On 2 jan 2008, at 19:44, Mark Smith wrote:
Maybe I'm missing something really obvious, but how are operators and their helpdesks going to be able to troubleshoot customer connectivity problems via offlink ping or traceroute if the link between the customer and the upstream infrastructure only has link locals?
When a packet is to be generated and sent out on a link local addressed interface towards a non link local destination, a source address is borrowed from another interface without explicitly configuring "ipv6 unnumbered" (although Cisco IOS will let you do that, too).
PMTUD won't work either
Hm, yes, if the LAN behind the CPE uses smaller packets than the WAN link to the ISP. (Which is actually true for my DSL line, which has a 4470 byte ATM MTU but both my router and my ISP's only support 1500 on the LAN side.)
A ULA prefix on that upstream link would address some of the issues
No, that would break pretty much all the stuff you mentioned without the automatic borrowing of a global address.
I think to provide global Internet access you really need to ensure a fully globally addressed path to and from the Internet.
If you do DHCPv6 prefix delegation it seems a bit much to also assign an address. But if you have RAs anyway to support the case where the CPE bridges rather than routes, you get the global address for free.
Iljitsch