To see all network devices:
ifconfig -a

To stop all network devices & restart them
/etc/init.d/networking restart

To show the routing & default gateway:
route
or
netstat -r

To refresh IP address from DHCP server
pump -i eth0 --renew

To view system events & messages
tail -f /var/log/messages
tail -f /var/log/syslog
(Use CTRL-C to exit tail)

I hope this helps.
James