Perform PSConfig upgrade

Hi guys,<o:p></o:p>

I have a client and they have a single farm (SP2010 foundation) with 3 tier. I have two WFE servers and one of them is located on DMZ. It seemed like that for the WFE on the DMZ previously the update binary installed but they forgot to run psconfig for that server.  Last time this farm was updated back in 3 years ago.<o:p></o:p>

I am slightly concern to run  PSConfig.exe? do I have to do that? The farm seems like working as normal only the CA on the WFE (on the DMZ) is not responding...

If I run PSConfig.exe do I have to repeat that for all servers in the farm? Or just run that on the flagged server by Health Analyzer report?<o:p></o:p>

Any advice greatly appreciated.<o:p></o:p>

Thanks<o:p></o:p>

B <o:p></o:p>