What is/are your way(s) to block the target from accessing your servers?

Question

Hello,

I am looking for "the best way" to block an Ip address from the internet to access my servers.

One funny man just tells me to

1. create a loopback interface on Fortigate

2. create an object group, enable the "Static route configuration", and add those BlackList IP addresses to that object group

3. Add a static route, Dst set to the object group, Route interface: The loopback one

So, the "return traffic" is eliminated.

Well, I then find a KB from Fortinet and just have a Firewall policy with "match-vip enable" to block the target.

Technical Tip: Firewall does not block incoming (W... - Fortinet Community

So, what is/are the difference(s) between both methods?

And, are there even benefits if we are using the Funny guy's solution? Like CPU loading / Memory loading ... anything is better than the match-vip.

tio3udes · Answer

Hello Mr Potato.

The funny man is not wrong, this is a way to block the traffic, but you became vulnerable to a DoS situation, because the traffic routed to the loopback or blackhole would still appear on your session table until the ttl expires.

The best way is to create a blacklist policy with the "match-vip enable" parameter. This way traffic is actually blocked by the firewall policy. The match vip is necessary in order to the top-down order of policy check to be respected even when it comes to vip objects.

the loopback/blackhole solution works, but can lead to a conserve mode/DoS situation due to the session table size. This is normally done on routers.

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