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MenInTheMiddle
Asked: 2021-01-29 15:53:57 +0800 CST

Multiple subnets through VPN openvpn

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I'm facing the following problem and after a huge amount of trial and errors i could use ask for some help.

Situation: Scheme

SiteA have LAN network: 192.168.101.0/24 while SiteB have LAN network 192.168.102.0/24. But on a Layer2 switch on SiteB there is an IP device with static ip 192.168.254.2/24.

SiteA and SiteB are connected with a Site To Site openVPN and from SiteA I reach every 192.168.102.0/24 device and vice versa but I don't reach 192.168.254.2.

I created an IP Alias on LAN in SiteB with address 192.168.254.177 then from router on siteB I reach 192.168.254.2 at layer2, but from SiteA I don't reach the 192.168.254.2 device. How can I reach 192.168.254.2 from siteA?

I made a scheme (image above) the hope that it will help.

This is a tcp dump on SiteB Router:

root@Teltonika-RUT240:~# tcpdump -eni any icmp
listening on any, link-type LINUX_SLL (Linux cooked), capture size 262144 bytes
01:04:29.992742  In ethertype IPv4 (0x0800), length 100: 10.168.101.2 > 192.168.254.2: ICMP echo request, id 54537, seq 0, length 64
01:04:29.993001 Out 00:1e:42:2b:12:58 ethertype IPv4 (0x0800), length 100: 10.168.101.2 > 192.168.254.2: ICMP echo request, id 54537, seq 0, length 64
01:04:29.993037 Out 00:1e:42:2b:12:58 ethertype IPv4 (0x0800), length 100: 10.168.101.2 > 192.168.254.2: ICMP echo request, id 54537, seq 0, length 64

10.168.101.2/24 is the SiteB ip on VPN subnet, the openvpn server has ip 10.168.101.1. 00:1e:42:2b:12:58 is the mac address of physical interface on RUT240 SiteB

The siteB router receives the packet icmp from siteA but is doesnt forward it correctly to 192.168.254.2 device!

openvpn subnet

0 Answers