AS9426 WESTPAC-AS-AP Westpac Bank

AS9426 (WESTPAC-AS-AP) is held by Westpac Banking Corporation, one of Australia's four major banks. This is a corporate enterprise AS: the bank running its own routed address space for its branches, corporate sites and internet-facing services, not a network sold to anyone else.

What it's used for

The evidence is a large-enterprise pattern, and the neighbour count is what gives it away. The AS originates 55 IPv4 prefixes totalling 20,992 addresses but is observed with only 3 BGP neighbours. A carrier with 55 routes would be peered with dozens or hundreds of networks; a bank multihomed to two or three Australian transit providers for resilience would look exactly like this. The address inventory is dominated by 166.120.0.0/16, a legacy block registered to Westpac Banking Corporation, sliced up into a long tail of /19s, /20s, /22s and /24s — the deaggregation you get when an enterprise pins individual site or service ranges to particular upstreams. Alongside it sit smaller APNIC-region blocks (203.24.0.0/22, 203.24.4.0/22, 203.23.44.0/24) and 110.5.80.0/20 and its more specifics. No IPv6 prefixes appear in the RIS view.

Notable

• The core block 166.120.0.0/16 is registered to Westpac Banking Corporation and dates back to the early 1990s, an era when a large corporate could still obtain a /16 directly.
• 55 prefixes against only 3 neighbours is a strong enterprise signature: heavy internal deaggregation, almost no external peering.
• The AS carries no IPv6 in the observed routing table.