should request to 192.168.x.x get out of my router to the WAN?

If I type in my browser and the LAN has no such host, should the router forward this request out to the WAN?

My home network:

DSL--> dlink router --> zyxel wireless router

I thought that a non routeable address like 192.168.x.x is supposed to stay in the LAN and *never* gets out of the router. But one router I bought (ZyXel P334W) is forwarding such address out to the WAN and is causing a problem because the "WAN" is actually my primarly wired ethernet network with a dlink router at, and the "LAN" is the zyxel wireless router which also sits at When I plug in the WAN port, the wireless router stop responding. I have to change the wireless router's default address from to Now, all my wireless laptops can access (reach the login page of) both the zyxel wireless router at and the dlink wired router at

Is this normal?

I was expecting the laptops can access the wireless router but not the wired router.

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That depends not on whether there is such a host, but what the local network is, and how the router is configured. But, is an RFC1918[1] PRIVATE network, so that makes the answer `no'.

Meaning that you have a misconfigured network. You now get to come up with a network plan and configure both devices properly. Whether you set up multiple IP networks and routing or you make one of the devices act like a ``bridge'' between the two networks is up to you[4].

I suggest you familiarize yourself with IP networking, so you might want to read something about it, like [2], and further something that explains NAT[3]. Oh, and what an ethernet bridge is and what it does, too.

[1] Look it up; that document is widely available. [2] Take note that the network address ``classes'' mentioned are a thing of the past, we've moved on to something called CIDR and prefix notation:
formatting link
Network Address Translation, the technique that allows hosts on your RFC1918-numbered lan to talk to the public internet, proprietarily also known as ``masquerading'' and ``internet connection sharing''. [4] As a rule of thumb, routing is usually preferred. As an excercise, try to think of reasons why you would or would not want to bridge.
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comp.protocols.tcp-ip added, where this should really go. (It is an IP question, not an ethernet question.)

192.168.x.x should not route on the public Internet, but, personally, I would expect a small home router to route it. I would be disappointed if it didn't.

Consider the case of double NAT, which sounds like what you have.

If a host on the wireless net, which should be a different (sub)net from the wired net, wants to address a host on the wired net it would need a 192.168.x.y address.

Note that x and/or y must be different on the two nets.

Your ISP router should block it pretty early, or at least before it gets outside the ISPs network.

-- glen

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glen herrmannsfeldt

Correct, since the router has no way of knowing whether the WAN interface is connected to the "public Internet" or some other network that also uses private IPs.

So anything that isn't in the subnet assigned to the LAN will be forwarded to the WAN.

Reply to
Barry Margolin

Thank you all for correcting my misconception.

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Barry Margolin wrote: (snip)

It might be that some router manufacturers get it wrong, though, but double NAT should be legal. My home wireless net runs double NAT through the wired net, both on net 10 subnets.

It does seem that many home routers will only allow subnets down to /24. That is, no more than 254 hosts. I suppose that is a reasonable limit for a home network.

-- glen

Reply to
glen herrmannsfeldt

glen herrmannsfeldt wrote: [snip]

Until your fridge needs an IP, your TV, Audio/Video receivers, blu-ray players..... and the Rowenta iron! ;)

It's a matter of time before everyone will have to buy an 6509 switch! :)

Reply to
Hansang Bae

Hansang Bae wrote: (snip, I wrote)

Or subnets?

I am still waiting for the toaster oven with IP. (I have seen them with RS232 for biology lab use.)

For security reasons it is best to have separate subnets for wired and wireless nets. That gives two subnets already for a house.

-- glen

Reply to
glen herrmannsfeldt

I cannot assert that the toasters were directly connected to IP, my dimm memory doesn't work well that far back, but in the early days of Interop, one of the "staples" of the show flow were SNMP toasters.

rick jones

Reply to
Rick Jones

That's correct. John Romkey (author of SLIP, among other things) did an SNMP-managed toaster (1950's retro style) with an embedded microprocessor and TCP/IP protocol stack. It used a 10BASE2 coaxial cable Ethernet connection to the network. I believe it was demo'ed at the 1988 or 1989 InterOp show.

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