Route Redistribution- Part 4

ccie r/s ccnp r/s Nov 29, 2018

This post is the fourth in a series of posts on route redistribution. If you haven't yet read the first three, here are the links:

Up until now in this series, we’ve seen the need for route redistribution, looked at a basic configuration, saw how we could filter specific routes from being redistributed, and learned how to prevent a routing loop by tagging redistributed routes. In this final route redistribution post, we want to check out route redistribution with IPv6, and how that configuration varies a bit from what we’ve done previously with IPv4 networks.

Consideration #1 - The Redistribution of Connected Networks

First, consider a router running a routing protocol; let’s say it’s OSPF in this instance. Also, let’s say that router has several interfaces that are participating in the OSPF routing protocol. On that same router, imagine we’re running...

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Route Redistribution- Part 3

ccie r/s ccnp r/s Nov 06, 2018

 

This post is the third in a series of posts on Route Redistribution. If you didn’t yet read the first two, here are the links:

So far in this series, the route redistribution examples we’ve worked through used a single router to do all of the redistribution between our autonomous systems. However, from a design perspective, we might look at that one router and realize that it's potential single point of failure.

For redundancy, let’s think about adding a second router to redistribute between a couple of autonomous systems. What we probably don’t want is for a route to be advertised from, let’s say, AS1 into AS2, and then have AS2 advertise that same route back into AS1, as shown in the figure. 

The good news is, with default settings, that probably won’t be an issue. For example, in the above graphic, router BB2 would learn two ways to get to Network A. One way would...

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Route Redistribution- Part 2

ccie r/s ccnp r/s Oct 30, 2018

In a previous post, we considered the need for route redistribution, and we also took a look at some configuration examples. This posts builds on that previous configuration and discusses how we can filter routes using route maps.

Specifically, the previous example performed mutual route redistribution between EIGRP and OSPF, where all routes were redistributed between the two autonomous systems. However, some design scenarios might want us to prevent the redistribution of every single route. One way to do that filtering is to use a route map.

For your reference, here’s the topology we’re working with:

Screen Shot 2018-09-14 at 1.14.46 PM.png

Also, with our current route redistribution configuration, the IP routing table on router R1 looks like this:

Let’s say, for some reason, we don’t want the 192.168.2.0 /24 network redistributed from EIGRP into OSPF. One way to do that filtering is to use a route map that references an access control list (ACL).

First, let’s go to router R2 and...

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Route Redistribution - Part 1

ccie r/s ccnp r/s Sep 25, 2018

Introduction to Route Redistribution 

Until there is one routing protocol to rule them all, there is a need to have multiple routing protocols peacefully coexist on the same network. Perhaps Company A runs OSPF, and Company B runs EIGRP, and the two companies merge. Until the newly combined IT staff agrees on a standard routing protocol to use (if they ever do), routes known to OSPF need to be advertised into the portion of the network running EIGRP, and vice versa.

Such a scenario is possible thanks to route redistribution, and that’s the focus of this blog post. Other reasons you might need to perform route redistribution include: different parts of your own company’s network are under different administrative control; you want to advertise routes to your service provider via BGP; or perhaps you want to connect with the network of a business partner. Consider the following basic topology.

  

In the simple topology show above, we’re wanting OSPF and...

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5 SDN Concepts You've Gotta Know

ccie r/s ccna r/s ccnp r/s Nov 28, 2017
 

I recently did a Facebook Live session covering 5 major Software Defined Networking (SDN) concepts. If you missed the live session, or just want to watch a replay, check out this video.

We cover:

  1. Intro to SDN
  2. Python Installation
  3. Basic Python Programming
  4. Configuring a Router with Python
  5. APIC-EM Applications

BONUS: I'm offering viewers of this video $50 off my Fundamentals of Network Programmability video training series. That means, you only pay $147, as compared to the regular price of $197. To get your $50 discount, click HERE.

Enjoy!

Kevin Wallace, CCIEx2 (R/S and Collaboration) #7945

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OSPF Route Filtering

ccie r/s ccnp r/s Nov 14, 2017
 

Let's say you have one or more IP routes that you don't want appearing in a router's IP routing table. The reason might be for security or for router performance, as a couple of examples. With OSPF, there are three primary ways to accomplish this route filtering:

  • Filter a route coming in from another autonomous system, as part of a redistribution configuration.
  • Filter a route between areas, using a filter list.
  • Filter a route from being installed in an single router's IP routing table, using a distribute list.

This video discusses these three approaches, and it demonstrates the configuration of two of these approaches (because redistribution is a topic unto itself).

Enjoy the video!

Kevin Wallace, CCIEx2 (R/S and Collaboration) #7945

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Configuring Quality of Service Using MQC

The Need to Know MQC in a World of Automation

These days, Quality of Service (QoS) can be configured relatively easy. If we’re using the APIC-EM as a network controller to manage our routers and switches, we can simply point and click our way through the EasyQoS utility and have a very robust QoS configuration applied to our devices. Even at the command line interface (CLI) of a router a switch, we could invoke the power of AutoQoS VoIP (to optimize QoS settings for voice traffic, or (just on routers) AutoQoS for the Enterprise (to discover network traffic patterns and create a customized QoS configuration to reflect our network’s specific characteristics).

However, what if you need to make an adjustment to such dynamically generated QoS settings? If you examine the underpinnings of any of these QoS automation tools, you’ll see they all use the same approach to configure most (of not all) of their QoS settings. This approach is called Modular QoS CLI, or MQC for...

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Fundamentals of Auto Smartports

ccie r/s ccna r/s ccnp r/s Sep 26, 2017
 

The Auto Smartports feature available on Cisco Catalyst switches allows a port to automatically detect that you’ve attached a device it can recognize (e.g. a Cisco IP Phone, wireless access point, video surveillance camera, etc.)

Then, it runs a macro on that port to apply a "best practice configuration," including QoS, STP, and security settings.

This video introduces you to this exciting feature and gives you a configuration demonstration.

For scaling automatic configurations beyond a single switch, check out Cisco’s Software Defined Networking (SDN) solutions. In fact, you can sign up for my Free SDN Mini-Course by clicking HERE.

Kevin Wallace, CCIEx2 (R/S and Collaboration) #7945

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BGP Route Reflectors

ccie r/s ccnp r/s Aug 15, 2017

A BGP-speaking router, by default, will not advertise an Internal BGP (iBGP) route to an iBGP neighbor. One solution for this issue is to create a full mesh of neighborships within an Autonomous System (AS). However, that approach doesn’t scale well.

A more scalable solution is to use a BGP Route Reflector. That’s the focus of this new video I created for you. You’ll see the issue BGP has with iBGP-learned routes and how to overcome that issue with a BGP Route Reflector configuration.

Enjoy the video!

Kevin

Kevin Wallace, CCIEx2 (R/S and Collaboration) #7945

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Understanding EIGRP Part 6 (Router ID and Neighborship Requirements)

ccie r/s ccna r/s ccnp r/s Feb 23, 2017

This blog post wraps up our series on Understanding EIGRP by discussing two final topics:

  • The EIGRP Router ID
  • EIGRP's Neighborship Requirements

Let's begin our discussion by considering the EIGRP router ID.

EIGRP Router ID

Each EIGRP-speaking router has an associated EIGRP router ID (RID). The RID is a 32-bit value written in dotted decimal format, like an IPv4 address. A router’s EIGRP RID is determined when the EIGRP process starts. Interestingly, EIGRP uses the same steps to RID calculation as does OSPF. The following list identifies these step, in sequential order:

Step 1. Use the configured RID value (using the eigrp router-id rid EIGRP router configuration mode command).

Step 2. If no RID is configured, use the highest IPv4 address on a loopback interface in the up/up state.

Step 3. If no loopback interface is configured with an IPv4 address, use the highest IPv4 address on a non-loopback interface.

Interestingly, while EIGRP requires a router to have a RID, the...

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