AS8405 — SONTHEIMER-IT

AS8405 announces 9 IPv4 prefixes covering 10,496 addresses and 0 IPv6 prefixes.

About this network

SONTHEIMER-IT, registered to PE Sontheimer Bernd, is the autonomous system of sdt.net AG of Aalen, Baden-Württemberg. The company began life in 1987 as Sontheimer Datentechnik GmbH and was among the first German ISPs to sell nationwide internet access in the mid-1990s; it became sdt.net AG in 2006 and now trades as a brand of TNG Stadtnetz AG.

What it's used for

• Regional fixed-line access in Baden-Württemberg: VDSL and fibre internet, plus telephony, for homes and businesses. Several assignments inside the space are explicitly named VoIP-Pool, matching the telephony side of the product line.
• The AS is single-homed behind TNG Stadtnetz, which is also the parent brand.

Notable

• The address inventory is not all sdt.net's own customers, and should not be geolocated as one block. Part of 217.140.64.0/19 is sub-allocated under an IPXO netname (the IP-leasing marketplace), and a /23 inside it is assigned to Arm in San Jose, California. So some prefixes here front third parties on another continent.
• Reverse DNS is essentially absent across the announced space, which removes the usual signal for separating subscriber pools from leased or business blocks.
• The registry name is a person, not the trading name — reading the holder field alone gives no hint that this is a long-running German ISP.

Interesting

• The SWA and SDT contact handles scattered through the objects are the fossil record of the Sontheimer lineage, still visible decades after the company changed its name twice.

This description is AI-generated, best-effort context — not authoritative, and provided without any guarantee of accuracy.

Announced prefixes

• 5.252.124.0/22
• 45.87.16.0/22
• 185.218.168.0/22
• 193.35.216.0/24
• 193.36.3.0/24
• 193.36.42.0/24
• 193.188.154.0/23
• 217.140.72.0/21
• 217.140.80.0/20

Upstream networks

• AS6735 TNG Stadtnetz GmbH

Adjacent networks

• AS6735 TNG Stadtnetz GmbH