Hyper-Awareness – Ciscocmd for monitoring bandwidth on ALL of your interswitch links at a glance

CLICK HERE FOR MORE DETAILS on how to utilize Ciscocmd and Syslog to monitor you entire network at a glance and keep your finger on the pulse of your global communications infrastructure.

Hyper-Awareness – Ciscocmd for monitoring Bandwidth on ALL of your interswitch links at a glance.

Using ciscocmd, this article will expose the power of a properly selected variable sorted and displayed in a text file. In short, you will become hyper aware of bandwidth hotspots across your entire global enterprise infrastructure. With ciscocmd will know at a glance that an uplink of a particular access switch is hitting it’s bandwidth capacity limits, even if you have ten thousand interswitch links in your network.

The tools we are going to use to achieve this Zen state of hyper awareness are:

• Ciscocmd
• Cisco Discovery Protocol
• Output Queue Drops
• Unix utilities

Before a explain the few lines of code, I will begin with an overall explanation of what the script will do. By doing this hopefully, you will understand the steps, I am taking with the code, as well as give you an idea of how easy it is to script with ciscocmd.

The goal of this script is to quickly inform you of any interswitch link that is exceeding it’s maximum bandwidth. So then there are a few questions.

• How do we find interswitch links?
• How do we detect if the switch has exceeded it’s maximum bandwidth?
• How do we present this huge amount of information without completely overwhelming you?

How do we find interswitch links?
We gather information about all interswitch links from the prespective of a particular switch, with Cisco Discovery Protocol. The reason you are primarily concerned about interswitch links and not all links is because as a network administrator you are usually concerned more with interconnectivity bottle necks as opposed to user hosts. However, if you really wanted to, you could modify this script to show you every single port on your network (probably not useful or a good idea).

How do we detect if the switch has exceeded it’s maximum bandwidth?
Once we find all interswitch links from the prespective of a particular switch, we check to see if there have been any output Queue drops. An output queue drop indicates that an interface has been forced to drop a packet while the packet is trying to exit or egress the switch or router. The packet is dropped because the queue is full, in other words the interface has reached it’s capacity to transmit packets. You may be thinking, “What about incoming packets”. The way you catch incomming or ingress packets is to monitor the output queue of the directly connected switch.

How do we present this huge amount of information without completely overwhelming you?
The way we present this large amount of data in a simple actionable manner is using a sorted list. We will sort the list so the highest interface output queue drops will be presented at the top of this list. Even if you have thousands of interswitch links, you can get an accurate read on the overall bandwidth capacity of your network by quickly glancing at the top of the list.

Example of output:
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switch1 GigabitEthernet1/14 Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 88
switch1 GigabitEthernet8/4 Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 5
switch1 GigabitEthernet7/8 Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 0
switch2 GigabitEthernet7/7 Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 0
switch2 GigabitEthernet7/5 Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 0
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CLICK HERE FOR MORE DETAILS on how to utilize Ciscocmd and Syslog to monitor you entire network at a glance and keep your finger on the pulse of your global communications infrastructure.

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