OUI-35000: Fatal cluster error encountered while adding a node.

PROBLEM:
OU1-35000: Fatal cluster error encountered ().
Correct the problem and try the operation again.

Solution:

Occurs during installation or adding a node in RAC environment.
Make sure the private node name or virtual hostnames are reachable. If they are not reachable, make sure they exist in DNS or /etc/hosts file.

Due to non availability or communication with clusterware. or wrong entry of host name, public IP, private IP or Virtual IP address during installation.
action: stop and start the CRS in all nodes. or correct the host IP Address.

[root@rac1 bin]# ./crs_stat -t

Name           Type           Target    State     Host
------------------------------------------------------------
ora.demo.db    application    ONLINE    UNKNOWN   rac3
ora....o1.inst application    ONLINE    OFFLINE
ora....o2.inst application    ONLINE    OFFLINE
ora....osrv.cs application    ONLINE    UNKNOWN   rac1
ora....mo1.srv application    ONLINE    UNKNOWN   rac3
ora....mo2.srv application    ONLINE    UNKNOWN   rac1
ora....SM2.asm application    ONLINE    UNKNOWN   rac1
ora....C1.lsnr application    ONLINE    UNKNOWN   rac1
ora.rac1.gsd   application    ONLINE    UNKNOWN   rac1
ora.rac1.ons   application    ONLINE    UNKNOWN   rac1
ora.rac1.vip   application    ONLINE    ONLINE    rac1
ora....SM1.asm application    ONLINE    UNKNOWN   rac3
ora....C3.lsnr application    ONLINE    UNKNOWN   rac3
ora.rac3.gsd   application    ONLINE    UNKNOWN   rac3
ora.rac3.ons   application    ONLINE    UNKNOWN   rac3
ora.rac3.vip   application    ONLINE    ONLINE    rac3

[root@rac1 bin]# ./crsctl stop crs

Stopping resources.
Successfully stopped CRS resources
Stopping CSSD.
Shutting down CSS daemon.
Shutdown request successfully issued.

[root@rac3 bin]# ./crsctl stop crs

Stopping resources.
Successfully stopped CRS resources
Stopping CSSD.
Shutting down CSS daemon.
Shutdown request successfully issued.

[root@rac1 bin]# ./crsctl start crs

Attempting to start CRS stack
The CRS stack will be started shortly

[root@rac3 bin]# ./crsctl start crs

Attempting to start CRS stack
The CRS stack will be started shortly

[root@rac3 bin]# ./crs_stat -t

Name           Type           Target    State     Host
------------------------------------------------------------
ora.demo.db    application    ONLINE    ONLINE    rac3
ora....o1.inst application    ONLINE    ONLINE    rac3
ora....o2.inst application    ONLINE    ONLINE    rac1
ora....osrv.cs application    ONLINE    ONLINE    rac1
ora....mo1.srv application    ONLINE    ONLINE    rac3
ora....mo2.srv application    ONLINE    ONLINE    rac1
ora....SM2.asm application    ONLINE    ONLINE    rac1
ora....C1.lsnr application    ONLINE    ONLINE    rac1
ora.rac1.gsd   application    ONLINE    ONLINE    rac1
ora.rac1.ons   application    ONLINE    ONLINE    rac1
ora.rac1.vip   application    ONLINE    ONLINE    rac1
ora....SM1.asm application    ONLINE    ONLINE    rac3
ora....C3.lsnr application    ONLINE    ONLINE    rac3
ora.rac3.gsd   application    ONLINE    ONLINE    rac3
ora.rac3.ons   application    ONLINE    ONLINE    rac3
ora.rac3.vip   application    ONLINE    ONLINE    rac3


Due to entering wrong IP address also OU1-35000 Fatal error occurs:
figure 1: mismatching of ip addresses

correcting the ip address: after correcting the ip address , no fatal cluster error occurs, lets try  as show in below figure.

hope, it will helps you. 
regards,
Rajeshkumar.