Sofia · Bulgaria

Sofia's exchange traffic concentrates in two near-equal points, NetIX with 133 participants and BIX.BG with 128, followed by B-IX at 55 and TurkIX Sofia at 32. The four smallest exchanges add 48 participants between them. Colocation carries comparable weight, with 436 network presences across 14 facilities against 396 exchange peers, and TELEPOINT Sofia Centre alone lists 184 networks ahead of Equinix SO1 at 58. BIX.BG records six Bulgarian carrier ASNs and B-IX four, though the entries for A1 Bulgaria, Vivacom and Yettel Bulgaria carry no mobile ASNs to match against them.

An address that geolocates to Sofia often reaches a device somewhere else in Bulgaria. Operators announce address blocks from a registry record that names one administrative address, and a national mobile network can route subscribers from anywhere in the country through a handful of gateways in the capital. Geolocation databases read the operator's own published location for the prefix, so a block registered to an address in Sofia resolves to Sofia whether the handset using it sits there or in Varna.

Checking the origin ASN on the specific prefix tells you more than a city label. A route that starts in one of the Bulgarian carrier ASNs peering at BIX.BG or B-IX behaves differently from one originating in a network that only appears in TELEPOINT Sofia Centre or Equinix SO1. The netname and the registered holder on the prefix show which organisation holds it, and the exchanges a network joins in Sofia say where its traffic enters and leaves the local internet.