If a firewall is configured with different VLANs, how could an attacker perform an attack over a different VLAN. I see a lot of information on scanning, exploiting, and other attacking methods using a device's IP address. Most of this information is assuming the attacker is on the same VLAN as the target (for simplicity sake).

For example, I am the attacker and my IP address is My target's IP address is I want to run an exploit against my target, yet I can't even ping the target (Destination Host Unreachable).

I understand this is because the firewall on the network divides up the network into virtual LANs and everything routed is through the firewall. Therefor, if one device tries talking to a different device on a separate VLAN, the router says "I don't know what you're talking about" (correct me if I'm wrong here).

Is it possible to attack a target from a different VLAN, and if so, what are some methods used? I am having a hard time figuring out different attacking methods when a simple ping reports an unreachable destination.

1 Answer 1


If the firewall which defines the VLANs is configured not to allow traffic between the VLANs then the answer is that you can't unless the firewall is in some way misconfigured. That's part of the reason for having VLANs in the first place.

However routes may exist for some specific traffic from VLAN to VLAN, or between devices on different VLANs, but they need to be configured as such in the firewall.

From personal experience I've seen TCP traffic controlled between VLANs but not UDP, and also ICMP sometimes allowed between, but this is due to the firewall config.

This is not the same as possible ARP flooding switches to force a switch to revert to a broadcast hub to gain access to different areas of a switched LAN, firewalls don't (shouldn't) downgrade this way when under extreme stress. However, it's worth checking whether any vulnerabilities for the VLAN managing firewall exist that can be exploited to overcome VPAN separation controls.

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