AS8405 SONTHEIMER-IT

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.