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RouteExplorer™ Tutorial -- Visualization

Compare the network-wide routing table between any two points in time

If you are a network engineer responsible for an enterpriseor service provider network, you have formed a mental picture of what youperceive to be the stable state of your network – let’s call it a “baseline”.But when something goes wrong, how do you pinpoint exactly how and where yournetwork is “out-of-sync” with your baseline? How do you accurately determine the baseline in the firstplace? And if your organization hasmultiple engineers with different domain responsibilities and/or shifts, how doyou arrive at a common picture of a baseline? Route Explorer’s History Navigator and “RIB Before-and-AfterComparison” can be a great help.

Route Explorer’s History Navigator shows you a histogram ofa number of vital network statistics – including events, number of routers,routing adjacencies and prefixes. Figure1shows an example.

Figure 1

The lower timeline identifies a period of several days whenthere were no changes to the number of prefixes advertised in the network. This period was followed by severalhours of network churn. The stableperiod can act as a baseline to analyze the instability. Route Explorer can do aBefore-and-After Comparison to show you what has changed between two points intime. By selecting a stable timeas the “before” time, you can pinpoint the potentially affected links androutes. Figure2illustrates such a comparison for the BGP RIB.

Figure 2

Note that in this case there is a period of extremely highBGP churn at the left of center of the events timeline. Route Explorer allows you to select atime before the churn began and after (the blue vertical lines) for the RIBcomparison. The results of theanalysis are presented in a tabular or bar graph form. In this case, the analysis shows thatdespite the high churn, the number of routes that have been lost is less than1% from each of six BGP next hop routers of this network. To investigate further you may want toget a summary of the events from Route Explorer for the time period of thechurn. We show how in the nextsection.

HOW TO:

1. Open the “DemoJitterISPOct01” topology

2. Open history navigator: click Tools->History Navigator

3. Display the Networks timeline: Click on “Graphs” button inHistory Navigator

a. Select the “Networks” button.

b. Resize the History Navigator if necessary to display both theevents and networks timelines.

4. Zoom the timelines around the center one-third of the timeperiod. Note the period of stabilityin Networks and the churn in the events following.

5. Next, open the “DemoTier1ISPJun02” topology

6. Open the History Navigator.

7. Compare RIB at two points in time, one before the series ofspikes at the center of the time line and another after:

a. Click on “Analysis” drop down and select “RIB Before-and-AfterComparison”

b. Select start time at the left of the spikes and end time atthe right of them, using blue crosshairs cursor.

8. Resulting tables can be sorted, filtered and viewed as bargraphs (see above)

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