Internet Exchange Point(IXP) questions

Michael K. Smith - Adhost mksmith at
Fri Feb 18 12:39:24 CST 2011

From: Yaoqing(Joey) Liu [mailto:joey.liuyq at]
Sent: Thursday, February 17, 2011 7:04 PM
To: Michael K. Smith - Adhost
Cc: nanog at
Subject: Re: Internet Exchange Point(IXP) questions

On Thu, Feb 17, 2011 at 8:17 PM, Michael K. Smith - Adhost <mksmith at<mailto:mksmith at>> wrote:
> -----Original Message-----
> From: Yaoqing(Joey) Liu [mailto:joey.liuyq at<mailto:joey.liuyq at>]
> Sent: Thursday, February 17, 2011 6:03 PM
> To: nanog at<mailto:nanog at>
> Subject: Internet Exchange Point(IXP) questions
> I'm doing some research on multiple origin AS problems of IXPs. As I know,
> generally there are two types of IXPs
> type 1: use exchange routers, which works in layer 3
> type 2: use switches and Ethernet topology, which works in layer 2.
> So I have a couple of qustions:
> 1. For type 1, the exchange routers may use several IP prefixes for routing,
> how often does the IP prefixes have their own AS?
> 2. For type 2, all peers connected to the IXP must work in the same subnet
> required by Ethernet rules. Is possible that the subnet IP prefixes belong
> to some private IP address space, such as 192.168.x.x? How often does this
> happen? If the subnet only contains public IP addresses, how are the
> addresses announced?
> Thanks,
> Yaoqing

On the Seattle Internet Exchange (SIX) we have ARIN-assigned addresses that we use on the Layer 2 fabric (your type 2 above).  Hopefully the addresses aren't being announced at all, although we sometimes have to chase down people that announce it.  Those addresses aren't the destination for any traffic, they are merely part of the transport to a destination, so there is no need for them to be in the DFZ.

But I just checked the IXP prefix list, and found SIX owns prefix<>. And it has been announced by three ASNs, AS11537(Internet 2), AS3130(RGnet, LLC) and AS25973(Mzima Networks, Inc). I'm not sure if my info is correct. Does SIX own its own ASN other than the three above?


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