In the last post on IP SLA, we introduced the service to you. In this post, we will take a close look at the various operations that are available and provide some guidance on what they gather statistics for, and how we might use the operations in an actual network (or of course the CCIE practical lab).

Keep in mind that how we run operations to gather information about the performance of your network is very flexible. You can run tests in an on-demand fashion, literally kicking the test off when you want and stopping it when you want. Or you can take advantage of a robust scheduling engine, that even includes randomization of your network tests. In a future blog post on IP SLA, I will be sure to detail for you all of the wonders of scheduling. In fact, we will even detail the various settings for statistical storage and threshold alerting.

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This blog entry is compliments of a recent forum post. The author had an excellent question. Sure a Cisco IOS-based router can utilize address auto-configuration and seamlessly dole out addresses to things like PCs on the segment, but how in the world are those PCs going to get the necessary IP extras like DNS domain information? Well, it turns out that the rumor about the complete and total demise of DHCP in an IPv6 world is completely false.

In fact, Steve Deering (a key figure in the development of IPv6) has often joked about how (ironically enough), DHCP for IPv6 has undergone more transformations than any other part of the standards. It is like a host out there with a real short lease duration.

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The CCIE R&S Lab Exam starts with a real bang – the Troubleshooting section. Cisco promises us that we will see about 10 to 11 Trouble Tickets against a larger than normal (for the lab) topology. This topology consists of about 22 routers and switches. These devices are emulated Cisco hardware running in Cisco’s own version of a Dynamips-like product called IOU (the IOS on Unix).

OK, so we read these rules and we immediately think: “No problem! Bring it on! What is the big deal!?!?” Well, the big deal is two fold. One is the fact that you are only given a total of 120 minutes for solving the Trouble Tickets, and two is the fact that the potential scope of the Trouble Tickets is the entire R&S blueprint.
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I’ve received a few emails regarding my previous posts, plus some questions during the CCIE Wireless bootcamp last week.  Namely, the questions/statements were the following:

1. Your statement about the 802.1p value only applying to the WLC itself and not to the AP wired correction is incorrect
2. You did not include anything about WMM Disabled, so the conclusions could be incorrect for that scenario

Let me address each one separately, starting with the 802.1p value.  First, the value does indeed affect the wired traffic passing through the WLC.  So, if a frame is received with CoS 5, but the max 802.1p value is 3, the frame will be remarked to CoS 3 when the WLC puts it on the wire.  Also, if the 802.1p type is None, then the frame will be remarked to CoS 0.

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In this blog post we will examine important overview information regarding the IP SLA service found on Cisco network devices. Future blog posts will focus on more detailed aspects of this important networking service.

The IP SLA has had many names throughout its existence. When I first encountered it in Cisco networking, it was with very early versions of CiscoWorks and it was named the Response Time Responder (RTR). That name must have been so terrible that some texts referred to it as the Real Time Responder (RTR). At some point, Cisco renamed the utility the Service Assurance Agent (SAA) but that name did not stick for long either. Today, even though we see traces of the old names in the IOS and in Cisco networking texts, Cisco wants us to know this service as the IP SLA (Service Level Agreement) component. This tool is truly excellent for built-in network testing. In fact, it is a key ingredient for sophisticated implementations of Performance Routing (PfR).

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