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(usagi-users 03912) Re: Binding Update Failure

I tried two setups.  The first setup had both routers and the HA at
the same location with the HA sending out router advertisments for
homenet and the foreign router sending out router advertisments for
visitnet.  Once the mobile node was booted up, as expected, it began
switching back and forth between the two networks each time it
received a router advertisement from either one of them.

The second setup split two wireless networks apart.  The MN was booted
in homenet and then moved into visitnet.  At this point, the MN did
not pick up the router advertisement from the foreign router and bind
into the new network.  It only did so once I manually forced the MN
into the network with "iwconfig ath0 essid visitnet."  I am unsure
what is causing this.  I have attached the two radvd.conf's below:

HA radvd.conf:
interface ath0{
 AdvSendAdvert on;
 MaxRtrAdvInterval 10;
 MinRtrAdvInterval 3;
 AdvIntervalOpt off;
 AdvHomeAgentFlag on;
 AdvHomeAgentInfo on;

 prefix 2001:106:2700::2/64
     AdvRouterAddr on;
     AdvOnLink on;
     Autonomous on;

Foreign Router radvd.conf:
# br0 -> bridge interface on the AP
interface br0{
 AdvSendAdvert on;
 MaxRtrAdvInterval 10;
 MinRtrAdvInterval 3;
 AdvIntervalOpt on;
 AdvHomeAgentFlag off;

 prefix 2001:106:1100::1/64
     AdvRouterAddr on;
     AdvOnLink on;
     AdvAutonomous on;

Thanks for all the help.


On 7/20/07, Romain KUNTZ <kuntz@xxxxxxxxxxxxxxxxxxxxx> wrote:
Hi Ryan,

On 2007/07/20, at 2:15, Ryan Measel wrote:
> I tried a new setup today with the routers separated down the fall
> from each other so that the wireless networks overlap just a bit.
> Both wireless networks are on a separate ESSID (homenet and visitnet).


> I had both of the networks on the same channel though.  Is it
> necessary or preferred to have the routers on different channels?

This is bad. If both APs are on the same channel, you'll have noise
and interferences between both APs. Every AP whose coverage overlaps
with another must use nonoverlapping independent channels (usually
channels 1, 6 and 11 are used).

> How > does the MN receive router advertisements from the AR if it is > listening for its own router on a different channel?

The MN can't listen to 2 AP at the same time with a single WiFi card.
The MN actually listens to the AP it is attached too, and for example
when the link quality is too low (or for your test you can force the
MN to associate with another AP by doing "ifconfig ath0 essid
visitnet" for example), it tries to associates with a different AP on
a different channel. Then the MN receives the new RA, and the layer 3
handover procedure is launched. That's why in Mobile IPv6, L3
handovers can take several seconds. Some solutions such as using
multiple interfaces (for example MCoA) can reduce greatly the L3
handover time. But first, let's have a simple MIPv6 testbed running :-)

> In addition, the
> routers are set to master (ap) mode and the HA and MN are in managed
> mode.   Would it be better to put everything in ad-hoc?

No no, current configuration (master and managed mode) is the only
mode you can use for a MIPv6 Testbed. Ad-hoc mode is another story.

> When I gave this setup a try, it partially succeeded.  The MN did
> successfully bind into the foreign network a couple times, but failed
> considerably more.  The issue was that router advertisements from both
> the HA and AR were being received in both wireless networks.  The MN
> is receiving both of these from either the HA or the AR (depending on
> which network it resides in at the time), and the MN is out of range
> of which ever network it is not in.  Hence, the router advertisements
> are being forwarded between the networks.  IPv6 forwarding
> (/proc/sys/net/ipv6/conf/forwarding) is set to 1, but Accept RAs
> (/proc/sys/net/ipv6/conf/accept_ra) is set to 0 on the HR, HA, and AR.
> This is very confusing because I did not believe routers were suppose
> to forward router advertisements.  I suppose it is possible just
> because I am using normal nodes with a bridge as access points, as
> opposed to true routers.  Is there another way to prevent router
> advertisements from being forwarded?

Hmm I do not completely understand your network topology, and RA are
not supposed to be routed by routers. Maybe you could send some ascii
drawing with some information such as where are the routers, who is
sending RAs, where are the APs.

FYI, every different IP link must be separated from the other one
with an IP Router. This router sends different RA on each link. One
AP can be placed on each link playing the role of a bridge.


> On 7/19/07, Romain KUNTZ <kuntz@xxxxxxxxxxxxxxxxxxxxx> wrote:
>> Hi Ryan,
>> On 2007/07/19, at 5:53, Ryan Measel wrote:
>> > I am still having issues with the mobile node not being able to
>> bind
>> > to the home agent.  It knows that it moves into a foreign
>> network, but
>> > it then throws an error that "blackhole is already set."  And, no
>> Do not pay attention to this message, this is juste a debug message
>> that ii IMHO not the cause of your problem.
>> > binding update will be sent.  I have posted the debug from the
>> mobile
>> > node and the config file for the mobile node below.
>> Ok, see my comment inline below.
>> > Also, how does everyone else setup their testbed, i.e., what
>> type of
>> > hardware do use for routers and the home agent?
>> Personnally, I use some usual desktop PCs for the HA, MR, Access
>> Routers.
>> > Mobile Node Debug Output
>> > =====================
>> [snip]
>> > Wed Jul 18 23:32:38 mn_move: 1578
>> > Wed Jul 18 23:32:38 mn_move: in foreign net
>> [snip]
>> > Wed Jul 18 23:32:39 mn_move: 1578
>> > Wed Jul 18 23:32:39 mn_move: in home net
>> [snip]
>> > Wed Jul 18 23:32:44 mn_move: 1578
>> > Wed Jul 18 23:32:44 mn_move: in foreign net
>> [snip]
>> > Wed Jul 18 23:32:45 mn_move: 1578
>> > Wed Jul 18 23:32:45 mn_move: in home net
>> [etc...]
>> Looks like your MN moves to the Home Network right after (1 sec.)
>> finding a foreign network. I think it does not send any BU because it
>> does not have the time to send one :-)
>> How do you performs handovers? Are your APs configuration OK
>> (different channel and ESSID, etc.)?
>> Cheers,
>> romain

Romain KUNTZ
Louis Pasteur University - Networks and Protocols Team