How to push the routing table to the client?

[hack3rcon]

Hello,
I have two VMs in VirtualBox and selected the NAT Network type for their networking.
For both VMs, I configured the network manually. On Server (Debian) my network configuration is:

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enp0s3: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        inet 10.0.2.15  netmask 255.255.255.0  broadcast 10.0.2.255
        inet6 fe80::a00:27ff:feed:b47c  prefixlen 64  scopeid 0x20<link>
        ether 08:00:27:ed:b4:7c  txqueuelen 1000  (Ethernet)
        RX packets 46567  bytes 21273157 (20.2 MiB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 38209  bytes 7396310 (7.0 MiB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

And routing table is:

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# route -n
Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
0.0.0.0         10.0.2.2        0.0.0.0         UG    0      0        0 enp0s3
10.0.0.0        0.0.0.0         255.0.0.0       U     0      0        0 enp0s3
10.0.2.0        0.0.0.0         255.255.255.0   U     0      0        0 enp0s3

I can ping Internal and external networks:

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# ping google.com
PING google.com (216.239.38.120) 56(84) bytes of data.
64 bytes from any-in-2678.1e100.net (216.239.38.120): icmp_seq=1 ttl=50 time=25.3 ms
64 bytes from any-in-2678.1e100.net (216.239.38.120): icmp_seq=2 ttl=50 time=27.1 ms
64 bytes from any-in-2678.1e100.net (216.239.38.120): icmp_seq=3 ttl=50 time=27.8 ms
^C
--- google.com ping statistics ---
3 packets transmitted, 3 received, 0% packet loss, time 2032ms
rtt min/avg/max/mdev = 25.315/26.722/27.752/1.030 ms
#
# ping 172.20.1.2
PING 172.20.1.2 (172.20.1.2) 56(84) bytes of data.
64 bytes from 172.20.1.2: icmp_seq=1 ttl=125 time=1.54 ms
64 bytes from 172.20.1.2: icmp_seq=2 ttl=125 time=1.37 ms
64 bytes from 172.20.1.2: icmp_seq=3 ttl=125 time=2.87 ms
^C
--- 172.20.1.2 ping statistics ---
3 packets transmitted, 3 received, 0% packet loss, time 2051ms
rtt min/avg/max/mdev = 1.366/1.922/2.867/0.671 ms

On client (Windows OS), I used the below configuration:

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IP: 10.0.2.16
Subnet Mask: 255.255.255.0
Default Gateway: 10.0.2.15         ==> Linux IP address

Both server and client can see each other. When the client connects to the server, I want the default gateway of server to be set on the client.

Server.conf:

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push "redirect-gateway def1 bypass-dhcp"
push "route 10.0.2.0 255.255.255.0 10.0.2.2 1"
push "dhcp-option DNS 1.1.1.1"

Client.ovpn:

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route 10.0.2.0 255.255.255.0 10.0.2.2

I connected to the server, but default gateway not set:

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Unknown adapter OpenVPN TAP-Windows6:

   Connection-specific DNS Suffix  . :
   Link-local IPv6 Address . . . . . : fe80::b404:5a8b:df0e:52c3%15
   IPv4 Address. . . . . . . . . . . : 10.8.0.6
   Subnet Mask . . . . . . . . . . . : 255.255.255.252
   Default Gateway . . . . . . . . . :

Why?

Thank you.

[ordex]

Because when using "def1" (it's the right thing to do), OpenVPN will install two routes, namely 128.0.0.0/1 and 0.0.0.0/1), and won't touch the default gateway. (The manpage explains these approach a bit better)

Therefore, even if the default gateway hasn't changed, you should still see traffic entering the VPN interface.

[hack3rcon]

Because when using "def1" (it's the right thing to do), OpenVPN will install two routes, namely 128.0.0.0/1 and 0.0.0.0/1), and won't touch the default gateway. (The manpage explains these approach a bit better)

Therefore, even if the default gateway hasn't changed, you should still see traffic entering the VPN interface.

Hello,
Thank you so much for your reply.
Is there a command to change the default gateway?

[ordex]

I think you can just remove the "def1" from the "redirect-gateway" directive, but why?

[hack3rcon]

I think you can just remove the "def1" from the "redirect-gateway" directive, but why?

Hello,
Thanks again.
So, push "redirect-gateway bypass-dhcp" changes the default gateway?

[Pippin]

Hi,

Why not answer the question?

I think you can just remove the "def1" from the "redirect-gateway" directive, but why?

[hack3rcon]

Hi,

Why not answer the question?

I think you can just remove the "def1" from the "redirect-gateway" directive, but why?

Hello,
Thank you so much for your reply.
I just wanted to know it. Can set the default gateway cause interference?