Date: Sun, 20 Mar 2011 14:10:07 -0400 From: Stephen Clark <sclark46@earthlink.net> To: "Eugene M. Zheganin" <eugene@zhegan.in> Cc: freebsd-net@freebsd.org Subject: Re: ipv6, stateful config and non-default prefixlen Message-ID: <4D8642FF.6050400@earthlink.net> In-Reply-To: <4D846A9C.7000705@zhegan.in> References: <4D8370AB.1070000@zhegan.in> <20110318.195636.74687196.sthaug@nethelp.no> <4D846A9C.7000705@zhegan.in>
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On 03/19/2011 04:34 AM, Eugene M. Zheganin wrote: > Hi. > > On 18.03.2011 23:56, sthaug@nethelp.no wrote: >> Are you using IA_PD or IA_NA on your DHCPv6 server? > Since I didn't configure anything on a DHCPv6 server about PD, I > assume I'm using NA. > >> rtadvd can give you the default router. >> >> DHCPv6 IA_NA gives you a single /128 address and no netmask. >> >> DHCPv6 IA_PD gives you a prefix (with the netmask of your choice), but >> I don't know whether FreeBSD can (easily) use this. > I don't see a relation between these 2 things. Prefix delegation is > used to assign prefixes to client _routers_, without knowing about the > topology. I'm configuring a _workstation_. I don't need a prefix to > assign addresses to other computers, I don't have a network behind > this workstation, I need to know about my prefix, and I have that > information in ndp cache, although it is somehow useless. > >> As mentioned, DHCPv6 IA_PD gives you a prefix. And ISC dhclient can ask >> for it, see the the -P option. > "The Prefix Delegation options provide a mechanism for > automateddelegation of IPv6 prefixes using the Dynamic Host > Configuration Protocol (DHCP). This mechanism is intended for > delegating a long-lived prefix from a delegating router to a > requesting router, acrossan administrative boundary, where the > delegating router does not require knowledge about the topology of the > links in the network to which the prefixes will be assigned." And > that's from RFC. > >> If you use DHCPv6 IA_NA, you receive a single /128 address (it is /128 >> by definition, the DHCP answer doesn't include a netmask). > That seems to be a mistake. Look what explanation I found in the ietf > maillist: > > "Interface addresses are completely SEPARATE from routing > information.Please do NOT confuse the two. This has been a source of > confusion formany IPv6 implementors who know IPv4.The configuration of > addresses for an interface MUST NOT be tied to the configuration of > prefix information for routing. Just because a prefix is on a link, > does not mean the interface necessarily has an address for that prefix > (it may have none, 1, or many). Just because an interface has an > address, does not mean that the system has any prefix information for > a prefix that "contains" that address. Prefix information and > addresses assigned to interfaces are completely separate." > > So it's just an address. Not a /128, just an address. > >> You should *not* expect to reach other computers on the link >> through such a /128 >> address > So, in other words, DHCPv6 is useless. No, I don't think so. I have a > bunch of windows on the same link, working with the same DHCPv6 > server, and doing just fine. And that's sad, because I used to think > that FreeBSD is always a queen of the network, far ahead of the > non-truly-networked OS bunch. I'm still hoping that this /64 prefix > issue is related to my low knowledge. > > P.S. And I know that autoconfiguration won't work on a link with /120. > And of course, THAT is the reason why I'm using the DHCPv6. > > Eugene. > _______________________________________________ > freebsd-net@freebsd.org mailing list > http://lists.freebsd.org/mailman/listinfo/freebsd-net > To unsubscribe, send any mail to "freebsd-net-unsubscribe@freebsd.org" > How does a router that is using dhclient to get delegated a address prefix from an upstream router obtain its default route, since dhcpv6 can't provide a default route. And since it is a router it can't get its default route from router advertisements from the upstream router? -- "They that give up essential liberty to obtain temporary safety, deserve neither liberty nor safety." (Ben Franklin) "The course of history shows that as a government grows, liberty decreases." (Thomas Jefferson)
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