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Community Member

Hub router for VPN

We're replacing a third party router with a Cisco 1721. This location is the hub of multi-location (3 remote sites) VPN.

The 3 remote sites are all on fixed public IPs.

I've seen examples of both no assupmtion/restriction of remote IPs (crypto isakmp key [key] address; as well as setting a key per remote (crypto isakmp key [key1]address [remote ip1]

crypto isakmp key [key2] address [remote ip2]

crypto isakmp key [key3] address [remote ip3]

Is there a disadvantage/security concern to using the quad-0 approach?


Re: Hub router for VPN


AFAIK with the second config option you are clearly mentioning the peers with which your hub router will have ISAKMP key negotiations and exchange.

With the first statement you have your hub to negotiate and exchange keys with any routers in valid ip.

If you are having static ips in the remote sites then better to go with the second option..

first option is clearly used when you have dynamic ips being assigned to the remote clients..


Community Member

Re: Hub router for VPN

There are no advantages or disadvantages other than what should be obvious.

Single key.

Advantage: Simple administration, common config on all routers.

Disadvantage: Potentially allows anyone to connect to the router from the Internet if not forbidden by another policy on the router.

Multiple keys.

Advantage: ISAKMP can not be negotiated if not specifically configured on the router for that remote IP address. Conceptually more secure.

Disadvantage: More administrative overhead.

With 3 sites, the specific key per site is fairly easy to do. If you had 200 sites, that method would be much less doable. You could do a quick estimate. (N * 5) + (N ^ 2) minutes to do your entire network, or something in that line.

It's much easier if you have a system that manages this for larger installs. I believe this is the one of the purposes of Cisco's GET VPN.


Community Member

Re: Hub router for VPN

Thank you all for the responses. We have a (mostly) successful implementation. Traffic passing well from hub to spokes. Working on a few spoke to hub issues.

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