Re: IPv6 nexthop for IPv4

2015-03-26 15:29 GMT+01:00 Sowmini Varadhan [off-list ref]:

On Thu, Mar 26, 2015 at 9:16 AM, Bjørnar Ness [off-list ref] wrote:

quoted

Hello, hope this is the right place to ask.

Does anyone know if there is work beeing done in natively supporting
IPv6 nexthops for IPv4?

What problem are you trying to solve? Do you want to tunnel your
ipv4 packet through IPv6? there are a number of tunneling mechanisms
in linux for this.

No, no tunneling, just route the packet directly as-is to the ipv6 nexthop

quoted

I know that "some" Linux switch software company is working on this, but
I am afraid the functionality will be more of a "hack".

The benefit of this is stateless configuration (rfc5549), using IPv6 link-local
neighbor address as IPv4 nexthop, beeing able to do for example:

ip route add 10.0.0.0/16 via fe80::225:90ff:fed3:bfb4/64 dev sfp0

Trying to understand what the desired behavior is, for the route
above: if I send a packet from 10.0.0.1 to 10.0.0.2, you want the dst-mac
to be the mac address of e80::225:90ff:fed3:bfb4???

Absolutely, correct.

how do you know that fe80::225:90ff:fed3:bfb4 supports ipv4
forwarding on the receiving interface (and if it does, why didn't it
advertise itself as an IPv4 router on that interface)?

Basically because you either added the route manually, or it was provided
by fe80::225:90ff:fed3:bfb4 itself via some routing protocol (MP-BGP)

This will be the same as any other route. How do you know it forwards traffic..

In large routed setups, address management in general and lack of IPv4 addresses
can become a big hassle. Beeing able to get a ipv6 neighbor for a ipv4
route would
make this process a lot simpler.

-- 
Bj(/)rnar