On Thu, Oct 22, 2009 at 10:18:48PM +1100, Karl Auer wrote:
On Thu, 2009-10-22 at 11:08 +0000, bmanning@vacation.karoshi.com wrote:
On Thu, Oct 22, 2009 at 09:44:38PM +1100, Karl Auer wrote:
On Thu, 2009-10-22 at 10:30 +0000, bmanning@vacation.karoshi.com wrote:
The RA contains a preference level... maybe that doesn't cut it if
I point you to a fairly common Internet architecture artifact, the exchange point... dozens of routers sharing a common media for peering exchange.
And how do they discriminate now, with IPv4?
IPv4 has no concept of RA/ND. to make this construct work at all in IPv6, all participants have to turn -off- RA/ND to prevent one or more routers trying to impose their views of addressing on their neighbours.
But my question was not about IPv6. How do IPv4 routers operate in such a situation?
Regards, K.
exchange design 101. each connecting router interface is manually configured with an address of the exchange fabrics IP space. to establish peering, a router needs to know, at a minimum, the targets IP address and ASN - and while arp (if enabled) can get the target IP address, the ASN has to come via another channel - usually manually aquired. this is how the exchanges generally work, regardless of IP address family. more generally, where there are two or more egress routers from a broadcast domain, there will be problems -if- the routers know about each other -and- have the ability to try and set the exit rules for all other participants sharing the broadcast domain. Hence, with IPv6 and RA/ND, the idea of "preference" levels ... although in most cases I've experienced where there are multiple exit routers - that doesn't work either, since only subsets of the nodes on the shared media can use one or the other egress router. e.g. all the nodes don't fate-share. RA/ND was only an 80% solution anyway. --bill