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

[Charles Howse]

Hi,
I've been having a devil of a time trying to resolve an issue with  
connectivity to the Internet.

Hardware setup:
ISP: Charter Communications, 2 megabit service
Cable Modem: Motorola SB4200 Surfboard
Router: Linksys Etherfast® Cable/DSL Router BEFSR41 V3 Firmware  
Version: 1.04.17
Computers: 2 FreeBSD 6.1-RELEASE. 1 Mac OS X 10.4.7, 100 baseT  
ethernet connections on all

Symptoms:
Not connected to the internet.  Pinging apple.com or charter.net,  
etc., times out.  Pinging other hosts, including 127.0.0.1, on the  
lan works.  Cable TV is always working when I can't connect.

The Charter tech has replaced my modem, and the cable from the ground  
block to the splitter under the house.  He has also split off the  
input cable under the house to the modem first, then another splitter  
to the TV's.

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?

--
Thanks,
Charles
http://bubbabbq.homeunix.net