005 by sean

A simple one to get the posts flowing… BGP peer groups simplify the configuration of BGP neighbors by moving the template into a configuration. For example, look at R3: router bgp 1 no synchronization bgp log-neighbor-changes network 10.3.3.0 mask 255.255.255.0 network 10.50.0.0 mask 255.255.0.0 neighbor 10.50.0.1 remote-as 1 neighbor 10.50.0.2 remote-as 1 neighbor 10.50.0.2 route-reflector-client [...]

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Posted on Tuesday, 18th October 2005 by sean

Network Administrators Survival Guide Anand Deveriya Cisco Press, 2006 Synopsis A book covering the use of Open Source software to manage and document your Cisco network. Topics range from the traditional availablity and performance graphs, to more advanced security tools. The Book I was pretty happy when I received this book because a year ago [...]

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Posted on Thursday, 13th October 2005 by sean

Continuing on with route reflectors, here is an example. The specifics of the topology don’t matter too much. R0, R1, R3, and R6 are all in AS1 and happen to be sitting on the same LAN segment. R1 connects to R2 over a serial line, and R2 is in AS2. R3 is the route reflector, [...]

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Posted on Tuesday, 13th September 2005 by sean

Scaling Internal BGP can be a challenge. Every iBGP router must have a peer with every other iBGP router within an AS. Why? BGP uses the AS-PATH attribute for loop prevention. However, the AS is only prepended between eBGP neighbours, so it will never appear in iBGP. However, this means that you must configure n-1 [...]

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Posted on Friday, 2nd September 2005 by sean

Just finished an online lab through Cisco’s Learning Connection called “Advanced BGP Design with BGP Community Attribute – Challenge Lab – LabOps – IP – Accelerate (SE)” The CLC has a lot of labs, I look forward to doing more Start here: http://forums.cisco.com/eforum/servlet/PrepCenter?page=BigSnippet.PrepCenter.PrepCenter_freeTrial_learning_connection In this lab the object was to learn communities and route-maps. Basically [...]

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Posted on Tuesday, 2nd August 2005 by sean

Last week I started in on BGP Route Aggregation, used to reduce the number of routes advertised in the global tables and to increase stability. This article will look at fine tuning the advertisements sent out when using the aggregate-address command. First, I left off one method of advertising an aggregate, which is creating a [...]

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Posted on Tuesday, 26th July 2005 by sean

Route aggregation happens where multiple routes are rolled up into a series of shorter prefixes (ie 4 /24′s become a /22). The idea is to reduce the number of routes that need to be processed. Often, the specifics don’t matter. If I’m advertising the 4 /24′s as above and they all go the the same [...]

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Posted on Friday, 22nd July 2005 by sean

BGP receives path updates from its peers, and then makes a decision as to which route is best. This is the route that is potentially transferred to the IP routing table and advertised to peers. The synchronization rule also plays a part in this decision, and is investigated more closely. Cisco has the BGP Best [...]

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