Scrutinizer can present network traffic data in a number of different ways, including showing the amount and type of traffic that is flowing through an autonomous system (or AS).

An autonomous system is a collection of connected Internet Protocol routing prefixes under the control of one or more network operators, and presents a common, clearly defined routing policy to the Internet.


Does your organization need an autonomous system number (ASN)?  Maybe…

If you have a multi-homed network to different providers and have routing policies to different external peers, you may want to consider what’s involved. Read the RFC 1930 – Guidelines for creation, selection, and registration of an Autonomous System (AS) .

Most companies don’t need their own ASN because the ISP’s ASN is adequate.

Whether you need your own ASN or use the ISP’s, Scrutinizer’s ability to monitor ASes allows network administrators to see how much traffic is traveling between registered ASes.

The router must be configured to include AS information in order to display AS statistics in Scrutinizer.

Check out Cisco’s Whitepaper on BGP configuration for help on BGP configuration. Please be careful with BGP configuration changes as these configurations can have a significant impact on the router’s resources.

Once BGP is properly configured on the router, you can enable the export of the AS information within the NetFlow packet by applying the command below:

ip flow-export {version}[peer-as | origin-as]

I’ll explain the differences between the two AS options:

peer-as” will give you the as-numbers for the networks you have direct BGP peering with. For instance, if you peer with AS1 and reach all others through that, “peer-as” will report all traffic as AS1.

origin-as” produces as-numbers for the end AS the traffic is coming from, rather than your neighbor’s or the transit ASes along the way. For example, if is in AS666, and you reach it through your peer AS1 (from the example above), AS666 will be reported in the flows.

Now you should be able to see traffic grouped by AS.

Scrutinizer v7 increases this functionality by not only showing you AS from either source or destination, but also AS-to-AS, which shows the source AS Traffic to destination AS.

I’m really looking forward to Scrutinizer’s new release.


Steve Cunha author pic


Stephen joined Plixer in 2011. Steve’s efforts over the years have helped many customer gain better Visibility and Network Analytics. With more than 5 years of successful technology consultation, Steve has become a thought leader, focusing on how Scrutinizer can be part of a system incorporating other solutions such as Gigamon, Statseeker, Uptime, InfoBlox and Splunk. Firm believer that most organizations will have a larger SDN implementation and greater leveraging the Cloud in the next few years. Steve resides in Scarborough, ME with his wife and two sons.


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