vCloud Console shows as disconnected

The Story: I needed to change the secondary DNS settings in the vCloud Director 5.1 virtual machine (Red hat 6.2). A network service restart was required for the settings to take effect. After this I noticed that the vCloud consoles would not connect and would indicate disconnected and only show a black screen. This was a problem in the production environment so I needed to find the problem. I had seen something similar to this the last time the vCloud Director VM was restarted but it was done on a weekend and when I tried to look for the cause of the problem (3 hours later) the problem had disappeared. This time I had no VM consoles at 7am in the morning.

I found that I could not ping the console proxy nic IP address from the production network or from the firewall or from the core switch where the default gateway for the vCloud Director VM was configured. I could ping it from VMs on the same network as the vCD VM and the consoles opened correctly on these VMs too. Seemed to me that the console proxy network had lost its default gateway but after looking at the Redhat configuration files it was configured correctly.

The solution: Started looking for Redhat problems with dual networks and found the following

https://access.redhat.com/site/solutions/53031

This looked very similar to my problem so I applied the following changes to redhat:

I modified the following file

/etc/sysctl.conf

Changed the following setting:

net.ipv4.conf.default.rp_filter = 2

 Restarted the vCloud Director virtual machine.

Problem fixed. Ping from all networks is successful and vCloud console is working again.