Odd networking problem

[Michael Galea]

On 18/03/11 11:36 PM, William Park wrote:
> On Fri, Mar 18, 2011 at 11:22:33PM -0400, Peter King wrote:
>> Here's one for the experts.
>>
>> I have a netbook running OS X. The ethernet connection to my router is reported
>> to be good, but I can't ping the router, much less connect to the net. Nor can I
>> see the netbook from other computers on the LAN.
>>
>> Normally, I'd think this was a DNS problem. As far as I can tell (I don't know
>> much about OS X), it isn't; the nameservers work for all the other computers on
>> the network, so they should be okay.
>>
>> Routing? Well, according to netstat -nr, the default route does have the IP address
>> of the router. I tried adding the default route manually anyway, just to see, but
>> no difference.
>>
>> At this point I'd suspect the cables or the hardware. The cables work fine with
>> other computers, though. To check the hardware on the netbook I put sysrescuecd
>> on a USB stick and booted from that. The ethernet connection runs perfectly with
>> no fuss or feathers at all.
>>
>> Now I'm at that place known to us all: Wit's End. Any suggestions for what to try
>> next? (Other than "install Linux instead of OS X" -- it's my daughter's computer,
>> not mine, otherwise I would have done that long ago.)
>
> Firewall?  Try 'traceroute'.
Hey William,
Are you sure the netbook's netmask is correctly configured?

Does tcpdump on the nameserver show incoming traffic when you ping from 
the netbook? Try tcpdump with -e.
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