|
Routing to a subnet off the default route
![[nl]](/s/countries/nl.gif) Shadow Hawkins on Sunday, 16 October 2005 09:36:20
I am experimenting with IPv6, and learning how far it will stretch.
I have an "opera" LAN with an aiccu-connected router "phantom" on it, Naturally, "phantom" announces itself as the default router for IPv6.
On the same "opera" LAN, I have another router which routes to a wireless domain "hotspot". While "opera" runs on network #0, "hotspot" runs under #666. It is straightforward to route from "hotspot" through "opera" to "phantom" and up to the rest of the world.
"hotspot" <--ROUTER--> "opera" <--ROUTER-AICCU--> world
What I cannot seem to get working, is to announce "hotspot" on "opera". PC's connected to this LAN are not capable of auto-configuring a route to "hotspot". The problem being that "hotspot" is neither on-link nor on the route towards the default routes. If I announce the "hotspot" network it automatically becomes a default route. I cannot find the bits to toggle on the router advertisements that would allow auto-config routing from "opera" to "hotspot".
Am I correctly observing a problem here? Or is it simply a fact of life that all routes shall be structured hierarchically? Are there solutions, preferrably not of the kind "it happens to work on this particular OS"?
Thanks,
-Rick
Routing to a subnet off the default route
Router Advertisements is *NOT* a routing protocol. It adds a default route and that is it. With RA you can say 'this is the /64 on this link' + optional "use me for a default route", nowhere to say "I know where this prefix is", that is where routing protocols come into play, in this sitation I would think of RIP.
Best you can do in this setup is either:
1) setup a specific route on every host in operanet (not nice)
2) on the default router (routerA below) set a route to the hotspot network
3) run RIP, which still requires all the hosts to have a RIP client at least.
BTW: it is better to 'draw' networks like:
[ hotspot ] -- { wireless } -- [ routerW ] -- { operanet } -- [ routerA ] -- { internet }
{} = network
[] = host (routers are hosts with multiple interfaces)
Routing to a subnet off the default route
Shadow Hawkins on Friday, 21 October 2005 12:45:24
Router advertisement is indeed not usable to (re)direct routing.
What I was missing in Jeroen's reply (thanks!) is *why*, because
his suggestions contradicted with the feeling I had about
auto-config.
I have thus extended the hotspot with routing capabilities, using
the 2002::/16 network. Again, just to see how well this would work.
I am reporting my experiences in the hope that they will be useful
to others.
In the new situation, the hosts on the "opera" LAN receive two routable
prefixes -- one is the 2001::/16 prefix routed through sixxs, the
other is the 2002::/16 prefix routed through "hotspot". The latter
is routed according to RFC 3056 (to other 2002::/16 end points) and
RFC 3068 (a default router for non-2002::/16 destinations).
The result is wild and highly unadvisable.
The hosts on the "opera" LAN receive two prefixes, and choose the
path to traverse at random. If I want to access a 2002:IP4ADDR:: host,
it may choose to send from the 2001::/16 prefix, and vice versa. The
auto-configured hosts do not take the prefixes into account when routing,
because they do not see them as /16 prefixes; auto-configuration uses
/64 prefixes. As a result, trafic circulates from opera through hotspot,
through the 192.88.99.1 default routers for the 2002::/16 domain, to the
sixxs network, back to the local destionation host. What a waste of
resources!
My conclusion is that multiple prefixes should always come from routers
which are fully aware of all the locally available prefixes, and that
no routing decisions should be left to auto-configured hosts. Which is
exactly what Jeroen stated; but it is now clear to me why.
|
![[ch]](/s/countries/ch.gif)
on Sunday, 16 October 2005 11:19:49
Posting is only allowed when you are