Re: Dumb question about routing headers

Mark,

RPF has to be performed against an unicast address, one could use a somewhat hackish solutions ala RFC5496 though.
uRPF (RFC3704) is a commonly used technique to prevent packets to enter a router on a wrong interface (spoofed).

Cheers,
Jeff
On May 25, 2020, 2:43 PM -0700, Mark Smith <markzzzsmith@gmail.com>, wrote:
> Hi Ron,
>
> On Mon, 25 May 2020 at 13:56, Ron Bonica <rbonica@juniper.net> wrote:
> >
> > Inline…..
> >
> >
> <snip>
> >
> >
> >
> > A related question is are multicast addresses within the list if hops to visit valid?
> >
> >
> >
> > [RB] There is no rule against this, but there certainly should be!
> >
> >
>
> While I can't think of a use for multicast addresses in a source
> route, I don't think we should prohibit it yet without more thought.
> The multicast source address RPF check during multicast forwarding
> prevents multicast packets being sent back towards where they came
> from, so I don't think a forwarding loop using multicast addresses can
> be formed, even if specified in the routing header.
>
> If source address RPF checks were also universally performed for
> unicast packets at each forwarding point then I don't think the RFC
> 5095 attack could have occurred either, because the attack involves
> creating a path where packets are sent back towards where they came
> from, creating the forwarding loop.
>
> Regards,
> Mark.
>
>
> <snip>
>
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