[Dibbler] Relay Configuration Problem

Jimmy Ott admin at onnet.ch
Thu May 19 10:50:13 CEST 2005

Hi Tomasz,

sorry that i never have a enjoyable mail for you :-/
i appreciate your work, and i know, you do that guy, and im sure that
i'm too stupid to set up the environment. i've tested now several things
which i want to tell you:

the relay was on a winxp machine, i reinstalled the whole system, and
tried it again, with same results, no nb solicitation message will be
sent from the relay, no nothing will be send from this one. but i saw
your new error message ;) thanks it's now clearer :) then i gave up the
winxp machine and installed debian gnu linux (sid), tried the client in
the same subnet as the server is, which works perfectly, set it to
another subnet and installed the relay.. now same results, relay did not
send any message out, no nb solicit. but there isn't the error "Send
failure detected (probably ICMPv6 Port Unreachable message received).
Are you trying to forward message to an invalid or unbound unicast
address?", the logentry shows "relay message to fd00:0:0:3::a", then
nothing happens, and the next entry is "Accepting message", because of
client retries to get an address.
your questions are answered below in text.

Tomasz Mrugalski wrote:
> On Wed, 11 May 2005 somebody known as Jimmy Ott wrote:
>> Hello and thanks for your answer,
>> just for your answer nr. 1
>> consequently we sniffed that before, there are only DHCPv6 solicit
>> messages (attached is a ethereal capture) from the client and no answer
>> from relay, so i think we misunderstood us. the relay receives the
>> dhcpv6 solicit message, but does not send any package out, nothing.
> Does relay send neighbor solicitation message after receiving DHCPv6
> solicit message? What exact version of the operating system are you
> running?

as mentioned above winxp sp2, no message sent out, pinging works to
unicast address.
same problems with debian unstable, pinging works, but no packets sent out.

> I have very few ideas why this does not work. But here are some hints:
> 1. I think that there might be a problem that noone has tried to force
> Dibbler to send a packet to a remote (i.e. not available on the local
> link) host. There's a way to quickly verify that theory:

> Configure your relay to use fake server address. Use locally available
> address of the router. Packet will be dropped, but that is not
> important. Reason for this is to verify whether relay will send packet
> or not.

i've set the relays server unicast address to my routers v6 address:
fd00:0:0:1::1... (relays address is built by router advertisements with
stateless autoconfiguration)
.. but also no packet was sent out.

> Please observe if relay tries to use neighbor discovery process
> (neighbor solicitation/neighbor advertisement messages). Meke sure to
> disable "dhcpv6" filters in ethereal if you use it.

yes, filters are disabled, only dhcvp6 solicit message from client is in
net :(

> 2. Could you try to run this relay under Linux? It would narrow the area
> of possible bugs.

yes, same results (but no unicast address unreachable error)

> 3. Install client on that stubborn host, which currently runs relay.
> Disable relay and configure client to use server unicast address. Will
> it send SOLICIT properly? Will it send anything at all?

i didn't find out how to configure client to use unicast server address,
tried with "unicast yes", but where should i configure the servers
address? i moved the client to the subnet where dhcpv6 server is, and
there dhcpv6 works great

> 4. Offtopic question: Have you investigated thet possibility to run
> DHCPv6 relays on Cisco routers?

yes, but waiting for the cisco guy which install me the newest IOS on my
labor routers :)

> If my suspicions are correct, fixing this might take some time as this
> requires to build small nework consisting of 4 nodes.
> Please, make this work. I'm really out of clues what's wrong :)

thank you very much for putting so much time to help me! i appreciate
your work very much!!
PS: my boss, silvia hagen, is now writing a second edition of the
oreilly's book "IPv6 Essentials", and i've got the job to write chapter
12, "get your hands dirty". if possible i will mention your great
project with a sample implementation, but surely not an ugly one like my
lab v6 implementation :-/

cheers jimmy

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