Is it possible to daisychain routers?

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I have a cable modem and a SMC router serving 2 PCs. Now I got another SMC router. Although I had no need for another port, I wanted to experiment. If I connect the 2nd router to one of the ports on the first router using WAN port, I should be able to use all the ports on the 2nd router. After all, I reasoned, it shouldn’t matter from the 2nd router’s point of view whether its WAN connection is to the cable modem or a port of the other router. Well, this didn’t work. I want to know why. To give you an interesting note, I tried the same setup at a different location, except that the 2nd router was Apple’s Airport. This worked easily. Back to the first setup, I tried all sorts of possibilities without any success. Now, is it possible? If so, how? If not, why?
Thank you in advance.

Shlomo

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I have only experience with Linksys, but I would think that if the router doesn’t have a port designated for “uplink” alternative to a hub or additional router, you’d be out of luck. I think it has to do with the wiring – straight through or crossover. What does SMC say about UPLINKING in their documentation or web site?

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Just a thought, as I haven’t done this myself (yet)….

Make sure you’ve disabled the DHCP Service on the second router. Also, ensure the External IP Address (WAN) on the second router is within the same range you’re using on the Internal LAN settings of the first router (on my Linksys, it’s the 192.168.x.x range).

I’d also like you to make sure, you’re using a standard CAT5(e) cable, and NOT a crossover cable. Going from a LAN port on the first router, to the WAN (or UPLINK) port on the second is “a normal connection”.

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Big Al and cbaldrey,

Thank you for your replies.

I called SMC and their tech support simply said they would not support such a configuration without giving me any explanation. The manual for SMC Barricade says nothing about “uplink”. I am aware that what I am trying to do is not a common configuration, but I also know, from my experience with SMC regarding Macintosh compatibility, that they may not know their own product that well.

In any case, if you are still interested (I hope you are), here are some more specifics:

Let’s call the first router (that is connected to the cable modem) Router A and the 2nd Router B.
1. Both routers are SMCs, but one is wireless and the other one not. For this experiment I am not using wireless connection.
2. All the cables I used are Cat5 straight, not crossover.
3. Router A and Router B both have IP Address, 192.168.2.1. Since they both use NAT, this should not matter: each one gets its WAN address automatically from its parent link and assigns IPs to its children with DHCP. But to avoid any confusion, I assigned different IPs. So, it looks like
Router A: WAN IP 24.123.4.5 (from cable company)
LAN IP 192.168.2.1 (default)
DHCP enabled and range is 192.168.2.10 – 20
Router B: WAN IP 192.168.2.11 (assigned by Router A)
LAN IP 192.168.2.2
DHCP enabled and range is 192.168.30-40
4. Let’s say Computer A is connected to Router A and Computer B to Router B. From Computer A I could ping to 24.123.4.5, but from Computer B I could not ping to 192.168.2.1. Why?
5. The reason why I am interested in this configuration is that I need a relay to give internet connection to every room in my apartment. I would like to get another wireless router to use as a relay, but if the above scenario doesn’t work, I cannot use a router as a relay.

I suspect #4 is a telling sign of the problem. Somehow, the connection from a LAN port of Router A is in nature different from the connection from the modem. I would be very much interested in your thoughts. Thank you.

S.

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I’m gonna bail out on you at this point, since I know zero about SMC routers. I would expect the product to have a specific port designate for uplink to another router or hub, as does the Linksys. I do use the uplink on my system from the router to a hub downstairs. I’ll obviously take your word for it that you’ve done it on a MAC system, but I can’t believe that SMC would brush you off that way. Hang in there to see if another Lounger with specific experience on the SMC will jump in.

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Specifically, which SMC router(s) do you have? This would help us in trouble shooting this for you.

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cbaldrey,

SMC Barricade 7004AWBR (wireless) and SMC Barricade 7004ABR. I updated the firmware on both routers to 1.41.004.

Thank you.

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I’m sorry.. I think I was slightly mistaken about the WAN / UPLINK ports. I took a look on my Linksys router, and I have both of these ports.

Reading the literature on the SMC Website, I see that the WAN port is for your direct internet connection.

If I remember correctly, I can not use the number 1 port on my router, when I’m using the UPLINK port. Going with this thinking, if you put a crossover cable between your routers, from one LAN port to another, I THINK you’ll be good to go.

Anyone else have an idea about this?

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The reason you were having problems, is that a router is not just a plain switch or hub. A hub or switch is used to connect computers together on a subnet. A subnet is a LAN. If you look at your TCP/IP settings, you’ll see a Subnet Mask. That ‘mask’, along with your IP Address determines all of the possible IP Addresses on your local subnet. (ie, an IP address of 192.168.0.2 with a subnet of 255.255.255.0 means that the IP Addresses on your subnet are any IP Address with the first three quads of 192.168.0. If your subnet was 255.255.254.0 then your subnet is any IP Address with the first three quads of 192.168.0 and 192.168.1. The Subnet Mask is a binary check. Whatever bits are on for the subnet mask, have to be ‘matched’ on another IP address, to include it in the subnet. (thus 255 means all bits must match, 0 means all bits can be different….254 (last bit is off, so the last bit can be different), etc.).

You can daisy chain switches and hubs together, so that you can increase the size of your subnet. However, to have one subnet talk to another, you need a router. A router is designed to link subnets together. Why? Because when you are using switches and hubs, your computer knows what is on it’s subnet. (Computer Browser). It has no need of a router, to communicate with anything on it’s subnet, because it knows the way already. (The Gateway setting on your TCP/IP settings is the ‘address’ of your subnet’s router). When you request a resource that is NOT on your subnet, THEN you need a router (and a gateway setting pointing to that router). You are then sending your ‘request’ to the router, which determines if what you are looking for is directly on the other side (in the subnet it is linking your subnet with), or if it needs to pass it on to the routers it can ‘see’.

Thus, in what you described, you were putting a router into a router. That means that you now have 2 ‘subnets’, which are not necessarily going to see each other. Also, you can’t have 2 subnets with the same IP range directly talking to each other. (wouldn’t you be confused to try to find 192.168.0.2 if both sides had that IP address?) You may be able to link the LAN ports together, leaving the second WAN port unused.

I hope this wasn’t too confusing.

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Drew,

Thank you for your reply. But I am not sure how your explanation about subnets has to do with my problem. Let’s look at the situation from the 2nd router’s point of view. It has NAT and DHCP is enabled. Its LAN IP address is 192.168.2.2 and its subnet mask is 255.255.255.0. Every PC that is connected to this router gets an IP automatically and it doesn’t have to know what the router’s WAN IP address is or what the 1st router is doing (or even the existence of the 1st router). This router’s WAN connection comes from one of the ports of the 1st router. So, it seems to me that as long as this port gives a good connection to the WAN of the 2nd router, all the PCs under the 2nd router should be connected too. Obviously, something is wrong here, because it is not working. When I connect the 2nd router to one of the ports of the 1st router, I am assuming that I am doing the same thing as when I connect the 1st router to the modem. What is wrong with this assumption? Thank you.

Shlomo

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Okay, let’s say your first router is 192.168.0.1, with a subnet of 255.255.255.0. And then let’s say you have two pc’s on there, 192.168.0.2 and .3. Both of those IP Addresses have a gateway of 192.168.0.1. If you remove the gateway setting, both PC’s on that subnet will still be able to see each other. Why? Because the gateway is only used when an IP Address can’t be found on their subnet. Thus removing the gateway will prevent them from seeing the internet, since they don’t know where to go, to find IP Addresses off of their subnet.

Now, let’s take the second router, you said it’s 192.168.2.2 with a subnet of 255.255.255.0. Let’s put two PC’s on it’s LAN ports, with 192.168.2.3 and .4. Everything above applies, except their gateway is 192.168.2.2. Now plug the second router’s WAN into the first router’s LAN. Nothing will see each other, right? Well, sort of. When 192.168.2.3 is asked to find 192.168.0.2, it goes to it’s gateway (the second router) at 192.168.2.2 and the router takes a look at what is on the other end. IT SEES 192.168.0.2, so it should send the packets to that machine. However, that machine is getting packets with a return address of 192.168.2.3, which it doesn’t see on it’s subnet. So when it goes to return the packets, it is going to send them to 192.168.0.1, which is IT’S Gateway (router). 192.168.0.1 is not going to see 192.168.2.3 on it’s WAN, because it’s WAN is connected to the internet, not the other side of the 192.168.2.2 router.

That means you may be getting communication one way, but not the other. If you have a sniffer, or are running Windows 2000 or XP, you should be able to tell if packets are at least coming from router number 2’s subnet into the first routers subnet.

Now, in theory, all of your computers should be able to see the internet, however, the computers behind the second router may have the same return route issue, that 192.168.0.1 doesn’t know that 192.168.2.2 is a router.

Now, if you don’t use the router as a router, and instead connect one of it’s Lan ports to the first router’s LAN ports, you should be able to get everything to communicate. However, you may have to use a crossover cable to get this to work.

I don’t know your routers personally, but you may be able to tell the first router that it has a router on it’s LAN side. That would get everything working too, but to be honest, I don’t know how to do that on any router at the moment.

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Drew,

Thank you for your patient explanation. It helped me understand the problem better. I suppose what I am trying to do is not really a good idea, but this was a good exercise for me. The whole issue started when I wanted to relay the connectivity of a wireless router to another wireless router in order to cover a wider area. This issue is still unresolved, but I think I should start a separate thread for that. Thanks again.

Shlomo

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Hey no problem. It’s a danger with technology lately. They start making all of these ‘smart’ components, so it seems to be as simple as plugging in your mouse, but their documentation usually gets into the technical stuff at a high ‘techie’ level, so if you need to customize anything, if you don’t have a PhD in networking, you’re up a creek!

Did you try pluggin in Lan to Lan?

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