AS11985 ASN-SSA

ASN-SSA is a network of the US Social Security Administration, the federal

agency that runs retirement, disability and survivors' benefits. Every announced

prefix is registered to the SSA, and the sampled reverse DNS resolves under

ssa.gov, so the agency-sounding handle is confirmed by both the registry and

the network itself.

What it's used for

• Federal government service delivery. The AS originates about 18,700 IPv4 addresses, built on 137.200.0.0/18 and its more-specifics plus 199.173.224.0/21, together with six IPv6 prefixes out of 2001:1930::/32 — a properly dual-stacked agency network, which is a US federal mandate rather than an accident.
• The space carries the SSA's own internet-facing infrastructure. The one PTR observed, s01dace.ssa.gov, is a first-party name in the agency's own domain.

Notable

• Three observed neighbours against a five-figure address count is the expected federal enterprise shape: a large, stable allocation reached through a small set of upstreams (in practice government network service contracts), with no peering business of its own.
• Both the covering /18 and a stack of nested /19s and /20s are announced. That is deliberate traffic engineering across redundant circuits, not evidence of separate operators inside the block.

Interesting

• IPv6 is not decorative here — six prefixes from a /32 implies a real internal addressing plan, which puts the SSA ahead of most enterprises of comparable size.