Category: Networking

Cisco SD-WAN ISR 4k Getting Started – Part 1 – Upgrading Code

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Upgrading from IOS-XE to SD-WAN Code

Recently I was building out a lab to iron out a migration onto the Cisco SD-WAN (Viptela) solution. As part of that process existing ISR 4k routers were going to be used at the edge devices. This process, while fairly straight forward, came with a few “gotchas” and “snags” that I had to work through. In this post I will cover the upgrade of the ISR onto SD-WAN code. In the next post I will cover the bootstrap process as well as a couple of caveats related to vManage and the ISR4k routers.

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Remote Troubleshooting Crossed Fiber Using Port Channels

Reading Time: 5 minutesLast year I was involved in assisting a datacenter core and access-layer refresh. In this case the IDF’s were reusing existing fiber patches and the run to the datacenter stayed in place. however, within the datacenter core equipment was placed across the room required new cross connects to be ran to the new core cabinet. When the cutovers began to take place the IDF’s were spread out over a large campus. Meaning troubleshooting by walking back and forth to check cabling was extremely time consuming and inefficient. Since all the IDF’s were connected via port channels I was able to figure out which runs were crossed and go fix them all at once using only the ether channel show output. I’ll walk you through the process now.

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Cisco Champions 2017 – A reason to reflect

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tl;dr – THANK YOU ALL!

Yesterday morning I opened up my Spark app and was surprised to see I was added to the Cisco Champions room. I checked my e-mail and saw nothing. I knew it was being announced soon do to some twitter chatter. After validating with members it was true. I was selected as a 2017 member of Cisco Champions. I’m going to say I’m blown away even still today. I am absolutely honored to be part of such an amazing group of individuals. It has caused me to sit back and think about how I even came to know the people I look up to. So how did it start?

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Bulk enable PIM via TCL

Reading Time: 3 minutesI’ve been working on doing some multicast labs lately and am constantly resetting my lab devices to their default configs and starting from scratch. As many of us know, to enable PIM on all of your interfaces you must go into each interface and enable it manually. There is no default command to enable PIM on all interfaces. We know PIM should be enabled 1 to 1 with interfaces involved in routing making this a boon. With that in mind, and the fact that I am rather comfortable with the concept of needing PIM on the interfaces, and likely speak and type this command in my sleep, I decided to make it easier and modify a previous TCL script I had written to enable PIM on every interface that has an IP address assigned to it. With the great “Send to Chat” feature of SecureCRT I can do this across my entire topology on one fell swoop. In a real world environment, you could use a tool like Solarwinds to push this out to your devices.

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Apps for a Network Engineer Part II: Windows

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Windows for Network Engineers

Part two in my series of apps for network engineers across the three major platforms. I previously did the post for Mac when I first refreshed my laptop and purchased my first new Mac in 8 years. Issued by work, my daily laptop is a Windows machine which is fine with me. I would prefer to use Mac but give me a machine that has the tools I need and I’m fine. So with that in mind, I am going to list my favorite Windows tools for Network Engineers.

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Route-Targets Explained

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As I began to study MPLS L3VPNs I was excited to start flinging my fingers around the keyboard. However, I ran into a little snafu during my learning. All of the videos and configuration example I was finding didn’t separate the difference between the Route Distinguisher (RD) and the Route Targets. Most of the examples simply matched the RD to the Route Targets and/or used the same Route Targets for both import and export. This left me feeling like I wasn’t really understanding what those commands and numbers were accomplishing. I decided to make a visual representation to make it easier to understand.

Router-Target Policy Visualization

Router-Target Policy Visualization

To make this concept easier to understand we first need to know that the RD does not dictate what routes a route will import or export into it’s PE-CE routing process. The purpose of the RD so to add an additional label to prefixes so overlaps can be inserted in the BGP table and shared amongst the various PE routers. For example, my RD of 65000:8 indicates any routers in the BGP table from my customer vrf would indicate a prefix of 10.20.30.40 as 65000:8:10.20.30.40. This means if another vrf with a different RD of 4242:42 could also install 10.20.30.40 in the providers BGP table as 4242:42:10.20.30.40.

Now that we are clear on the use of the RD we can move onto the Route Targets. There are two route targets we define in our VRF policy. The import and export targets. Many examples and videos show these as the same (which is a perfectly valid configuration) often times matching the RD. To clarify exactly what they are used for I have used three different Router Targets. I am going to correlate their indicators with colors to make the example easier to visualize.

Routes exported from the headquarters use 30:8 which we will call the “Blue Routes”
Routes exported from Branch 1 will use 10:8 which we will call the “Red Router”
Routes exported from Branch 2 will use 20:8 which we will call the “Green Routes”

This exporting is done by the PE routers connecting to the CE routers. The CE routers in this example our peering via eBGP with the PE routers inside of a VRF. The VRF configuration on the PE routers is what indicates the Router Target identifier to export. At this point we can write a policy of which routers should be allowed into the individual CE routes using the VRF Route Target import. Lets follow a case from the HQ to Branch 1.

HQ CE peers with its PE router which has a VRF policy stating to export its routes as the color Blue. These routes are passed around to the other PE routers. When the Branch 1 PE peer receives the routes it sees that it’s VRF policy is stating to export its routes as the color Red as well as import any routes that are colored Blue. Back at the headquarters we have our VRF policy set to import both the Red and Green routes. Branch 2 does the same as Branch 1 but swapping out Red for Green.

By writing the VRF policies this way we have created a Branch to HQ connection while not passing routes Branch to Branch. In my diagram I show the routes coming into the CE routes as it is the ultimate end goal however, please keep in mind that the VRF configuration is done on the PE routes.

I hope that by using simple colors for the routes it has simplified the reasons we use the RD, and the import and export Route Target. I found it difficult to understand the true use of these configuration when they were using the same value for the RD as well as the import and export Route Targets.

 

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Synapps Paging Delays – An HTTP/TCP Wireshark diagnosis

Reading Time: 5 minutesThe Scenario goes like this: A Synapps – SA Announce paging and messaging server integrated with Cisco’s CUCM hosting around 30 phone to phone paging groups. The paging had been working fine for months and out of no where one of thirty particular groups was putting in multiple trouble tickets over multiple days that the paging isn’t working.

So begins the troubleshooting and diagnosis. My first action was to monitor the paging server as it has a real time display of who is calling a paging group and which group they are calling at in given time. When I was monitoring this I could see multiple people calling multiple groups including the one in question. So this brings up one of those “what gives” questions. Are they just doing something wrong up in the area. Time to take a trip and raise that pedometer count.

I arrive in the area and try and locate and area where I can visually see and hear multiple phones. Easier said than done but in this case I was the only one available to work on the issue and knowing that the paging server will activate the speakerphone and mute lights when a group the phone is a member of is called this was my best bet and understanding what was going on. After making my first test page I can see that lights on the phones I can see are immediately lighting up, however I can’t hear audio. As I stand there dumbfounded with the phone still off hook all of a sudden the audio starts picking up the background noise. However, paging shouldn’t have a 6 second delay before you can start talking. Six seconds is a long time to wait after hitting page to start talking. So whats going on? It’s only one group experiencing this. What is different about their group? Time for a deep dive in the diagnostics world. Enter Wireshark.

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Trouble shoot with TDR

Reading Time: 5 minutesThis article is another example of trouble shooting by putting multiple pieces together. While it relies upon existing knowledge of the environment in which the article is based it should prove to be a good example of a trouble shooting process that will hopefully be able to spark some creative thinking the next time you have a problem that needs to be resolved.

The scenario starts out with a user ticket stating that the phone isn’t working. After some fact gathering the below details and possible solutions were outlined.
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Apps for a Network Engineer Part 1: MAC

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MAC for Network Engineers

I am not going to play bias in anyway towards any particular apps. I’m surely not going to get into the debate between Windows or Apple as a primary computer. In fact, I’ve spent the last 4 years using Windows exclusively for work due to work issued laptops and the lack of support for Mac in the companies I have worked with. However, I recently purchased a new Mac to get back to what I personally like best, with that, I had to rebuild my app repetoir for doing my job on a Macbook. This took some digging and searching to find apps similar to what I used on Windows. I’m still searching for all the app alternatives but I figured I could make this into a working document of my favorite apps in terms of network engineering.

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Tracked Static Default Route

Reading Time: 6 minutesAs common place in today’s networks redundancy is key. Applications are the key components to business obtaining revenue. More and more applications are becoming SaaS and ecommerce is here to stay. With that being said, many companies are moving to redundant connections to the internet. These connections could be through two different ISPs, or both connections to the same ISP. Often times these connections will be of different speeds to save on costs. The key to these connections is to maintain internet connectivity.

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