Company A owns a building and leases out 2 offices to other companies.

Telecom 1 provides internet to Router 1 with ip address x.x.x.121

Company A connects their router, Router A, to it and gives it IP address x.x.x.122
Company B connects their router, Router B, to it and gives it IP address x.x.x.123
Company C connects their router, Router C, to it and gives it IP address x.x.x.124

Is that effectively the same as each company having a seperate line?

Assume that A has control of the main router and each has access to their own router but no one else's.

EDIT: In my case the main router is a Cisco 2811
Company A is using a Ubiquiti EdgeMax
Company B unsure
Company C a BT home hub

  • 1
    Are these all the same types of routers?
    – user
    Jan 13, 2020 at 13:46

1 Answer 1


Since they use different routers (telecom + companies), it would be more secure to have them behind another router. An attacker would need to attack the telecom router and then the company routers, instead of just the company routers.

Additionally, if the telecom router has client isolation capabilities enabled, then the companies would have to attack the telecom router before attacking the other company routers.

One possible drawback with having them behind the telecom router is if they're able to attack each other, then they may have more bandwidth available with which to launch attacks.

  • 1
    Could you give any information about "internal" security. Say one of the companies attempting to access the others networks?
    – Sam Dean
    Jan 13, 2020 at 13:56
  • 1
    @SamDean Companies attacking each other would be in a similar situation both behind the router and directly connected to Internet (company A could attack company B's router directly unless the telecom router has client isolation). If they were all on the Internet then they could attack each other anyways.
    – user
    Jan 13, 2020 at 13:58

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