AS13904: the COSLINK network

AS13904 is an internet Autonomous System operated by COSLINK (the United States). Here is what that means and why this number may show up when you investigate a connection on your network.

What is AS13904?

An Autonomous System (ASN) is a block of networks under a single control with its own routing policy on the internet. The number AS13904 was assigned to COSLINK by an RIR (regional internet registry). All traffic entering or leaving that network is announced under this number.

Reach on the internet

AS13904 currently announces 30 IPv4 block(s), totaling about 35.1 thousand addresses (35,072 in all), registered in the United States. Services from COSLINK are reached through these addresses.

What it means to see AS13904 on your network

When you investigate where a connection from your computer or phone comes from (or goes to), you may find AS13904. That means the other end sits on the COSLINK network (the United States). It can be legitimate — a cloud service, an ISP, a CDN — or an unexpected connection worth checking.

How to see every connection and network your devices reach

Tracing one connection's ASN at a time is tedious. Sentinela, by PC Monitor, maps the devices on your network, shows what is exposed to the internet and helps flag suspicious connections and devices — running on your Windows. Meet Sentinela.