how can I find the default gateway of an ubuntu box
Look for a line that says something like:
default 10.63.3.254 0.0.0.0 UG 0 0 0 eth0
The second column contains the default gateway, and the last column is the interface.
You can also use the ip command:
which will give you something like
default via 10.63.3.254 dev eth0
You can also use "netstat -nr" (I usually leave the n in the flags, so as to not have to wait for host resolution if there's a DNS issue).
grog:/var/log# route -n Kernel IP routing table Destination Gateway Genmask Flags Metric Ref Use Iface 192.168.1.0 0.0.0.0 255.255.255.0 U 0 0 0 eth0 0.0.0.0 192.168.1.1 0.0.0.0 UG 0 0 0 eth0
You can also check /etc/network/interfaces to see what it'll be on next reboot or networking restart.