[c-nsp] Bridge devices - ARP takeover

Rodney Dunn rodunn at cisco.com
Thu Aug 13 15:08:06 EDT 2009


I can't follow the problem.

The router should try to defend the mac address it owns but if another 
device simply takes over for it the only way to resolve that is fix that 
device.

How exactly is it taking over?
What is the topo (ascii diagram would work).

Rodney



Graham Wooden wrote:
> Hi there,
> 
> I have a customer hanging off of my edge router (6509/Sup32/12.2.33SXI), 
> doing a Point-to-Point wireless shot from the DC to another site.
> On myside, it's a L3 VLAN doing a /30 to a smaller Cisco router on the 
> other end. I am then statically routing some additional subnets to the 
> far end router.
> 
> After about 30 minutes of the link being powered up, the MAC address of 
> local Radio appears to take over the /30, and hence all routing breaks.  
> To fix this, seems to that if I hardcode the MAC that belongs to the 
> Cisco router on the far, all seems good and traffic keeps on trucking. 
> The other fix that was being done until the hardcode went into affect, 
> was power cycling the local radio.
> 
> My question is this:  While the hardcoding seems to be the trick to 
> solve this, is there another command, maybe on the interface to achieve 
> this fix too?
> I have yet to find out from the customer if there are any MAC/ARP 
> settings in his radios and that could be doing take over on purpose.
> 
> I am hoping that I can curb this type of behaviour without getting him 
> involved.
> Thoughts to this?  Thanks,
> 
> -graham
> 
> 
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