Packet filtering

Can a firewall on a different network filter packets based on private IP addresses from a different network it's not connected to?
E.g Company A has an internet facing firewall, from this firewall can they filters packets coming from Company B's private IP range?

Someone told me that the above is possible but the explanation it didn't make sense, what happens if you only want to block Company B but Company C is using the same internal range? From my limited understanding you can only do this for Public IP ranges or ranges from networks which you are connected to.

Thanks

Find more posts tagged with

SAVE $250 on Your Boot Camp — Use Code "EXAM26"

Exclusively for TechExams members for Infosec Boot Camps starting before April 30, 2026

View Boot Camps

Comments

networker050184

Depends on the set up really, but most likely not. Are there tunnels/VPNs involved? Where in the flow of traffic is the firewall?

atorven

No VPNs/Tunnels involved.

networker050184

There are some applications that may have the original IP embedded and can be filtered on with custom filtering. Other than that, I don't know of anyway to do the sort of thing you are asking about and I would assume you are correct about overlapping private IPs causing trouble.

ptilsen

networker050184 wrote: »

There are some applications that may have the original IP embedded and can be filtered on with custom filtering.

This is the only thing I can think of as well. For example, one of the voice programs (Ventrilo or TeamSpeak -- I forget) uses your private IP for servers hosted on the Internet.