Sunday, April 29, 2012

Lessons - Newbies

I was thinking the other day, what lessons need to be learned by everyone who wants to have a career in networking.
This topic comes up in a lot of different places, I've seen several articles over at related to getting started and changing gears. I think about this a lot as I have students who have networking in their major, who work for the IT department, have some weird questions. We have a Cisco Academy, which the lab is on the other side of the wall from my cubicle.

So lets start with the list, in no particular order:

  • Operation of Spanning Tree Protocol - I get yeah it prevents loops by.... What does it do when it is off and you put the loop in the network? What happens to a router which is setting up a vpn tunnel and looking for traffic from the lan to build that tunnel and you put a loop in the network? (Short answer: NO Tunnel) My last post was about STP:
  • 802.1Q operation between switch vendors, not everybody configures like Cisco.
  • You will forget to save the config at some point, especially if you have multiple vendors gear - see point above.
  • Shutting down the wrong interface - ie the one that connects you to the equipment, learned that one very early, had to walk across campus to fix my error.
  • RTFM - Read Read Read, then ask questions.
  • Multicast operations - because it is in use in a lot of places that you may not realize. Avaya One-X Quick Edition phones use it to save voice mails  between all the units on the network.
  • Your gonna fail, learn from it
  • Know the difference between a hub and a switch - use the terms correctly
  • Any business, bigger than a 50 people probably has more than one subnet / vlan. That means that you can not just plug any cable into any switch port, as a rule.
  • Structured Cabling is there for a reason, keep it neat. (I'm still working on this at times, past sins)
  • If you encounter one of these:  It takes two cables to complete the patch. Switch to mid-span , mid-span to patch panel. See RTFM - the ports are labeled.
Avaya Mid-Span

So lets put this one in the bag... We are all still learning, keep an open mind. These are some of the things I see or have done. 

Disclaimer: This may be disjointed post, but I needed to get it out. Comments are welcome. 

Wednesday, April 18, 2012

Spanning Tree - STP - Love it & Hate it

So every network engineer I talk to seems to have the same relationship with Spanning Tree. The love it when it works and hate it when it works. Spanning tree is used to prevent loops in the network. Link to Read more, as I will not explain the whole thing here.

When I posted the following picture on twitter, it generated some chatter.
What??? That could be a problem. Especially since those are both loops. Now if these are both cabled to two ports on the same switch and STP is on, one of the ports will go into blocking mode. If STP is off we have a loop and then we have lost all control. Which should be a lesson for these younglings in which they have to learn. This lesson is best taught in multi-vendor networks as there are different default settings for STP between vendors.

This picture was taken in the Computer Science Networking Lab. Two things about the lab from my prospective:

  1. I give them a single feed to the rest of the network, one vlan and a small dhcp scope in which to make things easy on them (There is more address space for them to use outside the scope, use at their own risk) 
  2.  Any problems I have in which the rest of my network is threatened, shutdown their feed.

Now back to the photo, is STP in play, is there a loop? 

No loop! except in the cable. Each jack in this case represents a different rack, so the wall plates are "stations" to work at. This keeps the younglings from stacking onto of each other doing labs.

This is the way they chose to bring production network to the other side of the room to the lab rack. This was done by our Cyber-Defense team, last year's team can be found here.  

No worries on this one but it is right inside the door and makes me double-take every time I see it.

Thanks to all that responded to the post on twitter. 

Saturday, April 14, 2012

Avaya IP Office - Time punch stations

For several years we have had ADP Handpunch time clocks for hourly workers to clock in and out. Several weeks ago they stopped working. The payroll person could not retrieve the data for the clocks. I kept getting ask if there was any network changes that would affect the clocks. No changes had been made, or so I thought. ADP tech support said it's a network issue, I said nothing had change these have been working for 4 or 5 years. Resetting the clocks would resolve the issue for a day or two. Al the while you can still ping the handpunch units.

During this time I was really trying to get a new Avaya IP Office unit ready to go out too one of our small offices. I had racked it in my test rack, hooked it to the network and went back to my desk to configure. This is about my 9 IP Office unit being deployed. If you are not familiar with IP Office units, configuration happens by pulling the configuration file and then pushing the changes back. So back at my desk I open the Manager software and discover the new unit.

No problems finding the unit and going about my day...

Back to the Handpunch issues, my coworker had been coordinating between the payroll person and getting a call setup with a higher level ADP tech support person. So we get the call with the tech and he starts running though all the same tests, Ping, trace route, handpunch diagnostics, etc. Out of the blue the tech asks do you happen to have an Avaya IP phone system. I hesitantly say " Yeah, why?" He explains that there is a UDP discovery method that Avaya uses which takes the handpunch clocks offline. I say well send me a document to show this. Which he did.

From Avaya IP Office Manager documentation

Preferences in IP Office Manager

So by unchecking the UDP Discovery on my copy of Manager, I was able to stop this behavior to the time clocks. Reset the time clocks and I haven't had this problem again.

So why did this cause a problem this time and not the hundreds of other times I have used the software to configure the units? When I racked it into my test rack and hooked it up, I connected it to the same vary large flat network in which most other administration machines and services are on. All my other phone equipment is on different vlans.

I hope that others that may run into this can find this information usefully, since I didn't find much when I searched on my own.

Friday, April 13, 2012


After having a few conversations on twitter with @amyengineer I've decided to post a few of my phone pictures.

100 pair entrance cable. - Splice case submerged
It has taken on water

The rest are pictures of my phone room and some of the equipment inside.

Splice Can - 300 pair cable to 3 - 100 pair cables

Demarc is beige box left-center

Avaya IPO 412 Left - Nortel Option 61C right

Power rectifier and batteries for the Nortel

Starting to Write

Ok, so this is my first post.

Why am I writing? Why does anyone? To convey ideas, thoughts, meaningless BS.