(Loose) uRPF vs. non-announced IXP space

[Daniel Roesen]

On Wed, Feb 08, 2012 at 01:26:11PM +0000, Phil Mayers wrote:
> On 08/02/12 12:35, Stefan Neufeind wrote:
>
>> but why don't those routers source the ICMP-message from a
>> loopback-address or the like with an "official IP"?
>
> Section 2.2 of RFC 4443 suggests (to me) the default for source address of 
> ICMPv6 messages should be the address of the outgoing interface towards the 
> destination.

Which is operationally nonsense as it breaks traceroute. Luckily, most
vendors ignored that, or subsequently reverted to ingress interface as
source (e.g. Linux IIRC).

> Of course it's a SHOULD, so it's reasonable for an override option:
>
> ipv6 icmp source-address LoopbackX
>
> ...to exist. But not to be the default.

... which doesn't fix the underlying issue. Who says that routers do
have loopbacks within a globally advertised prefix?

Best regards,
Daniel

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