Network Tools Archives - Justin Wilson (j2sw)

The Third App from J2sw: Prefix Advertisement Checker

July 31, 2026 by j2sw

A prefix can appear in the global BGP table and still have a routing problem. The route may originate from the wrong ASN. Its ROA may also authorize a shorter prefix but reject the advertised prefix length. Checking each part normally means pulling data from several routing tools. The J2SW Prefix Advertisement Checker, my 3rd … Read more

Introducing the J2sw MTU and Encapsulation Calculator

July 28, 2026July 28, 2026 by j2sw

Ever wondered what the effects of different combinations of PPPoE, GRE, and others have on the MTU of a packet? I am excited to announce the first of many J2 Network tools: the J2SW MTU and Encapsulation Calculator. You select the service MTU and the encapsulation used on the path. The calculator then works out … Read more