Tag: Cisco

Cisco RRM Restart

Recently when working with Cisco wireless networks I have been really working to get Dynamic Channel Assignment tuned in and really understand much more about it. Some of the important things to make sure you are setting correctly include Anchor Time, DCA Interval (please don’t use the default, there is a blog post coming about that), etc.

One thing that became an option via CLI in the 7.3 code train was the ability to restart the RRM DCA process on the RF Group Leader. Why is this important I can hear some of you saying, or why would I want to do this? Here are a couple of examples of why.

If a controller enters or leaves an RF Group or if the RF Leader leaves and comes back online, as in a reboot, DCA will automatically enter startup mode to reconfigure DCA regardless fo the settings that have been changed on the controller, i.e. not using default of 10 minute intervals. But is there a need to do this manually? Yes.

As you add new APs into the network it is a good idea, and a Cisco recommendation, to initialize DCA startup mode. The reasoning behind this is as APs are added, DCA needs to rerun calculations and provide a more optimized channel plan based on the newly added APs and what the other APs are seeing over the air. When this command is run, it should be done from the RF Leader and will only affect the RF Leader.

The command should be run on both 2.4 GHz and 5 GHz radios:

2.4 GHz: config 802.11b channel global restart

5 GHz: config 802.11a Chanel global restart

Cisco Prime, What is it good for?

By now the majority of us have used some itinerant of Prime, NCS, or WCS for wireless management, placing APs on maps, template building, backups, etc. But what else can Prime really do?

I recently did a project where we needed to integrate a new prime instance with the standard CMX installs, which is a chore in and of itself (a post on that is coming), wireless management for the various buildings they have and some jobs to do back-ups of switch, router and ASA configs. There then a larger project to push QoS to a large number of switches, around 1,000 or so. APIC-EM was attempted but there was such a variety of switch models, chassis, IOS versions, QoS abilities to name a few. With these variances, only about half the switches were supported in APIC-EM. Since we had just stood up the new Prime, it was decided to use Prime to push these configs to the switches. Let’s be totally honest before we begin, Prime was not built as a wired network management suite. It was built form the old WCS and then pieces were added and we now have this. It is not horrible, but it is not the best for wired either.

Fun now ensues.

Initial thoughts were to just push Auto-QOS to all switches, however there was a requirement for more granularity. More fun begins. I start to set out writing config scripts in Prime for a couple of switch models to test on, 4506-E and 4500X. Should be simple right, take a QoS config, put it in the template, select the switch and go. To write a script in Prime you need some knowledge of Apache scripting commands which can be a little confusing in itself if you not done coding previously, like myself. I was lucky and had someone who could do these scripts and teach along the way.

Some of the pitfalls we had along the way included the need to build-in smarts to see what platform the switches were to use the proper commands, what version of code was on the switch, querying the switch to gather port types and line cards installed. To accomplish this you have to first begin with understanding the Prime database structure and how to call the appropriate variables for what you need. This excerpt from the Prime 3.1 user guide is a good place to start to understand the variable and how to call them from inside the CLI config templates. Also, see this Support Community Post which has some good info as well.

Now we have gotten our background info we are ready to start jumping in and breaking, I mean writing, some scripts. This was a lot of trial and error for me as we had to touch at least one version of each type of switch and verify we had the right CLI commands to enable QoS as it differs on platforms and even code trains within the same platforms.

After a couple of false starts with getting platforms commands, interface commands and settings just right we were able to get a working script for the first group of switches, the 4506-E,4500-X and a test Nexus 7K. The script ended up looking like this:

$Platform.contains(“Data Center Switches”))

The trick is we had to have the platform command and specifically the “Data Center Switches”. If a sh platform is run on the switches this is what is returned as the platform name. The reason we were looking at this command was it was easier and seemed more stable to call the platform type than the $Version.contains command to check IOS vs. IOS-X.

policy-map configs for IOS-X

#else

This is where we specify non-IOS-X config elements

access-list

policy-map

class-map

#foreach ($interfaceName in $InterfaceNameList)

#if ($interfaceName == (“GigabitEthernet0/0”))

#else

int $interfaceName

service-policy output QOS-SHAPE

service-policy input QOS-MARK

#end

#end

#end

These are the lines where the magic really happens. This code is going to the Prime DB and doing a querying for interfaces using the $InterfaceNameList and then we are checking if $InterfaceName == (“GigabitEthernet0/0”)) which is generally the management port on the switch. Of the port has that name we do not apply any Qos to it. If not any other $InterfaceName we apply the service-policy config to.

Gotcha 1 for me, make sure you account for all the #end statements you need. It becomes easy to lose track and it will frustrate you when you import to Prime and try to test it the first time.

With this basic config, you can now customize based on switch type.

The next step to deploy is we have to get this config into Prime, if you didn’t write it there, and make sure all our variables are working properly. After importing into Prime the Form View tab and Add Variable tabs will now be populated.

Our next post will cover Deployment of the newly created script to either 1 or 1,000 switches depending on the need.

 

 

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