Comment 2 for bug 132117

This appears to be wonky/different behaviour from the "ip" command (in some instances it displays the metric in the route print).

If you simply change the network-bridge script (line #62)
-vifnum=${vifnum:-$(ip route list | awk '/^default / { print $NF }' | sed 's/^[^0-9]*//')}
+vifnum=${vifnum:-$(netstat -arn | awk '/^0.0.0.0 / { print $NF }' | sed 's/^[^0-9]*//')}

everything should work as expected.