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ASA 5505 site to site VPN static route how to or possible workarounds

Posted on 2009-07-08
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Last Modified: 2012-05-07
Currently I have a site to site VPN setup between 2 ASA 5505's.  The local subnets are 192.168.1.0/24 for the main location and 192.168.2.0/24 for the remote location.  The last part of this equation is a vendor router(192.168.2.25) is located on remote subnet with a connection to a 10.0.0.0/24 network.

A server at the main location has an IP address of 192.168.1.20 and it will need to talk to the vendor router(192.168.2.25) in order to reach the 10.0.0.0/24 network.

How can I get 192.168.1.20 to communicate to the 10.0.0.0/24 network utilizing the VPN connection to get to 192.168.2.25?

Both ASAs are running 7.2

I know the ASA is cable of some some static routing - is it possible to have a static route traverse the VPN to the 192.168.2.25 router?  What configurations will I need to add to make this work?

If not, what possible workarounds are available to accomplish this easily?  Thanks.

Ideally I would have a static route for 10.0.0.0 255.255.255.0 via 192.168.2.25, but this does not appear to be an option with the ASA.  
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Question by:salesandservice
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by:salesandservice
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Is it possible to do this without changing the default gateway of the server (currently set to the ASA at the main location)?
 http://www.cisco.com/en/US/products/ps6120/products_tech_note09186a0080734db7.shtml
It seems possible to change the default gateway to a different router and configure that router to point 10.0.0.0/24 traffic to 192.168.2.25 and that way the ASA would only need to send traffic over to the remote subnet via VPN as it normally does.  Would this work or am I missing something?
Any other configurations/ideas? Thanks
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by:salesandservice
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The "same-security-traffic permit intra-interface " seems to indicate a similar setup to above except I could leave the default gateway as is.
So traffic going from the server at the main location to the 10.0.0.0/24 network would go to the pix and then go to the new router with an address of lets say  192.168.1.5.
So config would be changed to:
same-security-traffic permit intra-interface
route inside 10.0.0.0 255.255.255.0 192.168.1.5(new router)
-----
And then traffic would go to the router with a config of:
10.0.0.0 255.255.255.0 192.168.2.25
And traffic would travel over the VPN tunnel and out thru the Vendor router - will this configuration work?
 
 
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Boilermaker85 earned 500 total points
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First, can I assume the ASA at the main location is also your Internet gateway for users at main? If you don't have a conflicting 10.0.0.0/24 network on your main site, and your default gateway leads you to this Internet gateway/VPN Firewall, then all you need to do is make sure that the 10.0.0.0 network is in your Crypto ACL and natural routing will get it across. Of course you still need the traffic acls at both end to allow the traffic. And at the remote ASA a static route statement:
Main ASA:
access-list VPN-Site2 permit ip 192.168.1.0 255.255.255.0 192.168.2.0 255.255.255.0
access-list VPN-Site2 permit ip 192.168.1.0 255.255.255.0 10.0.0.0 255.255.255.0
crypto map mymap  11 match address VPN-Site2

Remote ASA:
route inside 10.0.0.0 255.255.255.0 192.168.2.25


If your VPN ASA is not the same as your Internet ASA at the main site, then at your core router at main site, you will need to have a static route (ip route 10.0.0.0 255.255.255.0 192.168.1.x) to tell your own network that the 10 network is reachable cia. the VPN ASA.
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by:salesandservice
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would it be possible to set the default gateway of the server at the main location to point to the router at the remote location(Internet access will not be required for this server only access is needed to the vendor router).  
I would think the same crypto ACLs would need to be applied.
Is this a viable alternative?  What are implications of doing this?
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by:Boilermaker85
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No. Your main location server cannot arp for the Mac of the remote router with the VPN in between.  A default gateway must have an address on the same subnet you are on, so that layer 2 arp can occur.
The implications of doing what you suggested are that you won't be able to bring up VPN.
The solution I gave is the only one I know will work. Why do you need an alternative?
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by:salesandservice
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As you mentioned earlier, the VPN ASA is also the internet connection at the mainsite.  

When the server goes to send data to the 10.0.0.0 network, how is this traffic able to go over the VPN tunnel to the remote site instead of being sent out to the outside interface(internet) via the default route on the ASA?
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by:Boilermaker85
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access-list VPN-Site2 permit ip 192.168.1.0 255.255.255.0 192.168.2.0 255.255.255.0
access-list VPN-Site2 permit ip 192.168.1.0 255.255.255.0 10.0.0.0 255.255.255.0
crypto map mymap 11 match address VPN-Site2
of course there are other crypto and isakmp statements for the VPN. I assume you can finish that on your own. The point is the ACL association to the crypto map.

The above tells the ASA that traffic to 10.0.0.0/24 is interesting traffic for encryption on a particular tunnel. THe ASA just encrypts it and passes it across the tunnel where it is decrypted, and then routed on its way. That remote ASA has the static route that tells the packet the next hop is through the inside Interface via the router.
 
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by:salesandservice
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Thank you for the assistance.  This worked great and I appreciate the follow-up to the related questions.
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