What is the CHIX? | Why non-ISP's should peer | Who uses the CHIX? | How does it work? | Getting Started | Route registry | Show CHIX Routes | Change CHIX Route filters | IPv4 Looking Glass | NZ Internet Exchanges | Home

How does it work?

There are two route servers which hold details of the routes exchanged at the CHIX. These servers filter routes in two ways:

  1. Incoming announcements are checked against individual filter lists for each peer.
  2. Outgoing announcements are filtered to make sure that routes are not announced for RFC1918 addresses and other bogon or martian addresses.

The filter lists and other details of the route server configuration are built automatically from an RPSL database using the RtConfig tool from the IRRToolset. If you need to change the prefixes you want to announce you can use the Change CHIX Route filters tool.

More information on using RPSL is available from the APNIC page About the APNIC Routing Registry. For a number of reasons we run our own Routing Registry Database at present. The CHIX Routing Registry data is available either by using a standard whois client connected to:

  • whois.nzix.net:43

or using a web based interface:

You can examine the CHIX routing policy by looking up the details for AS24388

A list of the Autonomous Systems connected to the route servers are given in the RPSL as-set objects AS24388:AS-PRIVATE and AS24388:AS-PUBLIC. The AS numbers in the private list have been assigned by CityLink for use on the CHIX only. The AS numbers in the public list have been assigned by one of the Regional Internet Registries such as APNIC.

Each AS has a list of networks they announce to the route servers given in an RPSL route-set object. For example, the numbers that CityLink announce to the CHIX are given by AS24388:RS-ROUTES:AS23754 and incoming announcements are checked against filters constructed from these lists. If you are a CHIX peer, you can check the list of networks that you are allowed to announce to the CHIX by looking up the relevant route-set AS24388:RS-ROUTES:AS<YOUR_AS>. Please get in touch with us with any corrections.

The list of exported routes is checked against an RPSL filter-set called fltr-bogons which is constructed from two other filter-sets fltr-martian and fltr-unallocated Thanks to Rob Thomas at Team Cymru for these filters.