DHCPv6 Option 18 (interface-id) relay problem

Christian Kratzer ck-lists at cksoft.de
Thu Nov 8 10:41:51 UTC 2012


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.


> - 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!
> --
> Regards
> Andreas Hanke
> IP Network Operations
> andreas.hanke at r-kom.de<mailto:andreas.hanke at r-kom.de>
> http://www.r-kom.de
> ________________________________
> R-KOM Regensburger Telekommunikationsgesellschaft mbH & Co. KG,
> Kommanditgesellschaft, Sitz Regensburg, Registergericht Regensburg,
> HRA 5818
> Persönlich haftende Gesellschafterin und Geschäftsführung:
> R-KOM Regensburger Telekommunikationsverwaltungsgesellschaft mbH,
> Sitz Regensburg, Registergericht Regensburg,
> HRB 6764; Geschäftsführer: Dipl.-Inf. (FH) Alfred Rauscher

Christian Kratzer                      CK Software GmbH
Email:   ck at cksoft.de                  Wildberger Weg 24/2
Phone:   +49 7032 893 997 - 0          D-71126 Gaeufelden
Fax:     +49 7032 893 997 - 9          HRB 245288, Amtsgericht Stuttgart
Web:     http://www.cksoft.de/         Geschaeftsfuehrer: Christian Kratzer

More information about the dhcp-users mailing list