Network layout: Laptop (OpenVPN client) <-> router with 192.168.1.xxx subnet <-> internet <-> Home router (running DD-WRT with OpenVPN server) with 192.168.11.xxx subnet
The VPN server is operating in layer 2 mode (bridge). All of my internet traffic passes through the VPN tunnel. My home router & VPN have an external IP of 68.64.127.82
.
My laptop (VPN client) has an IP address on the physical LAN of 192.168.1.40
. My IP address on the VPN is 192.168.11.50
.
Here is my question: What makes all the internet traffic pass through the VPN tunnel?
Network Destination Netmask Gateway Interface Metric
0.0.0.0 0.0.0.0 192.168.1.1 192.168.1.40 20
0.0.0.0 128.0.0.0 192.168.11.1 192.168.11.50 30
The first line says everything should go the router I'm physically connected to (not the VPN router). The second line makes no sense to me. The 192.168.11.xxx
subnet is on my VPN. How can you have a 0.0.0.0
destination with a netmask?!?
Question 2: What does the 128.0.0.0
netmask mean with a 0.0.0.0
destination?
Question 3: Why does the second line take priority over the first line?
Thanks for your help!
Here is my full routing table:
Here is my full routing table:
C:\Users\owner>route print
===========================================================================
Interface List
19...00 ff 79 ee e1 6b ......TAP-Windows Adapter V9
10...00 1a 4b 13 d2 92 ......Broadcom NetLink (TM) Gigabit Ethernet
1...........................Software Loopback Interface 1
===========================================================================
IPv4 Route Table
===========================================================================
Active Routes:
Network Destination Netmask Gateway Interface Metric
0.0.0.0 0.0.0.0 192.168.1.1 192.168.1.40 20
0.0.0.0 128.0.0.0 192.168.11.1 192.168.11.50 30
68.64.127.82 255.255.255.255 192.168.1.1 192.168.1.40 20
127.0.0.0 255.0.0.0 On-link 127.0.0.1 306
127.0.0.1 255.255.255.255 On-link 127.0.0.1 306
127.255.255.255 255.255.255.255 On-link 127.0.0.1 306
128.0.0.0 128.0.0.0 192.168.11.1 192.168.11.50 30
192.168.1.0 255.255.255.0 On-link 192.168.1.40 276
192.168.1.40 255.255.255.255 On-link 192.168.1.40 276
192.168.1.255 255.255.255.255 On-link 192.168.1.40 276
192.168.11.0 255.255.255.0 On-link 192.168.11.50 286
192.168.11.50 255.255.255.255 On-link 192.168.11.50 286
192.168.11.255 255.255.255.255 On-link 192.168.11.50 286
224.0.0.0 240.0.0.0 On-link 127.0.0.1 306
224.0.0.0 240.0.0.0 On-link 192.168.1.40 276
224.0.0.0 240.0.0.0 On-link 192.168.11.50 286
255.255.255.255 255.255.255.255 On-link 127.0.0.1 306
255.255.255.255 255.255.255.255 On-link 192.168.1.40 276
255.255.255.255 255.255.255.255 On-link 192.168.11.50 286
===========================================================================
Here is my ipconfig:
Windows IP Configuration
Ethernet adapter Local Area Connection 2:
Connection-specific DNS Suffix . :
Description . . . . . . . . . . . : TAP-Windows Adapter V9
Physical Address. . . . . . . . . : 00-FF-79-EE-E1-6B
DHCP Enabled. . . . . . . . . . . : Yes
Autoconfiguration Enabled . . . . : Yes
Link-local IPv6 Address . . . . . : fe80::c1f8:5d3:e14:dba6%19(Preferred)
IPv4 Address. . . . . . . . . . . : 192.168.11.50(Preferred)
Subnet Mask . . . . . . . . . . . : 255.255.255.0
Lease Obtained. . . . . . . . . . : Thursday, December 11, 2014 11:20:53 AM
Lease Expires . . . . . . . . . . : Friday, December 11, 2015 11:20:53 AM
Default Gateway . . . . . . . . . :
DHCP Server . . . . . . . . . . . : 192.168.11.0
DHCPv6 IAID . . . . . . . . . . . : 520159097
DHCPv6 Client DUID. . . . . . . . : 00-01-00-01-16-A1-5A-F6-00-1A-4B-6B-D2-7C
DNS Servers . . . . . . . . . . . : fec0:0:0:ffff::1%1
fec0:0:0:ffff::2%1
fec0:0:0:ffff::3%1
NetBIOS over Tcpip. . . . . . . . : Enabled
Ethernet adapter Local Area Connection:
Connection-specific DNS Suffix . :
Description . . . . . . . . . . . : Broadcom NetLink (TM) Gigabit Ethernet
Physical Address. . . . . . . . . : 00-1A-4B-13-D2-92
DHCP Enabled. . . . . . . . . . . : Yes
Autoconfiguration Enabled . . . . : Yes
Link-local IPv6 Address . . . . . : fe80::61c0:c604:f3e5:498%10(Preferred)
IPv4 Address. . . . . . . . . . . : 192.168.1.40(Preferred)
Subnet Mask . . . . . . . . . . . : 255.255.255.0
Lease Obtained. . . . . . . . . . : Thursday, December 11, 2014 11:20:35 AM
Lease Expires . . . . . . . . . . : Friday, December 12, 2014 11:20:35 AM
Default Gateway . . . . . . . . . : 192.168.1.1
DHCP Server . . . . . . . . . . . : 192.168.1.1
DHCPv6 IAID . . . . . . . . . . . : 234887755
DHCPv6 Client DUID. . . . . . . . : 00-01-00-01-16-A1-5A-F6-00-1A-4B-13-D2-92
DNS Servers . . . . . . . . . . . : 192.168.1.1
NetBIOS over Tcpip. . . . . . . . : Enabled
Best Answer
Solved! Thanks to eibgrad at the DD-WRT forums. Here is his answer:
(Source: http://www.dd-wrt.com/phpBB2/viewtopic.php?t=277001 )
It's just a clever hack/trick.
There’s actually TWO important extra routes the VPN adds:
The reason this works is because when it comes to routing, a more specific route is always preferred over a more general route. And
0.0.0.0/0.0.0.0
(the default gateway) is as general as it gets. But if we insert the above two routes, the fact they are more specific means one of them will always be chosen before0.0.0.0/0.0.0.0
since those two routes still cover the entire IP spectrum (0.0.0.0
thru255.255.255.255
).VPNs do this to avoid messing w/ existing routes. They don’t need to delete anything that was already there, or even examine the routing table. They just add their own routes when the VPN comes up, and remove them when the VPN is shutdown. Simple.