DHCP fails with two LinkSys BEFSR41s 2

[McGuireV10]

I have DSL connected to a "master" BEFSR41. WAN is DHCP, LAN is 192.168.1.1, mask 255.255.255.0, DHCP server starting at 192.168.1.100, no advanced options configured. LinkSys properly receives DHCP settings from DSL.

A single PC is connected to the master. It correctly receives DHCP assignments and can connect to the Internet normally.

A "slave" BEFSR41 is connected to the master using a cable from one of the master's regular LAN ports to the slave's Uplink port. The slave has WAN set to DHCP (I assume it doesn't matter since the WAN port is unconnected), and the LAN is IP 192.168.1.2, mask 255.255.255.0, DHCP disabled, working-mode set to router, no other advanced options configured.

Two PC's are connected to the slave (not using the shared uplink port) and neither of them can receive DHCP from the master router. Thus, they have no internet connectivity except when I hardcode their IP autoconfig. Currently I'm using a machine with hardcoded autoconfig settings of IP 192.168.1.201, mask 255.255.255.0, gateway 192.168.1.1 (the master IP), and hand-copied DNS IPs. I can ping everything, and I can connect out with these settings, but DHCP fails.

A LinkSys tech support guy told me to set the slave's IP to 192.168.0.1, but without changing masks that just makes the slave LinkSys unreachable. (I assume he meant the LAN IP since the WAN port is unused on the slave.) For now I've ignored his advice and gone back to my earlier settings, as I outlined at the start of this message.

I suspect it's a subnet masking thing, but I'm not sure what exactly I need to do to make everything work right.

What am I missing?

 

[TheOldMan346]

McGuireV10,

Just a stab in the dark here without doing any research. I'd bet the slave router (you're bypassing the router function and just using the switch portion) is blocking it. DHCP is done by way of UDP broadcasts. I'd bet the switch is suppressing the broadcasts resulting in no DHCP. Connectivity is fine since you can do everything when using static IP.

If I get a chance, I'll research further.

Hope that helps. What goes around - comes around.
The Old Man

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[cdogg]

OldMan,
You are definitely full of good ideas, as I've noticed from your other posts. Take a star for your effort!

I still have much to learn about multiple router configurations...


~cdogg

"The secret to creativity is knowing how to hide your sources."
- A. Einstein

 

[TheOldMan346]

cdogg,

Me and Al have our sources. What goes around - comes around.
The Old Man

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[McGuireV10]

OldMan,

By the way, it's probably obvious that I'd like the PCs on each switch to be visible to each other for file sharing and such.

There aren't any settings enabled to block UDP that I can find.

What makes you conclude this setup is not using the router functionality? Would I have to somehow establish each switch as a separate subnet? Not that I'm really sure how to do that, or how to make them visible to each other. I was under the impression that using the Uplink port would automatically involve routing.

Thanks, V10

 

[ceh4702]

According the instructions Linksys says to only run DHCP on one device.

DHCP Is on the Lan side not on the WAN side.

If you want 2 routers, on the setup, I suggest you make the WAN connected router a gateway router and make the other one a normal router. If you connect the switches on the routers with the uplink port you are defeating the purpose of the router. I dont think it is wise to connect 2 routers via their switches. That leaves 2 exit ports open. It also means both switches can run DHCP for each other. You might try changing the addresses of the DHCP so each router is using a different network mask for DHCP that way each router gives out a different set of DHCP ADDRESSES. DHCP can be turned off on one router.

I think your idea on how to connect the routers is fundamentally flawed. I think the best way to do it is to make one router operate a sub-net from the other router by connected the wan port to the other router. You might take a look at the different Network configuration diagrams from the where does it fit in the network to figure this out.

One big porblem is this might not work with Net BIEU because it was not designed for more than one network segment.

What is your purpose in connecting these 2 devices in this way?

Would have been easier to just get a router with more ports on the switch side. The Linksys BEFSR81 has 8 ports and has more added protocols like SNMP and winsock 2.0. If you do not like my post feel free to point out your opinion or my errors.

 

[ceh4702]

If you run 2 DHCP Servers they will give out duplicate IP addresses and both NIC cards will quit working. If you do not like my post feel free to point out your opinion or my errors.

 

[McGuireV10]

The DSL/WAN switch is in gateway mode and is the DHCP server.

The "internal" switch is in router mode and has DHCP disabled.

 

[McGuireV10]

Had more time to read the reply this morning.

The main reason for having two of them is physical separation. The connection between the two involves about 100' of cable. All the ports in the world on a single device wouldn't help there.

I'm just trying to achieve a single simple network where all PC's have the same address range so they can do file sharing over TCP/IP and can all hit the DSL. They can do this NOW if I hard-code the IPs (as I've done on an XP machine's autoconfig settings), it's DHCP that isn't working.

I don't know how NetBEUI got into the discussion. I'm not using it, and since my machines are Win2K Pro or XP Pro, I have no need for it. In fact, it's not even available under XP.

As I noted last night, I do have only *one* LinkSys configured to act as a DHCP server. The other has DHCP disabled. This is the behavior I want -- and that's what isn't working. DHCP isn't getting "through" the second router to the PC's behind it.

I'm not sure what you mean when you say "using the uplink port defeats the purpose of the router." The LinkSys support guy specifically said to connect one of the LAN ports on the master to the uplink port on the slave. Should I connect uplink to uplink, or what?

 

[ceh4702]

If you werent going to use the router for a router, may as well replace it with a switch which is basically what you did by connecting them in that fashion. To do this you might need a DNS server connected to the first router to route between the segments(hubs). Make sure when you assign DHCP on the first router may not be able to see the other computers.

I would acess the router you are using as a gateway and go to the DHCP screen and see if the table can fill up with all the addresses of the devices connected to the second router's switch. When you use DHCP, the router uses a defaust address. I wonder if both routers still use that default address and if it causes conflicts. If you do not like my post feel free to point out your opinion or my errors.

 

[McGuireV10]

I'm ok with just using a switch, I don't think I have any good reason to use routing in terms of features like routing tables, do I? Or am I missing something? (Which wouldn't be surprising...)

What mystifies me is that EVERYTHING else works fine when IP's are hard-coded. DNS lookups, HTTP, FTP, and so on. It's only DHCP that fails, and only on the PC's behind the slave LinkSys.

So it's clearly DHCP that isn't making it "through" that switch.

 

[TheOldMan346]

V10,

Try going into the router's Advanced configuration > Filters page. Enable Multicast Pass Through. I was under the impression that this option referred to the routing functions but, as a general rule, routers do not pass UDP broadcasts anyway. This option may affect the switching functions. It's worth a shot.

Hope that helps. What goes around - comes around.
The Old Man

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[McGuireV10]

Old Man,

Thanks for the suggestion, but multicast pass-through is enabled by default, and I didn't change the setting.

--j.

 

[bobocop]

try to connect the other router to regular port of the first router to the uplink port of the second router, using straight through cable.

 

[mailuser]

Hi Old Man. I have a question for you. I am connecting a Linksys phoneline router (HPRO200) and a Linksys wireless router (BEFW11S4) together. The wireless router has an Uplink port, and the phoneline router does not. Linksys is trying to tell me to go from the cable modem TO the phoneline router, then a normal cable from the phoneline router's LAN jack INTO the wireless router's uplink jack. This sounds backwards to me - wouldn't you go FROM the uplink jack to the other router, rather than from somewhere TO the uplink jack? The word "uplink" to me sounds like it is for output, plus I note that on the wireless router the uplink port is linked with a line drawn to LAN port #4, so I don't see how it could be for input? any suggestions? thanks!

 

[smah]

'Uplink' ports just 'cross over' certain pairs of the individual wires. This port can be both transmit and recieve. You could accomplish the same result, by using a 'cross over' cable connected to a regular port. In your case, port 4 and the uplink port are the same path - just the wires are connected differently. If you use one (uplink) the other (port 4) can't be used because it is actually the same port. That's why the line is connecting those two jacks. The linksys tech is correct - with a straight (normal) cable.

 

[robert187]

could someone please help me? i cant change anything in 192.168.1.1, it has the login set as disable. so now i cant change any settings. i cant even set the damn thing to default. could someone please help me.

 

[cdogg]

There should be a reset button on the front of the router (which depends on the make/model) that you can hit with the tip of a pen or pencil. This will reset the router to its defaults, including the logon.


~cdogg

"The secret to creativity is knowing how to hide your sources."
- A. Einstein

 

[smah]

see thread916-476513

 

[McGuireV10]

On this router, the reset button works two ways. Push it briefly, and it's like a power-off reset -- a soft reset. Push it in and hold it for a long time (I forget how long, 45 seconds or something like that) and it's a hard reset to factory defaults. If I recall correctly, the default password will then be "admin".