how do two servers communicate when there is firewall?

Question

how do two servers communicate when there is firewall?

Answer 1

Do you have servers that are redundant but separated by a firewall and therefore can't update each other? (I can't think of very many reasons why servers need to communicate with each other).



First you have to figure out what protocol they use to communicate and then, assuming it's IP based, as stated above, open those ports to those specific IP addresses on the firewall. If it's layer 2 based you may have to get creative and possibly try a PPTP or GRE tunnel.

Answer 2

Hello Mabin;;



Firewalls have ports that open when instructed or have permission.



Quick example; Anti virus software needs that permission to use a port to check for updates on their servers. Windows also needs permission to go to their servers for the same reason. Setting up firewalls is a matter of Servers being allowed to open or use a port to communicate with another server or computers. It is a mater of how the firewall is configured to allow or permit this communication.



Here is a bad example. New printer with software on disk installed and must have been complacent or just over looked when asked if I wanted to have the software check for upgrades periodically. As a result of overlooking this was ENABLED. One day noticed the hard drive working when should not have and using the task manager found a file called "sphook.exe" using resources. Searched and found it was a tracking file. Removed it and checked the firewall settings to notice that the HP software was ALLOWED and nothing else was out of the ordinary. Immediately changed the setting to disable.



Firewalls have ports to open only with permission. E-mails go thru many servers at times before they get to you because you give the firewall permission (Enabled) to receive and send with that software enabled.



Checking firewall settings often is a good habit. Using a server at home would require configuration in the same manner.



Have fun



tom

Answer 3

If both servers are within the same LAN or local network (connected to the same switch or router) then some Firewalls allow internal traffic on the same subnet without issues.

Anotherwards, they simply communicate and the Firewall stays out of their way.



However, when the 2 servers are in different subnets OR one of them is being accessed over the Internet (WAN) THEN special rules must be setup on the firewall which allows that traffic to go through.



Some examples of a firewall rule would be:



Allow ALL access to a specific destination IP such as 10.160.21.132

OR

Allow all traffic only on ports 7412-7415



Firewall rules can also restrict which protocols are used, such as UDP or TCP as well as enforce timestamps, such as: ALLOW between 8:00AM to 5:00PM but not 5:01PM-7:59AM



Firewalls can also have different inbound and outbound rules. Meaning that it can allow 1 server to communicate with another one (outbound) But Deny access from the external server trying to reply back (inbound)





Windows XP SP2 or later had built into it a very basic Inbound firewall only. It only blocked things externally from coming into the computer. It didn't care what was sent out from the computer.



Windows 7 has a more advanced inbound/outbound firewall which can protect both what is coming in as well as going out of the computer.





Home firewalls on most Routers have only very basic Firewall rules. Usually port rules, time rules and protocol rules.

For a computer over the internet to access your home computer, you often times need to enable "Port forwarding" which forwards any traffic on a specific port to a specific computer at your house which can respond to those requests.

Answer 4

There should be a rule in the fire wall to allow connections from the each server to go to each other.