Archive for March, 2010

Mar
31

For many of you geeks and nerds out there like me (I’ll take a poll as to which one is better at another time), you’ve worked with some *NIX flavor for many years now. For others of you, you have most likely dabbled with various Linux distro’s and have come to know commands as needed. One extremely powerful tool that you may or may not have come across during your years is SED or the Stream Editor (sometimes referred to as the String Editor as well). This tool can take input from stdin and manipulate it as it leaves via stdout.

For those of you that have used SED in the past, you will certainly notice some similarities to the Cisco set of commands known fondly to many voice folks as Voice Translation Rules, and given your ability to pick out the differences, may help you in your quick adaptation to Cisco’s iteration of this tool.

For those of you that have not ever used this tool, take no worry. For in these next series of blog posts I will attempt to break down not only the components of Voice Translation Rules, but of the overall science of Digit Manipulation in IOS, into bite-sized chunks that will help you to digest it much easier. Continue Reading

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Mar
28

Embedded RP, with IPv6 multicast, is a very cool trick. It simply embeds the RP IPv6 address as part of the multicast group address. This way, when a multicast router sees the group address, it can extract the RP and begin to use it for the shared tree immediately. The only thing that has to be hard coded on a router is to tell the RP that he is the RP, and that’s it. All the other routers in the network dynamically learn the RP address from the group address. So here is the problem: A 128 bit RP address can’t be embedded into a 128 bit group address and still leave space for the group identity, (at least not without compression).

You may want to visit the 2 previous posts on IPv6 multicast using static RPs using this link, or BSR mapped RPs using this link.

Here is the topology we are using, which matches the one from the previous posts:

IPV6 Multicasting

To facilitate the embedding of an RP address int the multicast group address, Continue Reading

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Mar
27

In a word, “Way to GO” (without the spaces, that would be one word :) ). I am impressed at all the feedback and ideas we received regarding the IKE phase 1 riddle we posed last week. You can read the original post here. Ideas were creative and varied.

As one of our INE Instructors say, “If there are 2 different ways to configure something, as a CCIE candidate, you had better be prepared to know all 3 “.  If you would like to see “a solution”, read on. Continue Reading

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Mar
25

Since IPv6 multicast doesn’t support the Auto-RP process like IPv4, there must be other methods for dynamically configuring a RP. The two options are using Bootstrap Router (BSR) and embedded RP. In this post, we will walk through BSR, step by step together.

For BSR to work, we need to have at least 1 candidate BSR router, and 1 candidate RP. For fault tolerance, we would want to have at least 2 of each.   If a RP was on the network, but is powered down, I suppose that would make it a “Lost Candidate”.  :)
To understand the process, let’s watch it in action. We will use the same diagram that we did in the previous blog post. (To see the details of the topology and an example of static RP, please visit the original post).

IPV6 Multicasting

First, we will configure a couple routers as BSR candidates. Continue Reading

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Mar
24

In the earlier article titled EEM demystified, we took an introductory look at the basic format for EEM applets, and some basic samples for general operation, including some basic CLI command usage, getting input, and displaying output.

In this article, we are going to take a look at some of the additional actions available, specifically looking at variables, a few operators, and some general conditional structures.
Continue Reading

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Mar
24

IPv6 multicast routing is a fun topic, and is often either loved or avoided :) . Here is a jump-start for all my CCIE candidate friends.

Readers digest version: “Auto-RP is out, Dense-mode is out, IGMP is replaced with Multicast Listener Discovery (MLD). MLDv2 supports SSM. RPs, Bi-directional PIM, SSM, ASM and BSRs are still alive and well, and we can now avoid static RPs and BSR if we choose to use embedded RP within the multicast packets themselves. (Crazy and amazing stuff).

Want a little more? Then read on. In this multi-part blog, we will discuss static RP, BSR, and Embedded RP. This first blog will discuss static RP, with some examples that will assist you in getting started.  For those of you who subscribe the open lecture series, I will be including all three RP options in a discussion there as well.

Here is the topology we will use:

IPV6 Multicasting

Here is some additional info on the topology. Continue Reading

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Mar
23

This blog post is taken from the INE Resources area Understanding Frame-Relay Traffic Shaping presentation by Brian Dennis.

Overview

Frame-Relay traffic shaping is designed to control the amount of traffic the router sends out of an interface or out of a particular DLCI. Common reasons for Frame-Relay traffic shaping are:

  • It allows the router to conform to the rate subscribed with the service provider
  • It allows for the throttling of a higher speed site (768K) so that it does not overrun a lower speed site (64K)

Traffic shaping is designed to delay excess traffic, whereas policing is designed to drop excess traffic.

Terminology

  • Available Rate (AR) – the actual physical speed of the interface; on a DCE serial interface this is determined by the configured clock rate. On a DTE serial interface, it is determined by the received clock rate. A router will always (by default) try to send out at the AR regardless of the interface bandwidth. AR is also commonly referred to as port speed, line rate, or access rate.

Continue Reading

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Mar
22

One of our students asked me for a concise example of SNMPv3. James, here you go!  This blog has examples and explanations of the features used in SNMPv3.
Older versions of SNMP didn’t provide all the features of SNMPv3. V3 supports a User-based Security Model (USM) for authentication, and a View-based Access Control Model (VACM) to control what that user account may access.  Of course the user accounts don’t represent end users, they are just the configuration elements we configure on the SNMP devices, primarily for creating the connection to or from the SNMP device.

With version 3 we may use the following methods:

  1. noAuthNoPriv: requires username, but no MD5 validation of that user, and no encryption
  2. authNoPriv: requires username, provides MD5 validation, but no encryption
  3. authPriv: You guessed it. Requires username, uses MD5 validation, and encrypts too. Continue Reading

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Mar
21

Bob took a moment to reflect back, and realize how far he had come over that past several months. He smiled to himself as he remembered how much he has learned about the technologies of  DMVPN, the ASA Firewall and IPSec, including GET VPN.

He had also improved his skills in MPLS, Multi-Protocol BGP, IOS IPS, EEM, and many other areas by using the sweet blog articles at INE.  (Shameless Plug :) ).

One Monday morning, as he was feeling refreshed from a rare weekend of no support calls, he was met by one of his co-workers with a technical riddle. Bob thought about it, googled it and then attempted to lab up a few solutions, all without success.

Your mission, should you choose to accept it, is to assist Bob by identifying the possible solution(s) to use IKE PHASE 1 in the desired way. Continue Reading

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Mar
20

A pretty important topic that is very easy to overlook when studying multicast is the PIM Assert Mechanism.  After working with the TechEdit Team in the IEOC it is obvious that more than just a handful of students are confused about what this mechanism does and how it works. In this blog post (the first of many dedicated to multicasting), we will examine the PIM Assert mechanism and put this topic behind us in our preparation in mastering multicast.

In Figure 1, R1 and R4 have a route to the source 150.1.5.5 (the multicast source), and share a multi-access connection to R6. R6’s FastEthernet0/0 interface has joined the multicast group 239.6.6.6.

Figure 1

Figure 1

Continue Reading

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