Various Wireless modes available in Tomato

Discussion in 'Tomato Firmware' started by crawdaddy, Sep 28, 2006.

  1. crawdaddy

    crawdaddy Network Guru Member

    Last night I decided to load a router up with tomato. It looked quite nice, but what confused me was the various wireless modes available in tomato that aren't usually available in other flavors. The standards like AP and Client, Client bridge I understand, but AP and WDS and WDS are the ones I really don't understand. I have had some experience with WDS in DD-WRT, not a lot, but enough to get a short-term link working. So, what is meant by the diffrent WDS modes available in tomato. Thanks
  2. dvaskelis

    dvaskelis Network Guru Member

    Wireless Modes in Tomato

    Access Point (AP) = allow wireless clients (STA) and bridges (WET) to connect to the router

    Access Point + WDS (aka "wireless repeater") = allow wireless clients (STA), bridges (WET), and Wireless Distribution System (WDS) devices to connect to the router

    Wireless Client (STA) = connect router to an Access Point (AP) to receive one IP address only for a hardwired client, no other wireless connections (STA, WET or WDS) are allowed... typically used to give wireless network access to a single hardwired device

    Wireless Ethernet Bridge (WET) = connect router to an Access Point for entire subnet for hardwired clients, no other wireless connections (STA, WET or WDS) are allowed... typically used to give wireless network access to multiple hardwired devices

    WDS (aka "wireless bridge") = only allow Wireless Distribution System (WDS) devices to connect to the router, no other wireless connections (STA, WET or WDS) are allowed... typically used as a wireless bridge between two AP + WDS wireless repeaters
  3. scuba_steve

    scuba_steve LI Guru Member

    Great post. I have been searching for a simple explanation of the modes and this post helped greatly. Unfortunately, it also appears to contradict what I have heard elsewhere on this board about Wireless Ethernet Bridge (WET) mode.

    I read elsewhere that WET mode was good for one hardwired client only (at least reliably), but this post contradicts that position. Could I really use WET mode with multiple hardwired clients? I am shooting for max bandwidth and lowest latency for multiple hardwired clients at the remote router and I do not need to accept wireless clients on the remote router.

    BTW, I apologize if you have already answered similar questions for me on this board...but I am really grasping trying to understand the relative advantages and disadvantages of each mode. :)
  4. danix71

    danix71 LI Guru Member

    Maybe this little dictionary (excellent, BTW) will help you too. :)

    Thanks to Toxic.
  5. scuba_steve

    scuba_steve LI Guru Member

    Thanks danix, but I am still looking for an answer on this one. Believe it or not, I am an EE who writes software for a living. :blush: What I am not, however, is a network engineer. :wink: I get the basic terms...and I know what IPs and MAC addresses are, but subnets etc just bewilder do these modes.

    I am in WET mode now (and things least for one hardwired client on the bridge side), but I have received other advice from smart folks to use WDS, which is more complex to setup...requires specific settings on the AP router...and may not perform as well for multiple wired clients (not sure...just a guess) I was hoping someone who really knows the intended purposes of these nodes can comment.

    I understand that WDS lets you extend the network N number of times...and also has a mode that allows the remote router to also be an AP...but I was wondering if WET mode would be good enough for a Router just intended to be a bridge with multiple hardwired clients...and perhaps perform better (especially with regards to latency). I must say that I do like how easy it was to set WET mode up and that it is easy for me to get to either router's admin screens in a web browser (without having to setup a bunch of port forwarding)....but I want min latency on the far gaming clients on Router 2 don't get slaughtered. :)

    I wish the documentation was much better here...including required subnet, IP ranges, MAC addresses, SSIDs, channels, etc for each mode. I have read GeeTek's test results, but I am still confused as to what the best setup for a bridge client is.

    Anyway, thanks for the link. :thumbup:

  6. GeeTek

    GeeTek Guest

  7. scuba_steve

    scuba_steve LI Guru Member

    Thanks GeeTek. I saw your excellent post where you revealed the results of your testing of each mode...but it seemed to focus on bandwidth, not latency, so I was curious if anyone had any thoughts based on technical knowledge of what each mode needed to do and the overhead required for that routing.

    My real concern, however, is that I have seen some folks say that WET mode doesn't allow multiple hardwired clients on the remote router and other folks (like the second poster here) stating that it is just for that oppose to wireless client mode, which is just for one client. One other person in another recent thread, however, stated that WET mode won't work reliably for multiple clients...and I was wondering if that is the general consensus.

    My empirical results are this - WET mode does seem to support multiple wired clients...and it issues a unique IP to each client from the AP's DHCP server. Gaming performance seems acceptable. Pings don't seem to have suffered by switching from an actual bridge that only supported one device (WET11) to my WRT54GL running Tomato 1.09 in WET mode...with multiple hardwired clients.

    For what it's worth.
  8. GeeTek

    GeeTek Guest

    Optimizing bandwidth will also be optimizing latency. The two are directly related.
  9. Kiwi8

    Kiwi8 LI Guru Member

    Sorry to up this old thread, but I read it through and still can't get the difference between Wireless Ethernet Bridge and Wireless Distribution System. Can any expert explain to me again? :redface:
  10. RonWessels

    RonWessels Network Guru Member

    I realize this quote is old, but I cannot leave it unchallenged. It is demonstrably false. While it is true that bandwidth and latency are often correlated, the two are completely separate concepts.

    For example: let's look at home internet. Say an 8Mbps connection, or 1MBps. The latency is typically down in the 10's to 100's of milliseconds. Let's say less than a second.

    Now consider 10 4GB DVD's put into a car and driven an hour across town. The latency here is an hour, but the bandwidth is 10*4000MB/3600s or 11MBps. This is over 10 times the bandwidth, but also with over 3600 times the latency. Put 20 DVD's in the car and the bandwidth doubles but the latency stays the same.

    To paraphrase a very old signature line back from Usenet days, never underestimate the bandwidth of a car full of DVD's.
  11. dballing

    dballing Addicted to LI Member

    I'm confused a bit about "Wireless Client" mode. It seems like it should be possible to "receive one IP address", assign it to the router, and let the router do DHCP/NAT on the hardwired interfaces (allowing multiple hardwired clients to share the single IP address provided by the upstream AP).

    Now, clearly that may not be how it operates "At the moment", but is there some technical reason this hasn't been implemented? It doesn't *seem*, at face value, to be that different from AP mode. It's basically just changing which interface (WAN vs WiFi) is thought of as the "upstream" port....
  12. GreenThumb

    GreenThumb Addicted to LI Member

    Just to be sure I understand: can the router itself be used as a wireless adapter (for a PC that's hardwired to the router)? I have wondered this for a while.
  13. RonWessels

    RonWessels Network Guru Member

    In Wireless Client (STA) mode, the radio on the router acts just like a wireless adapter. Furthermore, that wireless connection is treated as the "WAN" connection. In other words, wired devices connected to the router will be NAT'ed when their packets are forwarded over the wireless link. Other devices on the wireless network (and whatever it is connected to) cannot talk to wired devices attached to the router without port forwarding having been set up on the router. The router should be configured with DHCP active, since any wired clients should be on a different network address. And since the radio is being used, no wireless clients can connect to the router.

    In Wireless Bridge (WET) mode, again the radio acts like a wireless adapter, and again no other wireless clients can connect to the router. The difference is that wired devices connected to the router are on the same network as the wireless network. That means that DHCP should be turned off on the router, unless you _really_ know what you're doing and are doing something moderately strange.

    The Wireless Distribution System (WDS) is a special protocol that is used to create a point-to-point link between wireless devices. It is very similar to WET mode, except that is is designed for multiple wired clients attached to the router. Strictly speaking WET mode should only support one wired device connected to the router, but almost always multiple devices work. The reason is that an Ethernet packet forwarded in WET mode has the MAC address replaced by the MAC address of the router's radio. That means that multiple devices connected to the router will appear to have the same MAC address to any upstream connection. This works for the most part because the routing of packets coming back has to go through the router anyway, and the router takes care of putting the correct MAC address into the Ethernet packet when it forwards it from its wireless device to its wired device. However, some DHCP controllers will have a problem with this. WDS gets around this by explicitly passing the source MAC address as part of the payload when it forwards the Ethernet packet. The remote WDS connection then forwards that packet with the original MAC address of the source device.

    One other benefit of WDS is that the router's radio is also available to be an access point for wireless clients. This is the WDS+AP mode. But because the radio must first receive the client's packet, then re-transmit that packet to its WDS partner, there is an effective decrease in the overall wireless bandwidth available for wireless clients transmitting packets over the WDS link.
  14. dingmel

    dingmel LI Guru Member

    Sorry for bumping up an old topic, but based on your above explanation, assuming i have a setup as such.

    4 WRT54Gs setup with Tomato, A, B, C and D.
    Router A is hooked up to the Home Network with a few wired devices attached and the DSL Modem as well.

    Router B, C and D are setup at different parts of the home and they're intended to strenghthen the Wifi Signal for internet access (wired and wireless) as well as being able to "talk" to the wired devices attached to Router A ie, printer and Desktops.

    Which option would be ideal for such a setup on Router A and the other Routers? Thanks~!
  15. Kiwi8

    Kiwi8 LI Guru Member

    Either Wireless Ethernet Bridge or Wireless Distribution System will work but I recommend WDS.
  16. RonWessels

    RonWessels Network Guru Member


    Router A would be set up with WAN appropriate for your Internet connection, DHCP enabled, and wireless in mode AP+WDS. The "link to" fields should contain the radio MAC addresses of routers B, C and D.

    Routers B, C, and D are set up with WAN disabled, DCHP disabled, LAN addresses appropriate to the LAN on router A but outside its DHCP allocation range (eg.,, and, default gateway of router A's LAN address (eg. and DNS of router A's LAN address. The wireless mode is also AP+WDS, and the "link to" fields should contain router A's radio MAC address.

    All routers should have the same SSID, be on the same channel, and have the same security settings. Be aware that WPA2 Personal + AES does not work over WDS. I recommend WPA personal + AES.
    scarcasm likes this.
  17. dingmel

    dingmel LI Guru Member

    Thanks Loads Kiwi8 and RonWessels for that brief quick to the point yet through explanation. This forum rocks, period ~

    btw, all the computers would be on the same subnet and should be able to see one another for resource sharing without requiring any port forwarding, yes? in other words, computers connected to either one of the routers would see each other as in one large network?
  18. danix71

    danix71 LI Guru Member

    Yes. Computers and the routers/WDSin the same LAN should see each other (on one computer one can access the main router and the least that's happen' at my home. :)

    Ex: Router with AP+WDS on wireless part-
    NSLU- (wired, conn. to router)
    Computer 1- (wireless, desktop)
    Computer 2- (wireless, mobile)

    Once again: be aware that DHCP is ON only on router NOT on WDS.
  19. Kiwi8

    Kiwi8 LI Guru Member

    Actually all the routers can put in MAC addresses of the other three routers, though they need to all enable Spanning Tree Protocol. This makes it more flexible depending on whether there is a need to do big data transfers without the main router as the bridge root can be easily changed. However, if there is little need for such transfers, then it is fine using Router A as the main router.
  20. Kiwi8

    Kiwi8 LI Guru Member

    Yes, they are all in the same subnet as they are bridged. Of course, the usual port forwarding is still needed for unsolicited WAN-side traffic to access the network. :)
  21. scarcasm

    scarcasm Reformed Router Member

    Thank you for this. Helped me set up my Tomato routers perfectly.

    Sorry for bumping an ancient thread.
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