AS8676 PRTSYSTEMS PRT Systems Ltd Clearhost Transit AS

PRTSYSTEMS is PRT Systems Limited, a small UK operator based in West Sussex. The AS is the transit backbone for the company's Clearhost umbrella, under which it runs several separately branded ISP and hosting services.

What it's used for

AS8676 exists to carry the other brands rather than to serve customers directly. PRT Systems runs a family of retail identities — PRT Systems itself, Dico, UMIS.net, Neo-Tel, SystemIP and My Hosting Bubble — several of which hold their own AS numbers, with AS8676 sitting upstream of them.

The evidence matches that description:

• Reverse DNS on the sampled addresses is pure backbone: core1.thd.dico.net.uk and core2.thw.as8676.net. These are core routers, named by site code, one of them under a sibling brand's domain — exactly what you expect when one AS backhauls several.
• 38 observed BGP neighbours against only ~8,700 IPv4 addresses. That ratio (many adjacencies, little address space of its own) is the transit signature: the value of the AS is in the peering, not the inventory.
• The inventory itself is a scatter of small RIPE blocks — 194.11.244.0/23, 194.13.108.0/23, 194.13.140.0/23, 194.13.236.0/23, 185.109.136.0/23, 31.7.8.0/21, 217.65.160.0/20 — self-registered and consistent with an operator that has accumulated allocations across its brands.

Notable

The 217.65.160.0/20 prefix has been in the routing table since 2002, so this is a long-established small British network rather than a recently reissued number. It also announces IPv6.

Interesting

The multi-brand structure is why a name-only reading of this AS misfires: the holder, the rDNS domain and the retail brand a customer actually buys from are three different names, and none of them is "Clearhost".