LAN

Name

LAN -- LAN Interfacing.

Description

There are TWO ways for XRPi to interface with the LAN / WiFi. Which one you choose depends on what facilities you need.

The "basic" method accesses the LAN via the Linux kernal.
This mode supports servers, AXIP, AXUDP, AXTCP, IPIP, IPUDP, Telnet, PING, TraceRoute etc.
It does NOT support direct IP routing between XRPi ports and the LAN.
For example, it wouldn't be able to route "raw" IP from a PPP port or RF network onto the LAN (and vice versa).
But it CAN route encapsulated traffic to and from the LAN. For example, you could receive IP over the radio, or over AXIP/AXUDP/IPIP/IPUDP/PPP/SLIP etc, and route it out via the LAN to another node, providing it is encapsulated in IPIP, IPENCAP, IPUDP, IP-over-AXUDP, IP-over-AXIP, IP-over-AXTCP etc.
Using basic mode, it is not possible (yet) to "trace" the Linux kernal TCP/IP activity. Only encapsulated traffic and non-LAN traffic can be traced.
Basic mode does not need an INTERFACE or PORT. All it needs is a "type k" (kernal) default route in IPROUTE.SYS like this:
```
	ip route default  0  *  k
```
In this mode, all servers and LAN traffic in and out of XRPi use Linux's LAN IP address.
The "regular" method for acessing the LAN bypasses the Linux kernal, talking to the hardware in a more direct way.
This mode gives XRPi its own LAN address and IP stack, independent of the Linux one.
It supports all the above modes, PLUS it supports direct IP routing between XRPi ports and the LAN. All LAN traffic to and from XRPi can be "traced".
Regular mode uses an EXTERNAL interface, to which a PORT is attached. They are declared as follows:
```
	INTERFACE=3
		TYPE=EXTERNAL        ; External device driver
		ID=eth0              ; Device to use
		PROTOCOL=ETHER       ; Protocol
		MTU=1064             ; Largest packet size
	ENDINTERFACE
```
The "ID=" directive tells XRPi which Ethernet adaptor to use. This is normally "eth0". If you use an invalid device name, e.g. "eth1", XRPi will start, but will not be able to use Ethernet.
Device "eth0" is usally the Ethernet adaptor and wlan0 is usually the WiFi adaptor. However, the WiFi may appear as "eth1".
The only PROTOCOL accepted at present is ETHER.
The corresponding Ethernet PORT is declared like this:
```
           PORT=1                  ; Port number
        	ID=Ethernet            ; Description
        	INTERFACENUM=3         ; Interface to use
        	IPADDRESS=192.168.0.2  ; Ethernet IP address
        	NETMASK=255.255.255.0  ; Network mask
        	etc...
```
INTERFACENUM must refer to the number of the INTERFACE previously defined.
The port number is not important. It is merely a "handle" for users of the port. It doesn't have to match the INTERFACE number.
IPADDRESS specifies XRPi's IP address, overriding the global IP address only on that port.
Make sure you choose a different IP address to any that Linux is using!
You will also need to set up some LAN IP routing in IPROUTE.SYS, for example:
```
	# Default route via gateway 192.168.0.100 on port 1:
	ip route default  1  192.168.0.100  d
	#
	# Local subnet is routed direct on port 1:
	ip route add 192.168.0.0/24	  *  1  d
```

Caveats

If XRPi is run as a root user, no special conditions apply.

If not run as root, its access to resources is restricted by Linux's security policies.

When running as a non-root user, "basic" mode requires xrpi to have CAP_NET_BIND_SERVICE capability if any of its server ports on the Linux stack are below 1024. See TCP Ports for more information and workarounds.

To run "normal mode" as a non-root user, the "xrpi" executable needs CAP_NET_RAW capability. See Capabilities for more information.

See also

IP-STACKS -- IP Stacks in XRPi.
TCP Ports -- TCP Server Ports.
IPROUTE.SYS -- IP Routing Tables.
CAPS -- Capability Flags.
XROUTER.CFG(8) -- Main Configuration File.