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Cisco Systems is a major network technologies company. This tag identifies general information related to the company.

Service Config - Error opening tftp://255.255.255.255

Tue, 2013-02-19 21:31
Command Line

If you have worked on a newer Cisco IOS device, you may have seen the following error messages: 

%Error opening tftp://255.255.255.255/network-confg (Socket error)
%Error opening tftp://255.255.255.255/cisconet.cfg (Socket error)
%Error opening tftp://255.255.255.255/router-confg (Socket error)
%Error opening tftp://255.255.255.255/ciscortr.cfg (Socket error)

If you are wondering what these messages mean, it is the result of the config service being enabled by default in some IOS versions. Read on to learn about how it works and how to disable it.

Cisco 4500 Series Sup7e Install Notes

Wed, 2013-01-23 21:51

One of my projects at work is to replace a couple switches with newer (and larger) 4507R+E with Sup7e. I love projects like this because they're relatively straight forward, but mainly because they are fun! Who doesn't like unboxing a $60,000USD switch and firing it up? It's like a Cisco birthday or something.

Anyway, while configuring this thing, I've noticed a few quirks... idiosyncrasies? "Features"? Whatever you call them, they're new to me and I felt like blogging about it.

SD Memory in a Supervisor

First, just an observation: Cisco now has Secure Digital (SD) memory in a Supervisor. You might be thinking "yeah, I read about that when the Sup7e came out..." However for those who were in the dark, now you know. Here's a picture to share: 

Use the Configure Replace command to speed up your labbing

Tue, 2013-01-15 20:31

I've been labbing quite a bit lately, working on Narbik's R&S workbooks, and I've been rebooting my rack after nearly every lab to clear things out. Well, I was perusing the Interwebs and a forum post reminded me of the config replace command. Sheesh! I wish I would have remembered that a few hundred reboots ago...

Even though I knew about this command, and have even included it in a blog post or two in the past, I had forgotten about it since I wasn't using it all that often. So, just in case someone else out there has forgotten about it, I figured I'd do a quick write up demonstrating the command in action and hopefully jostle some memories (or just help me remember if I forget it again).

Here is a 1841 router that used to be R5, but I changed it's hostname to Testing and did a no shutdown on all it's interfaces. Follow the config below for the usage:

Cisco IP Phone Vulnerability Enables Remote Eavesdropping

Thu, 2013-01-10 23:20

A recent Cisco Security Advisory details a vulnerability that allows "an arbitrary code execution...that could allow a local attacker to execute code or modify arbitrary memory with elevated privileges." In other words, if you have a Cisco 7900 series IP Phone on your desk, it can be totally pwnd.

This might not come as a surprise to those who have worked with these devices or other IP phones with programmable features. It's basically a little computer with a plastic phone shaped box wrapped around it. If this is a surprise to you or if you don't believe it, check out the video demonstration below.

CCIE Boot Camp Review - Micronics (Narbik's) 12-Day

Mon, 2012-12-31 07:52

Studying for your CCIE? If you are, then you might be planning to take a boot camp to help you prepare. A lot of candidates use boot camps to help them prepare and there are many choices available to routing and switching candidates in particular. If you haven’t taken a boot camp yet and are still considering which one to attend or whether or not to attend one at all, then this blog post is written for you.

Save yourself some time with the default interface command

Mon, 2012-11-26 01:00
Command Line

If you configure Cisco equipment on a regular basis, you might find yourself in a situation with a large number of router or switch ports that need to be reconfigured. There are several ways you can prep your switch ports to complete your task:

  • You could do a "show run" and then build a script that includes the "no" form in front of each of the old commands, then apply your new script.
  • You could simply overwrite the old config with the new and then go do the no form of the stuff you don't want after the fact.
  • You could erase the startup-config then reload the switch and start from scratch (assuming the device isn't in production anymore).

There are probably another half dozen different ways of simply erasing the config and starting over, but there's one more option that this post is focused on today: the default interface command.

My journey to become a CCIE

Fri, 2012-09-14 05:31

I've been interested in technology for as long as I can remember. From my early beginnings of learning how to navigate the DOS command line interface on my dad's computer while he was off at work, to building my first PC (with 8Mb of RAM!). I've always had an interest and a knack for this stuff.

Over the past decade, my interest in networking technology has grown significantly. In 2001, I earned my CCNA while working at Cisco (on contract) and a few years later installed my first 6509 in a global financial company. Several certifications followed down the road including the CCNP and CCAI. I now teach Cisco curriculum part time while working as a Senior Network Engineer for a mid-size enterprise. My drive to learn has never stopped, in fact it just keeps growing the more I am exposed to this stuff.

The time has come to take it to the next level.

Several months ago I made the decision, after some serious research and discussions with my wife, to begin studying for the CCIE Routing & Switching Exam. I started by researching and reading everything I could find regarding the exam - Cisco's official exam page, other blogs that detail how they approached the exam, podcasts talking about the exam, etc. I spent a good month reviewing my options before I finally made the decision that absolutely, without a doubt I am going to go for it - no matter what it takes.

I've written this blog post to share my experience so far and hopefully help others in a similar situation to make the go-no-go decision.

End of Life announced for 3750/3560 G and E switches

Mon, 2012-07-30 08:01

Earlier this year, Cisco announced the end of sale and end of life for their 3750G, 3750E, 3560G, 3560E Catalyst switches. For some reason, I just received it in an RSS feed (not sure why there was a several month delay). But I figured I'd share the "news" since these are such a common platform.

The official end of sale date is January 30, 2013. As is tradition, support will be provided for 5 years following the last date of sale, so you have until 2018 for the last date of hardware support. If the Back to the Future movies hold any truth to them, we should have hover cars well before that date...

For reference, here's a quick list of dates:

Password Recovery on a Cisco 2500 Series Router

Wed, 2012-07-11 07:00
Command Line

If you have built a home lab (or are running really ancient hardware in production), you may find yourself in need of resetting the password configured on a 2500 series router. Depending on the router platform, the syntax is different. Here's how to do it on a 2500:

1. Reboot the router and send a break sequence to enter ROMMON mode. Break sequences can be sent using a Ctrl+Break key combination, or if you are on a system that doesn't have a break sequence, try using your terminal software to send a break sequence.

2. (optional) Type the letter O and hit enter. Record the existing setting, it's most likely 0x2102.

3. To reset the configuration register and have the router bypass the startup-config, type the following:

o/r 0x2142

To boot the router, type the letter i and hit enter.

Cisco Live 365

Wed, 2012-05-02 07:27

Cisco has created a new rendition of their Cisco Live website called Cisco Live 365. You can register with the site for free and gain access to some of the conference materials presented at the various Cisco Live conferences around the world throughout the year.

If you are signed up for CiscoLive2012.com (because you are attending Cisco Live in San Diego this June), then your credentials for that website don't apparently work automatically at the new site. To get access to the new site using your current credentials, login to the old site CiscoLive2012.com, then click on Registration, and click on the huge button that says Enter Cisco Live 365. A new tab or window should open and voilà, you're in.

Upgrading 3750X can take longer than you think

Sat, 2012-04-07 19:51

I recently upgraded a Cisco 3750X stack to a newer version of IOS. Since the production system I was planning to upgrade had some critical systems on it, I tested the process on a stack in the lab first.

At the outset I figured "no problem, this will take a few minutes to reboot and we'll be back up and running." Little did I know I was in for a long wait... Unbeknownst to me the version of code I was upgrading to included a Microcode update which adds a considerable amount of time to the process... emphasis on considerable.

The stack was running 12.2-53.SE2 and I was upgrading it to 12.2-58.SE2, which at the time of the upgrade was the recommended 12 version (I've had problems with IOS 15 on this platform, so I'll be sticking with version 12 for now).

Networking 101 Video - Switch Latency

Thu, 2012-04-05 07:11

Jimmy Ray Purser from TechWise TV  provides a pretty good review of how switch performance is measured. Topics reviewed include cut-through switch latency, store and forward switch latency, FIFO, LIFO, and LILO. Check it out if you've always wanted to know how to measure the speed of a switch.

Here's a direct link if the video embed code doesn't load in your browser: http://youtu.be/C8cTrhcbOLc

CCNA Service Provider

Thu, 2012-03-15 20:46

I received an email announcement today regarding Cisco's new CCNA Service Provider certification. This is in addition to the already available CCNA Service Provider Ops certification.

There are two exams that need to be passed in order to achieve this certification, the SPNGN1 and SPNGN2.There are no prerequisites.

You can check out the full list of exam topics on each exam page, but needless to say the list is extensive. By the end of the certification, you should have a good introductory understanding of the following:

Cisco Security Advisory - NX-OS Denial of Service Vulnerability

Sat, 2012-03-10 09:36

Cisco recently announced a vulnerability in their NX-OS for the 1000v, 5000, and 7000 platforms. If you are running Nexus in your network, be sure to check this one out because it could cause an outage.

In order for this vulnerability to be exploited (or randomly occur), a malformed IP packet has to enter into the Nexus and one of several conditions can trigger the problem. The advisory notes provide a few examples of how to trigger the problem including the following: a malformed packet with a TTL value of 1 that would cause the Nexus to send an ICMP time exceeded error message. The process of generating the ICMP message could trigger the bug.

What's Vulnerable and How do I fix it?

Here's a list of the versions with the vulnerability and the version with the fix, per platform:

Navigating the IOS command line

Mon, 2012-02-20 09:23

I decided to put together a quick blog post on some handy IOS file management commands. I'll likely add to this again in the future to make it more complete, but I wanted to get something started, so here it is..

dir - Get a directory listing of whatever path your are in. 

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Dr. Radut