[X-Unix] How to determine which network component is failing

[Dennis Fazio]

On Jul 23, 2006, at 8:03 AM, Charles Howse wrote:

> This morning, I was offline, and just by accident decided to try  
> and release and renew the ip address using the web interface of the  
> router.
> BINGO!  Online again!
>
> Is this an indication that the router is not noticing that the  
> lease has expired on my dhcp assigned ip address from the modem?   
> Or is it an indication that the modem is not renewing it's ip  
> address?  Or is it something else?
>
> Can I tell the router to release / renew the ip address from a  
> shell script?

I'm not familiar enough with things to say what your problem might be  
from your description.

But, you can verify if you got a good IP address in the network  
preferences panel. There is a button there to also renew your DHCP  
lease. Often turning airport off and on or disonnecting and  
reconnecting the ethernet cable triggers things also. When the  
connection is working, do a traceroute to get the IP of the cable  
modem and the next upstream hop. Then you can progressively ping  
through the path to see where things are failing (LAN or cable modem/ 
upstream path).

You can also just assign static addresses to your computers if you  
think DHCP is being problematic. That will isolate whether the  
problem is connectivity/routing or address assignment. I find  
BwanaDik is a good tool for determining if you have good internal and  
external addresses set.

--
Dennis Fazio
dfz at mac.com