Category Archives: Network 101

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Access Layer – New Switches and Cleanup…Finally!!

In our corporate office, we have a rather large IDF feeding multiple floors. It’s not my ideal setup, but it was here long before I got here, and it’s grown over the years. And it’s become a bit of a mess…a thorn in my side and something I’ve long wanted to clean up…but just never made the time. Well now we have made the time, due mainly to the end-of-life of the existing (8) 3560 switches (three switches in the rack 1, three in rack 2 and two in rack 4). Here is the ugly “before”…

Such an embarrassing mess...

Such an embarrassing mess…

We stayed late Friday evening and ripped everything out…and I mean everything. We installed 8 new Cisco 2960-X switches, all stacked as a single switch. Nice!! We also installed additional vertical and horizontal cable managers, and had all new CAT 6 patch cables in various lengths to reduce clutter. What a difference it makes…

Ahhh...much better!

Ahhh…much better!

We started the project right at 5:30 PM, Friday evening, which works well as employees wanted to get home! And we finished at 1 AM. Not bad at all. For verification, we walked almost the entire building, checking that everyone’s Cisco phones were booted up and properly registered. One of us will be at work early Monday morning just in case we missed anything.

Having a clean and organized cabling infrastructure pays off big in terms of easier maintenance and troubleshooting. Trust me!

Don’t Forget to Clear the Router Reload

So, I had to make some changes on the router at our DR (Disaster Recovery) site, located in another state. As I posted about before, setting a “reload in” command can save your bacon if you make a configuration mistake and get locked out of the router. So I did. And then I made all the changes, tested everything, and saved the config. Job well done. I logged off and started working on something else, but I had this nagging feeling…did I forget something? No…I don’t think so. Then it hit me…the router was going to RELOAD shortly, if it hasn’t already.

I quickly logged back into the router (it was still up), and I got this upon login…

Just in the nick of time

Just in the nick of time

Whew…I still had 7 minutes before the reload would have kicked in. As you can see, I cleared the reload, and breathed a sigh of relief.

What did I learn from this? Geez…I don’t know…that I’m getting old? Yep…I guess I am.

Outside Plant Cable Replacement Project – Part 2

Here is the followup to my post on Friday concerning the 100 pair feeder cable replacement. Things went very smoothly, for the most part. There were some issues, but we handled them as they came up, and we finished the project by 3 PM Saturday afternoon.

My main area of concern was removing the old 100 pair cable and getting the new 50 pair cable successfully installed. Most of the conduit is 4″, but there is one 400 foot section that is only 2.5″. With both the 100 pair and fiber installed, there is no way we can get the 50 pair installed first. We needed to remove the 100 pair to make room, which means cutting the 100 pair, and that means no going back.

So we did get the new cable installed from the main building through the first two conduits (all 4″), prior to making any cuts on the old cable. Here is a picture of a pullbox mounted on the side of the main building…note the yellow pull rope already installed. That was nice of the previous vendor many years ago. However, we used the pull rope to install mule tape, which I like better…it doesn’t stretch, plus it is more resistant to creating heat which could burn through any existing cable, such as the fiber Internet circuit (that would not be a good thing at all).

100 pair cable and yellow pull rope

100 pair cable and yellow pull rope

The next section was the 2.5″ conduit….we then cut the 100 pair cable on both ends of the conduit, and pulled it out (and used it to pull in a heavy duty mule tape). We then pulled in the new cable with no issues. There was just one section of 4″ conduit left to go, which went quickly. We ended up getting the entire cable installed Friday evening. Here is a picture of the spool of new cable, and one of the vaults along the path…

Cable spool and vault

Cable spool and vault

Here is a closeup of the spool hanger, which makes everything MUCH easier…

Spool hanger up close

Spool hanger up close

Saturday was termination and testing, which my vendor completed around 1 PM. I then had to move any phone lines that had been terminated on pairs 51 – 100 of the old cable, since they no longer existed. After that, I then tested every single line and the PRI circuit, and verified proper operation. No issues were encountered. I’ll return on Monday to complete my documentation and a bit of remaining cleanup.

And yes, I am breathing a good bit better today…

Outside Plant Cable Replacement Project – Part 1

Yes, I’m back. Sorry for the long absence…I’ve been swamped with a variety of life events, some good and some not so good. Yet in all things, to God be the Glory.

So, what is outside plant (OSP) cable? Well, it’s cable designed to be outside (or perhaps underground), exposed to the weather. The copper or fiber strands are surrounded by a very thick and hard plastic covering, and certain types of OSP cable contain a jelly filling, which would ooze outwards in the event of a tiny hole and not allow water in. Very cool.

At one of my remote sites, we have a 100 pair copper cable that feeds both data and voice services to another building about 1500 feet away. This cable was installed many years ago, and has a number of splice cans along it’s path. Over the last year, the cable has deteriorated substantially, and keeping the many analog lines up and running is almost impossible. (This site is still a large user of faxes and modems.)

Here is one of several pull boxes located along the path…note the conditions of the vault and the splice can located on the right side…

Wet and muddy pullbox

Wet and muddy pullbox

So I hired a vendor to remove the entire 100 pair cable, and install a new 50 pair cable in one long continuous feed, no splice cans at all. The vendor is also going to clean out all of the vaults and layer in some gravel to aid in drainage. We start at 3 PM this afternoon, working until sunset, and will return tomorrow morning. We hope to have the whole project completed by Saturday afternoon.

Some of you might be wondering why I’m going with a smaller, 50 pair cable, and not another 100 pair. Well, the 100 pair cable was installed way back when every desk phone required it’s own pair of copper. Back then, all of the phones were fed through this 100 pair cable. Plus we had multiple T1 circuits for data needs too. Now, though, our phone system is Cisco VoIP, which is handled via the data network and a single PRI circuit, plus the data T1’s have been replaced by a separate fiber network, so the need for 100 pairs is not there, and will never be there. A 50 pair cable is smaller, cheaper and easier to pull, and it will give us plenty of spare pairs if our needs grow.

I will take pictures of the process and will let you know how it goes in a couple of days. Have a great weekend!!

Using the RELOAD Command to Prevent Lockouts

There are two types of Network Engineers…those that have locked themselves out of a router and those that will. I am in the former group. If you do this long enough, so will you. How to prevent this? You can use the RELOAD command to schedule a reload should you get locked out. I made use of this feature earlier today, just in case.

I had to reconfigure a router at our DR site (Disaster Recovery) due to some IP address changes, and this involved both re-configuring the VTI tunnel interface and the main access-list. (Oh, and the router is located out of state.) This is just ripe for accidentally locking yourself out of the router should you mistype an ACL entry or add an entry in the wrong order. Let’s look at the options for RELOAD…


Viewing the options for the RELOAD command

As you can see there are several options. My changes would only take about 5 minutes to input so I decided to configure a reload in 10 minutes…

Configuring the reload for 10 minutes out

Configuring the reload for 10 minutes out

To review the reload status, simply do a “show reload”…

SHOW RELOAD to view status

SHOW RELOAD to view status

I also added a reason for the reload, so if someone else logged into the router they would know the “who” and the “why” for the reload. They would see something like this…

RELOAD status for other users that might connect into the router

RELOAD status for other users that might connect into the router

Now you can proceed with the configuration changes…just don’t save the configuration, at least not yet. If you do get locked out, then wait just a bit. The router will reload and come back up with it’s original configuration, and you can connect right back in and try again. I have used this many times, and it has saved me on more than one occasion.

After you have successfully made your configuration changes without getting locked out, then you can cancel the reload…

Canceling the reload

Canceling the reload

Hope this helps!  (And don’t forget to save your changes!!)

What Is – DHCP

DHCP – Dynamic Host Control Protocol

This is a wonderful and time saving little protocol. You already know that every device on a network has to have an IP address…but…how do you configure all of those devices and their IP address? Well, you could do it manually. Once. Twice. Maybe several times. But you would quickly realize the manual way is a pain in the butt….there has to be an easier way! Well, there is. Enter DHCP.

When you turn on most devices, as they boot up, they send out a packet onto the network basically saying “Help…I’m booting up and I need an IP address. Can anyone help me?” And if you have a server (or other device) running a DHCP process, then the answer is yes. The DHCP server will reply with an IP address, and several other bits of needed information, and just like that…the device has an IP address and can start communicating on the network.
Isn’t that cool? I think it is. I will post more about DCHP in the near future and we will see exactly what goes on during a DHCP request.

Network Problems and Mondays – What Gives??

I just have to ask this question…what is it about computer networks and Monday mornings? I can’t believe how many times I have arrived to work on a Monday morning, and I already have one (or more) tickets assigned to me concerning network issues at various sites. Everything was working just fine Friday afternoon when I left. What happens over the weekend? Do little network gremlins invade my network over the weekend and create issues just to irritate me on Monday? I guess the answer is yes.

Today’s issue was at one of my companies temporary offices, housing just four workers. They were using a plain Internet circuit terminated on a Linksys firewall, and they couldn’t connect to the Internet or to the companies VPN. Since the office was close by, I ran over there and after a bit of sleuthing, found that the DHCP process had stopped working on the Linksys firewall. (It had stopped handing out IP addresses to the end users.) A reboot of the device solved that problem.