Cisco WLAN controller 4400 and dhcp relay

[wlanmac]

It's in subversion...

http://www.coova.org/CoovaChilli/Developers


On Wed, 2009-07-08 at 10:32 +0200, karczewski cyrill wrote:
> Hi!!!
> You are a master DAVID!!
> 
> Where could i find this version?
> 
> Thank you very much.
> 
> Cyrill KARCZEWSKI
> Service Informatique
> Hôpital Saint-Louis
> 1 Avenue Claude Vellefaux
> 75010 PARIS
> 0142499208
> 
> ----- Message d'origine -----
> De: wlanmac <wlan at mac.com>
> Date: Mardi, Juillet 7, 2009 9:22 pm
> Objet: Re: Cisco WLAN controller 4400 and dhcp relay
> À: chilli at coova.org
> 
> 
> > I updated the Subversion with the latest changes.. I checked the ARP
> > replies... looks like I already fixed it. 
> > 
> > The new chilli does some things a bit differently. You'll find a new
> > utility, called chilli_opt, which is the only binary that is linked with
> > the configuration parsing (code generated by gengetopt). chilli server
> > will launch this to parse out and build up a binary configuration file.
> > chilli server will then re-read this configuration file, loading in the
> > new configuration without any delays (no more stalling for DNS
> > lookups). 
> > 
> > Enjoy,
> > David
> > 
> > 
> > On Mon, 2009-07-06 at 11:38 +0200, Thomas Liske wrote:
> > > Hi,
> > > 
> > > karczewski cyrill wrote:
> > > > Hello everyone!! I hope you are fine!!
> > > > 
> > > > I have a problem with coova-chilli 1.0.13 and i will be so 
> > gratefull for anyone find a solution.
> > > > 
> > > > I use a cisco WLAN controller 4400 with vlans configured. in order 
> > to transmit dhcp requests in that vlan, cisco has a dhcp relay.
> > > > 
> > > > the problem is that before transmit dhcp requests to chilli, the 
> > cisco controller does an ARP request to chilli.
> > > > 
> > > > Chilli reply, but the cisco controller doesn't like this answer.
> > > > 
> > > > In fact, when chilli reply, in the ARP target address field, 
> > chilli put 0.0.0.0 instead of the cisco controller ip address. It send 
> > the ARP reply in broadcast mode.
> > > > 
> > > > So, the cisco controller send an ARP request again and again...
> > > > 
> > > > here is the cisco request:
> > > > 
> > > > http://picasaweb.google.com/cyrill51/Chillispot#5355257375354395602
> > > > 
> > > > here is the reply
> > > > 
> > > > http://picasaweb.google.com/cyrill51/Chillispot#5355257377945980914
> > > > 
> > > > Anyone has an idea to correct this in chilli or in the cisco controller.
> > > > 
> > > 
> > > it seems to be an issue on the WLC implementation. According to 
> > RFC826 
> > > the WLC should accept the arp reply with an zero target address:
> > > 
> > > 
> > > ==============================[RFC826]==============================
> > > ?Do I have the hardware type in ar$hrd?
> > > Yes: (almost definitely)
> > >    [optionally check the hardware length ar$hln]
> > >    ?Do I speak the protocol in ar$pro?
> > >    Yes:
> > >      [optionally check the protocol length ar$pln]
> > >      Merge_flag := false
> > >      If the pair <protocol type, sender protocol address> is
> > >          already in my translation table, update the sender
> > > 	hardware address field of the entry with the new
> > > 	information in the packet and set Merge_flag to true.
> > >      ?Am I the target protocol address?
> > >      Yes:
> > >        If Merge_flag is false, add the triplet <protocol type,
> > >            sender protocol address, sender hardware address> to
> > >           the translation table.
> > >        ?Is the opcode ares_op$REQUEST?  (NOW look at the opcode!!)
> > >        Yes:
> > > 	Swap hardware and protocol fields, putting the local
> > >             hardware and protocol addresses in the sender fields.
> > > 	Set the ar$op field to ares_op$REPLY
> > > 	Send the packet to the (new) target hardware address on
> > >             the same hardware on which the request was received.
> > > ==============================[RFC826]==============================
> > > 
> > > There are no checks on the target address for ARP replies. The arp 
> > reply 
> > > is btw not send as a broadcast, there is the WLC's ARP address 
> > specified 
> > > as the destination address in the ethernet header.
> > > 
> > > I'd just checked Linux's implementation on sending ARP replies, it 
> > sets 
> > > the target IP address to the original request source address. Maybe 
> > it 
> > > should be fixed in cc to perform as other common ARP implementations 
> > 
> > > perform.
> > > 
> > > 
> > > Regards,
> > > Thomas
> > > 
> > 
> > 
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