> -----邮件原件----- > 发件人: Ted Lemon [mailto:[email protected]] > 发送时间: 2010年8月15日 1:15 > 收件人: Xu Xiaohu > 抄送: 'Ole Troan'; [email protected]; [email protected] > 主题: Re: [dhcwg] Is tunnelling DHCP multicast messages in 6rd unicast tunnel > to BR acceptable for DHCP redundancy?//re: [Softwires] About > draft-guo-softwire-6rd-ipv6-config-00 > > On Aug 8, 2010, at 11:59 PM, Xu Xiaohu wrote: > > In addition, in case that the DHCP > > server/relay on a given BR is unavailable due to some reason (e.g., no > > available address in the pool) but the other functions of it (e.g., the > > anycast route for it) are still available, once the DHCP message is tunneled > > to that BR, the DHCP service is unavailable any more. That's to say, it's > > hard to achieve the high availability for DHCP servers/relay agents since > > the DHCP information-request can not be relayed to other DHCP > > servers/relays. > > I don't see the problem here. If you want redundancy, you should configure > each BR to relay to more than one DHCP server. This would be the default anyway, > according to RFC3315 section 20, which requires the relay to multicast if not > otherwise configured.
However, the BR itself (no matter as a relay agent or a DHCP server) is a single point of failure, especially in the case where the DHCP service on the BR is unavailable while the route for it (anycast address) is still OK. > > 2) The CPE as a DHCP relay agent sends the DHCP-relay-forward message to one > > of the learnt DHCP server (unicast) addresses. Since 6rd can support unicast > > flexible, the DHCP server can be located either on/behind any BR or behind > a > > 6rd CPE which is owned by the 6rd SP. > > This is completely contrary to the recommendations in RFC3315, which require > the client to multicast, and require any relays to multicast by default. > Trying to relay DHCPv6 traffic over an IPv4 transport seems needlessly > complicated. You have the tunnel--why not use it? Yes, the CPE could directly tunnel the DHCP request messages (multicast) received from the clients to the nearest BR. However, since the source addresses of these DHCP messages are link-local addresses, how could the BR return the corresponding DHCP reply messages to the clients in the 6rd scenario? Best wishes, Xiaohu _______________________________________________ Softwires mailing list [email protected] https://www.ietf.org/mailman/listinfo/softwires
