Q: Can I have more than one router in a network?
Best Answer: Turn off DHCP on the second router, and do not use the WAN port. Just plug the LAN port into the first router, and the second router will act as a switch only.
Set the second router's address to 192.168.0.2, so you can still get to it to administer it… All PCs will then be in the 192,168.0.x subnet.
If you need more ports, add a cheap switch to either the first or second router.
Re:What is a colo provider?
Co-location.
Your hardware, their building.
Places scale all the way from "some guy with a couple T1's and some shelving" up to that one place that declared itself an independant country out on an oil rig somewhere near england.
They can typically offer services such as a giant UPS backed by generators, multiple internet backbone connections, fire protection, and security.
bart
Re:Again it would be helpful to know why the question is being asked. A lot of times, people ask this sort of question because they happen to have 2 routers and what they really want to know is whether the 2nd one can be used as a switch only. But, as the responses above indicate, some people have needs that are a lot more complicated than that!
Anyway, this is interesting, even if I don't follow all of it. What is a colo provider?
Re:1) You can most certainly have more than one router on any given network, unless it has a 30 bit subnet mask, in which case you will have two routers, with zero nodes, which doesn't make sense unless you're strictly routing between networks (which absolutely does make sense, but not in the case that you'll probably ever see if you're asking the question – or unless you just want to route from one cable segment to a DSL segment etc.. but I can't imagine a practical use for such a crude setup)
Judging from guy's other post's he's probably talking about in a colo environment, no cable or DSL bullcrap here.
2) While it may not be feasible to have two routers, you can easily adapt the nodes on your network for a very basic type of 'failover' if you have more than one connection. Set the default route for your primary circuit with a metric of 1, set the other route to the secondary router with a metric of > 1.
Since most people spend a lot of $$ on colo space, he'll most definitely want to have layer 2(spanning tree on his switches) and layer 3(VRRP or HSRP on his routers) redundancy. He mentioned using openbsd as the firewall, he won't have any redundancy since cisco claims its patent on hsrp extends to vrrp IIRC. FreeBSD has freevrrpd, but it doesn't set the MAC addresses right for the VRID interface so you would have to wait for an arp cache clearing for traffic to start flowing again.
) Let's say that you want to trunk the bandwidth across two connections – you'll most certainly need two routers to do this, but they don't necessarily have to be on the same network. Indeed, they can be on the same LAN internally; however, your external sides will need to be on different networks to be effective.
Traditionally trunks have either been isl or dot1q, some people erroneously refer to 802.3ad link aggregation as trunking, but that just confuses people as they are 2 different things. I'm sure his colo provider could provide redundant physical links to his cabinet for an added cost.
LASTLY, and probably beyond the scope of the original argument, traffic trying to reach back INTO your network will only be able to come in from one path, or the other, unless you have configured BGP4 for them (which I *HIGHLY* doubt you have as just the setup cost alone is more than your best computer – this doesn't include the hardware necessary to do it either (bah, ZEBRA for linux… free.. scrap the hardware costs.. ). Along the lines of this thought, you could also check out www.rainfinity.com, specifically their rainconnect software. At this point, I'm pretty sure that this information has well eclipsed the scope of your project so I'll just shut up now.
I'm sure his colo provider is not some 2bit operation, so everything coming into and inside the datacenter would be redundant as well.
Re:heh, I had a lot of stuff typed out to but then I decided, "simple question, simple answer" and went with my reply
Re:1) You can most certainly have more than one router on any given network, unless it has a 30 bit subnet mask, in which case you will have two routers, with zero nodes, which doesn't make sense unless you're strictly routing between networks (which absolutely does make sense, but not in the case that you'll probably ever see if you're asking the question – or unless you just want to route from one cable segment to a DSL segment etc.. but I can't imagine a practical use for such a crude setup)
2) While it may not be feasible to have two routers, you can easily adapt the nodes on your network for a very basic type of 'failover' if you have more than one connection. Set the default route for your primary circuit with a metric of 1, set the other route to the secondary router with a metric of > 1.
3) Let's say that you want to trunk the bandwidth across two connections – you'll most certainly need two routers to do this, but they don't necessarily have to be on the same network. Indeed, they can be on the same LAN internally; however, your external sides will need to be on different networks to be effective.
LASTLY, and probably beyond the scope of the original argument, traffic trying to reach back INTO your network will only be able to come in from one path, or the other, unless you have configured BGP4 for them (which I *HIGHLY* doubt you have as just the setup cost alone is more than your best computer – this doesn't include the hardware necessary to do it either (bah, ZEBRA for linux… free.. scrap the hardware costs.. 
). Along the lines of this thought, you could also check out www.rainfinity.com, specifically their rainconnect software. At this point, I'm pretty sure that this information has well eclipsed the scope of your project so I'll just shut up now.
Enjoy!
Re:It's gonna depend on what you intend to do with them. I have two (well, three actually): a PIX, a LinkSys '41, and a Cisco 2611. All are manually addressed on the inside, all get DHCP addresses from my provider (AT&T Cable). I use the PIX primarily for VPN access, the LinkSys primarily for inbound SSH, and the 2611 for external access to a practice rack. All computers except the SSH server are using the PIX as a default gateway, the rack is not set up for outbound access. The SSH server is using the LinkSys as a default.
So two firewalls in parallel work fine, but you aren't likey to be able to use the "automatic" features of both concurrently. You'd also need an extra address assignment from your provider. You won't get any extra bandwidth, you probably won't get any extra efficiency. I'm doing it for convienience for a specific feature/protocol so I can add a little extra security on the open port.
Putting two firewalls in series will also probably work, but it's not going to be an automatic configuration. If both firewalls are using the same DHCP address ranges, then the users behind firewall #2 would be on the same address block as the users of firewall #1 – routers won't route to the same address block.
So, you'd have to set up the users of firewall#2 to use a different address block (maybe 192.168.100.X – anything that's not the same as #1's addresses – a different network or subnet number).
Nearly anything can be done, the questions are "Why do you want to do it (what do you expect to gain)?" and "Is it worth the bother?"
For most home users, there isn't much, if anything, to gain and it's usually not worth the bother beyond "IWBC" (It Would Be Cool).
FWIW
Scott
Re:Why would you want or need more than one router on your network?
One router will support many users (I forget how many, 200+?).
Re:I bet with the right subnetting and static routing I could get IP based services flowing just fine. Now for Microsoft File Sharing that I probably could get to work eventually (not that I would want to use it). You could essentially have them work perfectly if all you wanted was web and e-mail. This all bearing on what devices you're using but most of the entry levels are carrying the same features these days.
Re:Originally posted by: guy
Originally posted by: guy
Regular Home Entry Level Routers, and regular Cable or DSL, it probably will not work..Why do you say that?Depending on the setup there can be few reasons.
For one, in order to use two Entry Level Cable/DSL Routers as Routers, the second Router needs to be connected through the WAN port. The NAT (firewall) in the second Router will not let any other computer on the first part of the Network to initiate communication with the part of the Network that is behind the second Router?s firewall (and NO you can not disconnect the firewall on Entry Level Cable/DSL routers).
Re:Originally posted by: guy
Regular Home Entry Level Routers, and regular Cable or DSL, it probably will not work..
Why do you say that?
Re:I think we need a little more information about your setup. I got a 2nd router cheap. Since I didn't need the routing features, I disabled dhcp on it, and just used it as a switch. I couldn't get it to work right until I did that. So, what kind of setup do you have, and why do you want to use 2 routers? I don't think the typical home network needs 2 routers.
Re:Regular Home Entry Level Routers, and regular Cable or DSL, it probably will not work..
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