• OpenWrtNVRAM

The nvram utility is unavailable in OpenWrt builds based on the 2.6 kernel (at least with the BCM947xx/953xx target), as discussed in these forum threads:

• http://forum.openwrt.org/viewtopic.php?pid=76160

• http://forum.openwrt.org/viewtopic.php?id=6605

If only read access is required, the nvram partition can be read directly, e.g.:

root@harriet:~# cat /dev/mtd4 | grep boot
boot_wait=on
NeedReboot=0

1. IP Interface Settings

In order to configure the IP interfaces on the system, a number of settings are grouped into "bundles" sharing the same prefix. The default bundles are called "lan", "wan" and "wifi", but those names have no special significance other than the fact that the startup script looks for bundles with these names. They might as well have been called "rod", "jane" and "freddy". In fact, let's demonstrate that:

freddy_ifname=vlan2
freddy_proto=static
freddy_ipaddr=192.168.100.100
freddy_netmask=255.255.255.0
freddy_gateway=192.168.100.1

In order to trigger the configuration of this interface, you'd type ifup freddy. This would configure the kernel IP interface vlan2 with the given IP address and netmask, and also insert a defaultroute to 192.168.100.1 via this interface.

(Note: if you are perverse enough actually to want to call your IP interfaces "rod", "jane" and "freddy", you will have to modify /etc/init.d/S40network to call ifup appropriately. This is a useful thing to do if you want to configure extra IP interfaces on your system. You might want to separate off one of your ethernet ports and call it "dmz", for example)

So, let's be sensible and stick to the default "wan", "lan" and "wifi". The WRT54G requires LAN and WAN settings at least to boot properly. Since the "lan" bundle normally consists of the LAN ports bridged together with the wifi interface on the same subnet, most people should leave the wifi_* variables UNSET.

For each bundle you may set the following variables (ie lan_ifname, wan_ifname, wifi_ifname)

Don't set *_gateway more than once, or use *_proto=dhcp on more than one interface, or you'll find yourself with multiple default routes inserted which is probably not what you want.

After changing any of these settings, type ifup foo (where foo is one of lan, wan, wifi etc as appropriate)

2. Bridging

You can create a layer 2 (ethernet) bridge between two or more interfaces by setting foo_ifname=br0 and foo_ifnames="iface1 iface2 iface3...". Typically you will see something similar to this in your default settings:

lan_ifname=br0
lan_ifnames="vlan0 eth1"
lan_ipaddr=192.168.1.1
lan_netmask=255.255.255.0
lan_proto=static
lan_stp=1

In this case, the IP address is assigned to the bridge device (br0), and the bridge device connects interfaces vlan0 and eth1, corresponding to LAN ports 1-4 and the wireless interface respectively.

Note: the network interface names corresponding to physical ports on the Wrt vary from one brand and model of router to another. Your particular device may use different settings to those shown above.

3. VLAN Settings

Because of the way the interfaces are done in hardware (one interface, multiple ports), there are required vlan settings for the device. If these aren't set to the proper values, then the interfaces will not be assigned correctly. Note that if you're using admcfg or similar, this may not apply to you. (I'm not sure).

Be sure the NVRAM has settings for the following, and the recommended defaults:

In other words, an interface called "vlan0" is linked to ports 1-4 of the internal switch (typically labelled "LAN 1-4" on the box, although you may find that they are in reverse order),and an interface called "vlan1" is linked to port 0 of the internal switch (typically labelled "WAN" on the box). Port 5 of the internal switch carries all VLANs tagged (that's what the asterisk is for) to the real interface et(h)0.

PHYSICALLY:
                   tagged     +-------------------+
            eth0 ============ | 5      SWITCH     |
                              | 4   3   2   1   0 |
                              +-------------------+
                                |   |   |   |   |
                                ...LAN 1-4...  WAN

LOGICALLY:
            vlan0 ------------- LAN 1-4
            vlan1 ------------- WAN

If the NVRAM is set with those values, then the recommended values for wan_ifnames and lan_ifnames will be correct. Note that by changing the ports around, you are able to change which port is the WAN port and so on, but that isn't a very good idea in general.

Now let's say you want to syphon off the port labelled "LAN 1" as a DMZ port on a separate subnet. On an Asus router this is actually switch port 4. So you'd reconfigure as:

Once you've done this, you can configure interface vlan2 with its own IP address on its own subnet, and Wrt will route between them.

dmz_ifname=vlan2
dmz_ipaddr=192.168.2.1
dmz_netmask=255.255.255.0
dmz_proto=static

Type ifup dmz to perform the configuration, and modify /etc/init.d/S40network so that this is done when your box is next rebooted too. See DemilitarizedZoneHowto for more details.

Another possibility is that if you don't need a separate WAN port, you could get rid of vlan1 and configure vlan0 so that all 5 ports are on the LAN subnet. Going to the other extreme, you could configure five separate vlans and have a five-port ethernet router.

4. Wireless Configuration

Although the wifi_* variables can be used to configure the IP network settings of the wireless interface, the default setting is to include the wireless interface in lan_ifnames and leave the wifi_* variables unset. If you remove the wireless interface from the lan bridge (which you MUST do to use ad-hoc mode) configure the wifi_* variables according to the general settings above.

There are separate variables called wl0_* which configure the characteristics of the physical wireless interface - which are applicable whether or not the wifi interface is bridged or a separate IP network.

Note: There are wl_* and wl0_* variables; the wl_* variables are obsoleted and were replaced by wl0_*.

For WPA: (See OpenWrtDocs/Configuration on how to enable WPA on current snapshots)

For WEP:

For WDS:

NOTE: if you want to use a wrt54gs as a WDS client with wl0_wds set, the wl0_gmode setting must not be in afterburner (6) mode (apparently no linksys speedboost is available for WDS clients). Also, wl0_mode should be set to ap.

Misc:

In summary, you could find the wifi interface known by three different identifiers: as wl0_* for the physical interface settings, as wifi_* for its IP settings if it's on a separate subnet, and as eth1 or eth2 to the kernel, depending on your hardware. Confused?

5. Static Routes

Static routes are a bit uglier to maintain, but they are still maintainable. Until RC5 there is only one NVRAM setting for them: static_route. This contains all the static routes to be added upon boot-up. From RC6 there can be <ifname>_static_route NVRAM variables for each interface, e.g. lan_static_route.

The syntax of the static_route NVRAM variable is as follows:

  static_route=ip:netmask:gatewayip:metric:interface # until RC5
  interface_static_route=ip:netmask:gatewayip:metric # from RC6

So, for example, to set a static route to 10.1.2.0/255.255.255.0 via vlan1, use:

nvram set static_route=10.1.2.0:255.255.255.0:0.0.0.0:1:vlan1 # until RC5
nvram set lan_static_route=10.1.2.0:255.255.255.0:0.0.0.0:1 # from RC6

This will make 10.1.2.0 directly connected. To route via a router, use:

nvram set static_route=10.1.2.0:255.255.255.0:192.168.1.1:1:vlan1 # until RC5
nvram set lan_static_route=10.1.2.0:255.255.255.0:192.168.1.1:1 # from RC6

This will use vlan1 to send packets to 10.1.2.0 via router 192.168.1.1

As of the most recent CVS build, all values must be present. The networking script doesn't detect missing values, and will thererfore not create the route if the syntax is incorrect (things missing, etc.).

To add multiple routes, seperate each route formatted as above with a space. To avoid the shell truncating after the first space, you need to quote:

nvram set static_route="10.1.2.0:255.255.255.0:192.168.1.1:1:vlan1 10.1.3.0:255.255.255.0:192.168.1.1:1:vlan1" # until RC5
nvram set lan_static_route="10.1.2.0:255.255.255.0:192.168.1.1:1 10.1.3.0:255.255.255.0:192.168.1.1:1" # from RC6

To see if the new settings are working, try

  # ifup lan

If you need to debug this,

  # DEBUG=echo ifup lan

This will list all the commands to be run. You can then copy and paste the "route" command from the output, and run it by hand to see what's wrong.

6. misc

DHCP Settings:

Unsetting these values will not stop the dhcp server from running; it will use default values of dhcp_start=100 and dhcp_num=150. To turn off the dhcp server, use chmod -x /etc/init.d/S50dnsmasq [jffs2 systems] or rm /etc/init.d/S50dnsmasq [squashfs systems]

NOTE: In the unlikely event you're using a lan_netmask other than 255.255.255.0, be aware that dhcp_start is an offset into your network segment, as described by int2ip(ip2int(lan_ipaddr)&ip2int(lan_netmask)). Furthermore, the startup script S50dnsmasq does not allow for the possibility that you might want to run DHCP servers on multiple interfaces, or that you might want to run it on a different interface than lan_*

Hostname:

7. NVRAM committing

When you set/get nvram settings, you are get/setting them in RAM. "nvram commit" writes them persistenly to the flash. But you don't have to commit in order to test, in fact it's safer not to because the flash memory has a limited write cycle life. (Don't be scared though, it's something like 1000-10.000 times; still better to only save it when really needed! NB In Faq it is however stated that this figure, according to manufacturers, can be in the range of 100,000 - 1,000,000) You can save your settings to RAM, check them out by ifdown/ifup'ing all your interfaces, and then "nvram commit" them if they are to your liking. If not, you can reboot and you're back to the last working configuration you had.

You can find out the type of flash chip you have with:

root@OpenWrt:~# nvram get flash_type
Samsung K8D3216UBC 2Mx16 BotB

Here is a table of known flash chips and their endurance according to the manufacturers datasheet:

8. Applying changes to wireless settings

To apply the changes made to the nvram settings that start with wl0_ (e.g. to the wl0_maclist entry) run the wifi command (or wl if you have not installed the wificonf package) to reconfigure the Broadcom wl.o module in the kernel.