by default Oracle VM use the bond0 to the first interface configured, this is an advantage (used for fault tolerant network).
So the bond0 is not a problem.
and to solve your problem verify that your server is connected to the gateway (physically) and also verify your configuration that should looks like:
BONDING_OPTS="mode=0 miimon=250 use_carrier=1 updelay=500 downdelay=500 primary=eth0"
#This file was dynamically created by OVM manager. Please Do not edit
I hope this can help you