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Gateway vs. Router mode

Discussion in 'Networking Issues' started by jlindema, Jan 16, 2006.

  1. jlindema

    jlindema Addicted to LI Member

    Hi Everyone-

    Advance apologies if this question has already been answered. Here goes!

    There seems to be a lot of confusion between a "gateway" and a "router".

    A traditional "gateway" can mean a device that (sometimes) is able to route traffic, but
    whose primary goal is to *translate* from one protocol to another. For example- I would
    use a "gateway" if I wanted to send packets from my IPv4 network to/from a IPv6 network,
    or maybe an AppleTalk network to/from a Token Ring network.

    A router knows about all of the networks to which it is connected, perhaps it knows
    about its next-hop (default gateway), etc. -and it makes *decisions* to which interface
    a packet must travel to get that packet on its way to its destination. It may also
    support "gateway" features, but the primary goal of a "router" is to intelligently
    forward traffic from one interface to another... not necessarily to *translate* from one
    protocol to another.

    Now, finally to the gist of my question :D -

    When speaking about a simple in-home, ADSL-modem connected to a Linksys (...Let's say a
    WRT54GS), what does Linksys consider the difference between its "gateway" and "router"
    operating mode?


    In my scenario I have a WRT54GS's WAN port connected to my DSL modem, it's 'default
    gateway' is configured to point to the next-hop (the far side of my ISP's DSL/network),
    the WRT54GS is in GATEWAY mode... and everything on my LAN/Wireless side works
    perfectly. Access to the Internet works... and everything on my LAN and Wireless network
    can 'see' and talk to everything.

    Now- if I switch the WRT54GS to "ROUTER" mode, I no longer can access the Internet ...or
    even ping my default-gateway. For example, let's say my ISP has assigned me
    192.168.254.36 255.255.255.252. My DSL modem has 192.168.254.37, and my WRT54GS's WAN
    port has 192.168.254.38.

    Since my Linksys is not doing any protocol translation (it's all Ethernet!), and I'm
    'statically' configuring my default gateway (192.168.254.37), and local networks... I
    don't need any routing protocol (i.e. RIP on the WRT54GS is disabled).

    It's my understanding that ROUTER mode *should* work.
    Obviously I'm missing something very fundamental- since it doesn't seem to work (can't
    even ping 192.168.254.37) unless I switch the WRT54GS back to GATEWAY mode.

    So - my question:
    What *specifically* does Linksys consider the difference between GATEWAY and ROUTER
    mode?


    I guess I need a lot more detail... not just "If the router is hosting your Internet
    connection, select Gateway mode. If another router exists on your network, select Router
    mode".

    Sorry for the long-winded post and thanks to anyone who can help me understand this
    better! :shock:

    -John
  2. _Jeff_

    _Jeff_ Addicted to LI Member

    Did your ISP provide you with a block of routable IPs?
  3. jlindema

    jlindema Addicted to LI Member

    _Jeff_,

    Yes- my ISP is providing a routable block of addresses. The ones used above were an example only.

    When my WRT64GS is in "gateway" mode, everything works fine (and configured using my ISP's real, routable addresses).

    When configured using those same, real/routable addresses- in router mode, I cannot ping my ISP's default gateway, [therefore...]much less access the Internet.

    Thanks,
    John
  4. itdaddy69

    itdaddy69 Addicted to LI Member

    money

    hey doesnt your isp service routeable block address cost big bucks?
    you must be rich..
    robert;
  5. reopeadres

    reopeadres LI Guru Member

    ok
    you need to set up your routing in your router that is not connected to the internet and tell it to forward the packets on the wan side to the ap on the internet connection:)
  6. scotkb

    scotkb LI Guru Member

    I think that if you connect using a LAN port when you have the WRT in router mode, that it will work. My understanding is that the WAN port is only for gateway mode (unless you have been playing with the VLANs, etc with 3rd party firmware).
  7. jlindema

    jlindema Addicted to LI Member

    Hello everyone-

    itdaddy69, no... I'm far from wealthy. I managed to get in early, and at least for the time being, I'm keeping my routable, static address. Of course it's all up to my ISP :thumb: -about $110/month, shared between a roommate and work.

    scotkb, -very interesting idea. I hadn't considered that configuration since I figured the NATting and firewall capabilities would be bypassed if I connect directly to the LAN ports.
    If that's the case, then I don't want to do it. Maybe for testing, but not for any long-term configuration.

    So I'm guessing the Gateway mode provides the NAT/firewall functions- where Router mode only forwards traffic between wireless/LAN ports (but not WAN)?
    If that's the case, the "operating mode" should be labeled "Gateway" and "10/100 Switch". There's essentially no intelligent choices for the WRT54GS "router" to make unless the WAN port is included. ???

    Thanks for the replys-
    John
  8. Couledouce

    Couledouce LI Guru Member

    I believe in Linksys WRT terms, "gateway" simplely means a gateway to the internet.
  9. YeOldeStonecat

    YeOldeStonecat LI Guru Member

    Not correct. You use the WAN/Internet port if in "router" mode. I've setup some Linkies on our WAN with frac Ts, using router mode.

    To answer your question jlindema, home market broadband routers such as this Linksys....well, the term "router" has come to be a household term these days with the explosion of broadband. It has evolved to mean something a bit different than the term "router" used to mean years ago, when it was only seen as a geeks device in connecting wide area networks in enterprise networks. Home broadband routers have evolved to actually be combination devices of a router, NAT box, and built in 4 or more port switch, and optional access points. Home broadband routers are generally designed to be run in "gateway mode"...which means it's running NAT, and will take a single WAN IP address, and share it to up to 253 computers on the LAN side. It's the networks "gateway to the internet"..gateway is more commonly used to decribe the hop between a LAN and the internet.

    "Router mode" is more for wide area networks and large networks...to tie them all together. That's the main job of a router "to route networks...connect them".

    Also with the Linksys, depending upon how your ISP is setup, you'll probably have to remove the checkbox for "Block WAN request"...as their routers need to stay in touch with the Linky.
  10. jlindema

    jlindema Addicted to LI Member

    Any additional advice?

    Thanks- Couledouce, YeOldeStonecat, and everyone for the replys.

    OK- so I can deal with the terms gateway and router having drifted from their "classic" meaning.

    What I still can't seem to figure out is why I can no longer ping my default gateway (my ISP's side of my /29 routable subnet) when I change the WRT54GS to "router" mode.

    I don't think I need RIP (and doubt it's even being sent to me via my DSL modem or an upstream router)... and all of my routes appear to be in place from the Linksys's main config. page [and after clicking "Show Routing Table"]

    With the WRT54GS in "router" mode, routes in place and accurate for LAN/WLAN, WAN and 0.0.0.0/0.0.0.0 -I can't ping my default gateway.

    Switch back to "gateway" mode, *don't touch anything else*, and viola! I have connectivity.

    That just doesn't make sense!!!??

    Unless- the WRT is doing something with it's MAC address after the "operating mode" change.
    Hmmm... if that's the case, then my DSL modem may need to do a re-ARP -before everything clears up.
    I also need to try YeOldeStonecat's suggestion of un-checking "Block WAN request".

    It's late tonight -I'll do some more testing soon.
    :)
  11. SuperDucIe

    SuperDucIe Guest

    I had the same problem with my wrt54g. But I didn't have this problem until I upgraded my firmware. I could not ping the anything beyond the router from my computer while setup in “router†and everything worked when I switched back to “gatewayâ€. I cannot ping the internet from my computer, but when I used the ping utility on the router to ping the internet and it worked. So the router is simply not routing the packets.

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