DHCPv6 Option 18 (interface-id) relay problem (fwd)

Christian Kratzer ck-lists at cksoft.de
Thu Nov 8 13:56:46 UTC 2012


Hi,

On Thu, 8 Nov 2012, Andreas Hanke wrote:

> Hello Christian,
> 
> thanks a lot for the reply.
> 
> Do you know how I have to change my configuration?
> I couldn't find andy documentation for that...

your dhcp configuration should be fine with the host definition you posted. 
Why not just test to see if it works.  As I said it looks like it should work 
but I cannot say for sure.

You might want to run a packet capture to see if your dhcp requests actually 
contain the options you are looking for.

Greetings
Christian


> 
> Thanks in advance...
> 
> Andreas Hanke
> 
> 
> Hi,
> 
> On Wed, 7 Nov 2012, Andreas Hanke wrote:
> 
>> Hello together,
>> 
>> I am working on a problem with my ISC DCHP Version 4.2.4-P2 server for IPv6 
>> since a lot of days.
>> But I could not found a solution. So I hope someone could help me.
>> 
>> - Situation:
>> I have to discover the Host by an interface id to give him a fixed IP 
>> address.
>> This interface id will inserted by an DSLAM which is connected to a lot of 
>> DSL Modems.
>> The interface id is the identifier, on which physical port the DSL Modem is 
>> connected.
>> I like to use the host definition into my dhcp.conf:
>> example:
>> 
>> host ws {
>>        host-identifier option dhcp6.interface-id "Interface-ID: DSLAM01 eth 
>> 2/1/01/21"
>>        fixed-address6 2001:db8:1:1::701;
>> }
> 
> have you tried it out ? I would be interested in hearing the results.
> 
> A quick look at the dhcp6 code shows it does call find_host_by_option() to 
> find a host.
> This possible might do what you want but I am not 100% sure.
> 
> Greetings
> Christian
> 
> Am 08.11.2012 13:07, schrieb Andreas Hanke:
> 
> Hello Frank,
> 
> I don't like to use RADIUS with PPoE because the overhead of the DHCP
> traffic is slimmer and so have more performance.
> 
> Other ideas in the DHCP word?
> 
> thanks a lot
> 
> Andreas Hanke
> 
> Am 08.11.2012 13:00, schrieb 
> dhcp-users-request at lists.isc.org<mailto:dhcp-users-request at lists.isc.org>:
> 
> 
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> Today's Topics:
>
>   1. RE: DHCPv6 Option 18 (interface-id) relay problem (Frank Bulk)
>   2. Re: DHCPv6 Option 18 (interface-id) relay problem
>      (Christian Kratzer)
> 
> 
> ----------------------------------------------------------------------
> 
> Message: 1
> Date: Wed, 7 Nov 2012 19:41:01 -0600
> From: "Frank Bulk" <frnkblk at iname.com><mailto:frnkblk at iname.com>
> To: <dhcp-users at lists.isc.org><mailto:dhcp-users at lists.isc.org>
> Subject: RE: DHCPv6 Option 18 (interface-id) relay problem
> Message-ID: 
> <000801cdbd52$1c2e80b0$548b8210$@iname.com><mailto:000801cdbd52$1c2e80b0$548b8210$@iname.com>
> Content-Type: text/plain; charset="iso-8859-1"
> 
> Can you use RADIUS instead?
> 
> 
> 
> Frank
> 
> 
> 
> From: 
> dhcp-users-bounces+frnkblk=iname.com at lists.isc.org<mailto:dhcp-users-bounces+frnkblk=iname.com at lists.isc.org>
> [mailto:dhcp-users-bounces+frnkblk=iname.com at lists.isc.org] On Behalf Of
> Andreas Hanke
> Sent: Wednesday, November 07, 2012 1:52 AM
> To: dhcp-users at lists.isc.org<mailto:dhcp-users at lists.isc.org>
> Subject: DHCPv6 Option 18 (interface-id) relay problem
> 
> 
> 
> Hello together,
> 
> I am working on a problem with my ISC DCHP Version 4.2.4-P2 server for IPv6
> since a lot of days.
> But I could not found a solution. So I hope someone could help me.
> 
> - Situation:
> I have to discover the Host by an interface id to give him a fixed IP
> address.
> This interface id will inserted by an DSLAM which is connected to a lot of
> DSL Modems.
> The interface id is the identifier, on which physical port the DSL Modem is
> connected.
> I like to use the host definition into my dhcp.conf:
> example:
> 
> host ws {
>        host-identifier option dhcp6.interface-id "Interface-ID: DSLAM01 eth
> 2/1/01/21"
>        fixed-address6 2001:db8:1:1::701;
> }
> 
> 
> 
> - My setup:
> Client PC with DSL Modem <-------------> DSLAM which is inserting a option
> 18 with the interface id <-----------> CISCO 7606-S Router which have a
> helper at the interface which is connected to the DHCP server. This helper
> forward the DCHP Message to the DHCP server and works as a relay
> <-----------> ISC DCHP server for IPv6
> 
> - Parts of my server configuration:
> ----------------------------------------------------------------------------
> -------------------------------------------------------
> # Please see:
> http://www.ipamworldwide.com/dhcp-options/isc-dhcpv6-options.html
> #This function logs the DHCPv6 client id, which means the Link Local Address
> (Option 1)
> log(info,concat("Client-ID: " , binary-to-ascii(16,8,"-",option
> dhcp6.client-id)));
> #This function logs the DHCPv6 interface id, which means the port of the
> DSLAM (Option 18)
> log(info,concat("Interface-ID: " , option dhcp6.interface-id));
> ----------------------------------------------------------------------------
> -------------------------------------------------------
> 
> - My problem:
> The ISC DHCP server could not discover the interface-id (Option 18), which
> is inserted by the DSLAM -> get no log message (see configuration).
> The client-id (Option 1), which is inserted by the Client PC with DSL Modem
> works fine -> get log message (see configuration).
> 
> I tested it without CISCO and without DSLAM/DSL Modem direct connect over an
> Networkswitch and inserting the interface-id (Option 18) by the Client PC,
> that works -> get log message (see configuration).
> 
> After that I analysed the TCP packets. What I found out is, that the
> difference is that:
> - Message type "RELAY-FORW (12)" with CISCO and DSLAM/DSL Modem:
> <field name="dhcpv6.msgtype" showname="Message type: Relay-forw (12)"
> size="1" pos="62" show="12" value="0c"/>
> - Message type "SOLICIT (1)" without CISCO and DSLAM/DSL Modem:
> <field name="dhcpv6.msgtype" showname="Message type: Solicit (1)" size="1"
> pos="62" show="1" value="01"/>
> 
> Side information:
> If I configured an ipv6 range without host definitions into my dhcp.conf the
> Client PC get in both situations an ip6 address.
> 
> Could you tell me if the message type is the problem and if yes what I have
> to change?
> If no, what went wrong?
> 
> I have attached the both network packets with situation 1 "with CISCO and
> DSLAM" and situation 2 "without CISCO and DSLAM".
> 
> 
> Thanks a lot for your help!
> 
> 
> 
> 
> 
> 
> 
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-- 
Christian Kratzer                      CK Software GmbH
Email:   ck at cksoft.de                  Wildberger Weg 24/2
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Web:     http://www.cksoft.de/         Geschaeftsfuehrer: Christian Kratzer


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