Stig, Wrt to this question you raised:
"Can you manually configure prefix on a host without also specifying prefix length?" See text below snipped from http://www.microsoft.com/technet/community/columns/cableguy/cg0506.mspx#EMB about Manual configuration for Windows Vista for IPv6. Text snipped from this URL shows that if an IPv6 address has been added via the CLI, prefix length is optional to be configured. Also, as I said before, I not too fond of a host assuming a default of 64 as this CLI help shows. ------------------ begin snip------------------------------- Configuring IPv6 With the Netsh.exe Tool In the same way as IPv6 for Windows XP, you can configure IPv6 addresses and other configuration parameters at the command line using commands in the netsh interface ipv6 context. Configuring Addresses To configure IPv6 addresses, you can use the netsh interface ipv6 add address command with the following syntax: netsh interface ipv6 add address [interface=]Interface_Name_or_Index [address=]IPv6_Address[/Prefix_Length] [[type=]unicast|anycast] [[validlifetime=]Time|infinite] [preferredlifetime=]Time|infinite] [[store=]active|persistent] * interface The connection or adapter's name or interface index. * address The IPv6 address to add, [optionally followed by the subnet prefix length] (default of 64). ------------------------ end snip ------------------------------------------------------------------------------------- Hemant -----Original Message----- From: Stig Venaas [mailto:[EMAIL PROTECTED] Sent: Friday, June 29, 2007 11:54 AM To: Hemant Singh (shemant) Cc: Ralph Droms (rdroms); JINMEI Tatuya / ????; IETF Mailing List IPv6 Subject: Re: draft-wbeebee-nd-implementation-pitfalls-00 with urgent changessuggested to 2462bis-08 Hemant Singh (shemant) wrote: > Please see in line below with "<hs>" > > -----Original Message----- > From: Ralph Droms (rdroms) > Sent: Friday, June 29, 2007 10:26 AM > To: JINMEI Tatuya / ???? > Cc: IETF Mailing List IPv6; Wes Beebee (wbeebee); Hemant Singh > (shemant) > Subject: Re: draft-wbeebee-nd-implementation-pitfalls-00 with urgent > changessuggested to 2462bis-08 > > > On Jun 28, 2007, at Jun 28, 2007,1:14 AM, JINMEI Tatuya / 神明達哉 > wrote: > >> At Wed, 27 Jun 2007 14:27:37 -0400, >> Ralph Droms <[EMAIL PROTECTED]> wrote: >> >>> One bug that may or may not be common is to make assumptions about >>> the prefixes on a link based on addresses assigned to an interface. >>> I can imagine (and I believe we've actually made a real sighting of >>> this scenario) that an IPv6 implementor might extrapolate IPv4 >>> conventions and extract the /64 prefix from an assigned address >>> (either SLAAC, DHCP or manual config), and add a route to the host >>> table indicating that the prefix is on-link, regardless of whether >>> the prefix is advertised as "on-link" in an RA. >> [...] >> >> If the system administrator manually configures an IPv6 address with >> a prefix length smaller than 128, the kernel will assume that the >> corresponding prefix is on-link. But I believe this should be >> reasonable. >> >> JINMEI, Tatuya >> Communication Platform Lab. >> Corporate R&D Center, Toshiba Corp. >> [EMAIL PROTECTED] > > I see where draft-wbeebee-nd-implementation-pitfalls also mentions manual > configuration as a special case: > > 2. The RA and ICMPv6 Redirects from the default router are the only > sources of information for on-link determination. DHCPv6 or any > other configuration on the host MUST NOT be used for on-link > determination. Manual configuration of a host introduces its own > set of security considerations and is beyond the scope of this > document. > > Is there some reason to believe the information about on-link prefixes should > be implicitly overridden in the case of manual address assignment? I can > understand explicitly overriding information from RAs by manually configuring > the on-link information as a separate step from manual address assignment. > But it seems to me that assuming the prefix from a manually configured > address is on- link might cause unexpected loss of connectivity if the prefix > does require off-link delivery through the router. At least as a sysadmin/user I would find it confusing if the prefix length I configured would not be used for on-link determination. I think it's more bad than good to try to separate the two. I'm happy the way it currently is on the systems I've seen. > > <hs> If the host has been manually configured for IPv6 address where the host > was also configured for prefix and prefix length, then what's on-link for > this host can be determined by host. But what if manual configuration > configured an IPv6 address and maybe, also the prefix, but forgot to > configure prefix length. Then this manual configuration has no means to > determine what's on-link for a destination based on the data from manual > configuration. I have host not assuming a default prefix length yet. The RA > has been explicitly ignored. So not this host has no choice but to send > non-link-local traffic to the default router. Specifying manual configuration > behavior and its interaction with RA is a can of worms that will take time to > clear up. Can you manually configure prefix on a host without also specifying prefix length? Stig > > Hemant > > - Ralph > > > -------------------------------------------------------------------- > IETF IPv6 working group mailing list > ipv6@ietf.org > Administrative Requests: https://www1.ietf.org/mailman/listinfo/ipv6 > --------------------------------------------------------------------
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