There are circumstances when AIX will let you define two default routes. I think this is bad. Even if you have removed the offending default route using the route delete command it can still persist in the AIX ODM. Here’s what you do to fix this:-

First let’s back up the ODM…

cd /etc/objrepos 
cp CuAt cuat.old 
cp CuDep cudep.old 
cp CuDv cudv.old 
cp CuDvDr cudvdr.old 
cp CuVPD cuvpd.old

Now run this to see all the default routes…

odmget -q 'name=inet0' CuAt

Choose the offending route and check the value is correct using (as an example)…

odmget -q 'value=net,-hopcount,0,,0,44.1.128.51' CuAt

If we’re happy you got the right value, delete it with (as an example)…

odmdelete -o CuAt -q 'value=net,-hopcount,0,,0,44.1.128.51'

Now recheck the ODM to see if it’s gone correctly…

odmget -q 'name=inet0' CuAt

Finally run

savebase
bosboot -a

To save things correctly.

This procedure came courtesy of Ross.