## SLIP over IP using VSPDL This example is meant to show how stable and versatile the VSPDL currently is. It is not to be taken literally, for real-world use, but more as a demonstration. Test it, understand VSDL's capabilities, and go do something creative with VSPDL. We will be setting up a VPN of sorts, using [SLIP](http://en.wikipedia.org/wiki/Serial_Line_Internet_Protocol). This is particularly useful for testing VSPDL in kernel interdriver communication. Let's say we have two PCs. PC #1 is at IP address 11.11.11.11, while PC #2 is at 22.22.22.22. First, install and test VSPDL on both machines. ### Configuration #### Client Now, let's configure PC #1's VSPDL as the TCP client. The following snippet comes from the section of the VSPDL configuration file (/usr/local/vspd/etc/vspd.conf) for PC #1:

#### Server Let's make PC #2's VSPDL into the TCP server. Here's what the same snippet should look like on PC #2:

**Note**: You can use server/client connection mode too, but TCP as transport is preffered #### Establishing The Link Restart the VSPDaemons on both PCs:

# service vspd restart

Open a SLIP connection on PC #1:

# /sbin/slattach -p slip -s 115200 /dev/vsps0 & # /sbin/ifconfig sl0 10.0.0.1 pointopoint 10.0.0.2

Now a SLIP connection on PC#2: # /sbin/slattach -p slip -s 115200 /dev/vsps0 & # /sbin/ifconfig sl0 10.0.0.2 pointopoint 10.0.0.1 10.0.0.x is our new internal SLIP VPN IP range. #### Testing Let's check that our new interfaces are there on PC #1:

# ifconfig sl0 sl0 Link encap:Serial IP HWaddr .... inet addr:10.0.0.1 P-t-p: 10.0.0.2 ...

And on PC #2:

# ifconfig sl0 sl0 Link encap:Serial IP HWaddr .... inet addr:10.0.0.2 P-t-p: 10.0.0.1 ...

Now let's ping. First from PC #1:

# ping -I sl0 10.0.0.2 PING 10.0.0.2 (10.0.0.2) 56(84) bytes of data. 64 bytes from 10.0.0.2: icmp_seq=1 ttl=64 time=0.045 ms

And then from PC #2:

# ping -I sl0 10.0.0.1 PING 10.0.0.1 (10.0.0.1) 56(84) bytes of data. 64 bytes from 10.0.0.2: icmp_seq=1 ttl=64 time=0.045 ms

as you see, I'm pinging using ”-I sl0” PING option. you can add such a rule into your routing rules to use it by default for your virtual serial VPN network on both machines:

# route add -net 10.0.0.0 -mask 255.255.255.0 sl0

**Tip**: If something goes wrong, look at /usr/local/vspd/var/dev.0.log to see if the VSPDLs are connected to each other or not.