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I have a site A which consists of the following IP address and subnets:

  1. 192.168.10.0/24 (internal)
  2. 172.17.0.0/24(DMZ)
  3. BGP tunnel tunnel IP with 172.16.0.1 255.255.255.252
  4. Cloud IP address of 10.0.0.0/8

I would like to do a Site-to-Site VPN from Site B to Site A.

Site B consist of the IP address block: 172.16.0.0/12

My question is:

If I do a Site-to-Site VPN from B to A(DMZ) will it cause any IP conflicts? Or, do I need to do something to prevent 172.16.0.0/12(site B) to go to the 192.168.10.254 router?

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  • At site b, do you use any addresses in the range 172.16.0.0 - 172.16.0.4? – Ron Trunk Jan 5 '18 at 2:53
  • Hi Ron, yes there is one IP with 172.16.0.1 – user3612001 Jan 5 '18 at 7:12
  • You can NAT the local subnet (172.16.0.0/12) at Site B to another subnet when doing VPN tunnel between Sites A and B. – Hung Tran Jan 5 '18 at 9:10
  • 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. – Ron Maupin♦ Apr 1 '18 at 19:25
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Question A: with non-conflicting adresses/networks there will be no problem

Question B: you can set up all routes through the tunnel but on site A you need to make sure that the already present 172.16.0.1/30 has a lower metric/higher priority than the 172.16.0.0/12 to site B. That means that you can't reach B's 172.16.0.1 from site A. Solving this would involve destination NAT which is rather messy.

Making A's 172.16.0.1/30 reachable from site B will also be tricky and messy. Do really need it? Is renumbering an option?

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  • Hi Zac67, Thank for your reply. i wish i could change the IP addresses =( – user3612001 Jan 5 '18 at 8:12
  • Hi, If right now from site B to site A (DMZ)(172.17.0.0/24) network and in the site to site settings i only allow 172.16.0.0/24 to enter my subnet. Will this still cause a IP conflict with BGP tunnel IP address? – user3612001 Feb 2 '18 at 9:15

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