Fun with Procurve switches

What would you do if you have a bunch of Procurve switches and some free time?

Well, as I found out, you can have a little fun besides just learning and working.



This video was found through this blog: http://bhbodeezy.com/tag/locatorleds/

Earlier this week, I released a suite of Windows network troubleshooting utilities called Pinkie through a website named ipUptime.net.

Everything went well. The public seems to welcome it and as I monitor the statistics for the site as well as the download counts from other download sites, I realized that something is wrong with my site statistics; the numbers don't match up and my number came up short.

As I found out, if people download the Pinkie through the link on my site then the download count is incremented. But if they had download it from other sites, using the URL I had published then the download is not accounted for.

Changing the published URL for all other sites will be time consuming so I was looking for a better solution to the issue. Then I remember ASP.net 2.0 supports URL Mappings. So by using URL Mappings, within a minute or two, my problem is solved.

Here's the syntax for URL Mappings:

<urlmappings>
<add url="~/newurl.aspx" mappedurl="~/oldURL.aspx"></add>
</urlmappings>

Best use for URL Mappings are for shortening long, hard to remember URL to something short & easy to remember or in my case, correct a mistake and save time.

Simple Website

A friend of mine runs a small business in Houston, TX and needed to enhance the company's web image.

With the little free time I had, I was able to put together a simple, mostly static HTML site for her.

You can check it out here: eyecareforyouonline.com.

Blogging again!!!

It's been a long while since I posted a blog. Well, apparently, I had forgotten my password and was unable to recover it since the email account I registered with Google wasn't active. Therefore, I wasn't able to login to the site.

In a recent Networking project called Pinkie, I needed to activate the web hosting account again and finally able to reset the password to the blogger account.

So in the comming days, I'll start blogging again when I get some free time.

Virtual Private Networks Troubleshooting - Part I

I've seen quite a number of posts asking why VPN users are not able to access their network even though they have been successfully connected.

Let's try to troubleshoot what happens here. A very common VPN setup is to use 2 NICs and run Routing and Remote Access on one of them. The benefits of this would be that you can isolate VPN traffic and keeping it from overloading the NIC that handles the internal network traffic. One thing to note for is that the two NICs have to be assigned IPs from different networks or subnets. For example:

1st NIC (VPN): 192.168.1.2 /24
2nd NIC(internal network): 192.168.2.2 /24

(Don't worry if you don't understand the /24. It's called the slash notation for the subnet mask which is the equivalent of 255.255.255.0)

Through the initial RRAS setup, users will be able to connect to the VPN just fine and will be assigned an IP address of one of the networks. The problem arise when they try to connect to network resources on through the 2nd NIC (the other network). This is due to the fact that Windows doesn't know how to route the packets from the 192.168.1.0 network to 192.168.2.0 network.

You can tell Windows how to route traffic between the two NICs by configuring a static route with the "Route" command. Type "Route /?" at the Command Prompt for more information.

And as usual, I have a second way to accomplish the job by turning on Routing using RIP or OSPF and add the two NICs to it.

One thing that I see lacking from most Windows Administrators is the understanding of TCP/IP and network routing. I would recommend Windows Administrators to take CCNA anytime. Even though it might seem so remote from their daily tasks, one can walk away from a CCNA class with so much helpful information that makes their job much easier to do.

Switch Port Security

If you are working in a strict security environment then switch port security is a must. Configuring switch port security could become a tidious task. However, if you can control the environment when you setup the network, this little trick can help you save a lot of work.

Instead of configuring port security and manually enter MAC address for the port, you could plug all your hosts in then issue the following commands:

Switch(config)#int range f0/1-xx
Switch(config-if-range)#switchport port-security
Switch(config-if-range)#switchport port-security maximum 1
Switch(config-if)#switchport port-security violation restrict
Switch(config-if-range)#switchport port-security mac-address sticky
Switch(config-if-range)#end

The first command takes you to the interface range configuration mode; the next two turn on the port security and set a maximum number of mac addresses to 1. "Violation restrict" will not allow traffic for any host whose mac address is different than what the switch has learned for the port in question. After that, the "mac-address sticky" commands instruct the switch to learn the mac address dynamically and remembers it for the each port.

Basic Load Balancing

Load Balancing normally has two modes of operation: Per-Destination and Per-Packet.

Per destination load balancing means the router distributes the data packets based on the destination address. If you have two paths going to Host A & B on the same network then all packets for Host A will travel over the first path and all packets for Host B will travel over the second path. This will preserve the packet order which is very useful in certain applications; however, it could result in unequal usage of the network links as bandwidth & load are not taken into route calculation.

Per packet load balancing means the router sends one packet over the first path and second packet over the second path; all going to the same destination. Per packet load balancing guarantees equal load across all the links; however, the packets may arrive at the destination out of order because of different delay/bandwidth may exist on different paths.

Per destination load balancing is enable by the command:

Router# config t
Router(config)# interface Ethernet 0
Router(config-if)# no ip route-cache

Now the router CPU will look at every single packet and spread them across the different path available in the routing table for the destination. This is not recommended on low end server as it could crash the router because the CPU must do all the processing and might not be able to handle it. To enable fast switching, use the following commands:

Router# config t
Router(config)# interface Ethernet 0
Router(config-if)# ip route-cache

Newer switching schemes such as Cisco Express Forwarding (CEF) allow you to do per packet and per destination load balancing more quickly but it does imply that extra resources will be needed to maintain it.

Reload

Working remotely with routers & switches you don't have the flexibility to reset the devices at will when things go wrong unless you can control power distribution to the devices.

This is where the Reload command comes in handy. Before making changes to the configuration, you can enter:

Reload in 10

which will reload the device in 10 minutes. Once the command is entered, you can proceed with the configuration changes. If things go wrong and you lost connectivity to the device, try back in about 10 minutes since the device will get reloaded with the original startup-configuration and restore connectivity.

Once you confirm that your new configuration is working properly, you can issue the command:

Reload cancel

to cancel the reload. I find this trick to be very useful when I have to telnet or SSH to a remote device and hopefully you too.