CODEWITHSUNDEEP
linuxgoogle-cloud-platformroutes
lfreez
lfreez

Reputation: 77

Linux VM instance as a Gateway between two different subnets

We have a requirement to create a VPN tunnel between 2 sites. one is my client's on-premise site which using cisco VPN gateway and another site in Google Cloud which managing by our team.

we have 2 subnets in our VPC network 192.168.1.0/24 (this range need reach via the VPN tunnel) and 192.168.10.0/24

VPN tunnel needs to connect the following IP ranges:

Client end: 10.10.0.0/24

Our end: 192.168.1.0/24 (web servers running)

But my client using our Internal Network ranges 192.168.1.0/24 on their side too. so we tried to NAT but unfortunately GCP Cloud NAT Feature cannot use with GCP Cloud VPN.

Considering that I have tested this scenario in my test environments with a new network range (172.10.10.X/24).

Steps followed by me: Created a Linux VM instance as a Gateway which has two network interfaces (one interface(eth0) in 172.10.10.X/24 range and the other interface(eth1) in 192.168.1.0/24)

VPN tunnel created between following IP ranges:

Client end: 10.10.0.0/24

Our end: 172.10.10.X/24

I can ping to 172.10.10.X/24 range from 10.10.0.0/24 but cannot ping to 192.168.1.0/24 from 10.10.0.0/24

Hope I missed something here and need to add routing, can someone guide me with few steps?

Thanks

Upvotes: 1

Views: 472

Answers (1)

Sergiusz
Sergiusz

Reputation: 1245

As Mentioned by @John Hanley in comment, overlapping networks are not supported.
You can only set up static routing in specific scenarios:

Narrower than on-premises IP range (longer subnet mask)

Google Cloud lets you create a custom static route with the 10.2.0.0/16 destination and next hop Cloud VPN tunnel; however, traffic to IP addresses in 10.2.99.0/24 remains inside your VPC network.

The best approach would be to re-address one of the networks.

Upvotes: 1

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