Are you using the DHCP.
Ive encountered this problem and was the bug: DHCP CONFIGURATION CAUSING ROOT.SH FAIL[Bug ID 14638061]
And, maybe useful for you this note: Troubleshooting 11.2 Grid Infrastructure root.sh Issues (Doc ID 1053970.1)
Try this. It worked for me.
Please keep in mind that you will need wait till each step finishes successfully before move to next one
For Step1 and 2, you can skip node(s) on which you didn't execute root.sh yet.
Step 1: As root, run "$GRID_HOME/crs/install/rootcrs.pl -verbose -deconfig -force" on all nodes, except the last one.
Step 2: As root, run "$GRID_HOME/crs/install/rootcrs.pl -verbose -deconfig -force -lastnode" on last node. This command will zero out OCR and VD disk also.
Step 3: As root, run $GRID_HOME/root.sh on all node one by one