One vendor wanted to install their VPN device (Cisco 800) behind the firewall. They asked us to open ports so they can establish the tunnel.

Another vendor wanted to install their VPN device (Cisco 1921) outside the firewall, but physically attached to our network. They would then be routed into our network through the gateway. (Is this even possible? This is a secondary question that doesn't have to be answered here)

In general, which is more secure?

What are the pro/con of each configuration?

  • 1
    What is the end goal? Are you connecting to equipment hosted by the vendor, is the vendor connecting to your equipment for support, both or something different? Knowing the end goal will help correctly answer the question. Jul 19, 2013 at 18:55
  • Did any answer help you? if so, you should accept the answer so that the question doesn't keep popping up forever, looking for an answer. Alternatively, you could provide and accept your own answer.
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    Aug 8, 2017 at 10:00

1 Answer 1


for an ipsec tunnel i believe you need to allow the following traffic between endpoints.

ip protocol 50 ip protocol 51 udp 500

the second option sounds like their 1921 will have to be in the outside ip space of your firewall. they will terminate their traffic to the 1921 and your layer 3 protocols will take over from there.

  • Regarding the second option (1921), what are the pros/cons of going this route? This looks like what the 3rd party wants to go with, but I don't really understand the risks.
    – John Lee
    Jul 23, 2013 at 17:03
  • I just had a conversation with the vendor, and they think having the router behind the firewall adds security for our network because we can monitor the activity through our firewall. This makes sense. On the other hand, they said having the router outside the firewall makes it more manageable for them so they don't have to go through us if they have to make modifications to the router (which also makes sense). If anyone cares to add more pros/cons, I would appreciate it both for me and others.
    – John Lee
    Jul 23, 2013 at 18:34
  • You have pretty much summed it up. I would prefer to establish a peer relationship with an outside vendor if possible instead of hosting their equipment. With a peer relationship you at least have the ability on your firewall to only allow the necessary specific traffic from the peer for your business purpose. If you host them inside you network you actually open up more concern since you have to be more aware of their maintenance routines.
    – harrijs
    Jul 23, 2013 at 19:31

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