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Author Topic: Using a router as a switch  (Read 4893 times)

Riley Casey

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Using a router as a switch
« on: November 06, 2014, 05:46:32 pm »

THis is a follow up to an earlier thread about wired routers for use with Shure UHF-R systems.  I found a few older Netgear FVS318 routers on Ebay at a price that made experimentation painless and a size the JUST barely fits into the rack.  Reset the parameters and it all works like a charm with four receivers per rack and easy access to connect a laptop for WWB duties.  Now prior to starting this process I had done some Googling on the topic of disabling DHCP on routers to turn them into switches and I planned to do that on these routers when I needed to connect multiple racks.  Simply connect to router B , turn off DHCP and restart then connect the laptop to router A and connect a port on router A to a port on router now switch B.  Lotsa sites on Google say no problem except it doesn't work.  Both routers work normally but the switch only router is not passing IPs thru to the receivers in its rack.  Any network gurus have an idea as to what might be the issue?

frank kayser

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Re: Using a router as a switch
« Reply #1 on: November 06, 2014, 05:53:31 pm »

THis is a follow up to an earlier thread about wired routers for use with Shure UHF-R systems.  I found a few older Netgear FVS318 routers on Ebay at a price that made experimentation painless and a size the JUST barely fits into the rack.  Reset the parameters and it all works like a charm with four receivers per rack and easy access to connect a laptop for WWB duties.  Now prior to starting this process I had done some Googling on the topic of disabling DHCP on routers to turn them into switches and I planned to do that on these routers when I needed to connect multiple racks.  Simply connect to router B , turn off DHCP and restart then connect the laptop to router A and connect a port on router A to a port on router now switch B.  Lotsa sites on Google say no problem except it doesn't work.  Both routers work normally but the switch only router is not passing IPs thru to the receivers in its rack.  Any network gurus have an idea as to what might be the issue?
Are you using just the LAN ports?  You will want to avoid using the WAN port in any hookup on any router other than the one connected to the cable modem or DSL connection.  I'm assuming you're not using it to connect to the internet, therefore there probably shouldn't be any WAN port connection.
« Last Edit: November 06, 2014, 05:55:59 pm by frank kayser »
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Chris Hindle

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Re: Using a router as a switch
« Reply #2 on: November 06, 2014, 08:17:36 pm »

Make sure each one has a unique IP address??
Switches don't have addresses, but routers do. Maybe that is getting in your way .....
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Tom Bourke

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Re: Using a router as a switch
« Reply #3 on: November 07, 2014, 12:33:41 am »

Are you using just the LAN ports?  You will want to avoid using the WAN port in any hookup on any router other than the one connected to the cable modem or DSL connection.  I'm assuming you're not using it to connect to the internet, therefore there probably shouldn't be any WAN port connection.
You can also set the WAN port to bridged mode.  DDWRT can also use the WAN port as part of the switch.  I am not sure if DDWRT runs on that router or not.
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Rob Spence

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Re: Using a router as a switch
« Reply #4 on: November 07, 2014, 12:36:25 am »

Just turning off DHCP doesn't make a router into a switch.


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Andrew Hollis

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Re: Using a router as a switch
« Reply #5 on: November 07, 2014, 11:27:07 am »

Based on clues in the post, I don't think DDWRT is the road to go down here...

Rob and Chris's comments are sensible.

A router with multiple ports is always a switch, regardless of DHCP status. If you just needed a switch just get a switch. One buys a router so that one may use DHCP, that's the whole point of a router most of the time.

Frankly, DHCP is more useful, I don't know why one would disable it. If you want permanent addressing, use the static DHCP addressing within the router.

The mistake I believe you made is you turned off DHCP but didn't then go to each client and manually assign fixed IP addresses on a common subnet for each--which seems to me more trouble than using DHCP and letting that take care of it automatically.

Also, multiple routers is generally not necessary unless you have a specific need to separate multiple devices from each other, which I doubt you do in this case.

frank kayser

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Re: Using a router as a switch
« Reply #6 on: November 07, 2014, 11:58:46 am »

Based on clues in the post, I don't think DDWRT is the road to go down here...

Rob and Chris's comments are sensible.

A router with multiple ports is always a switch, regardless of DHCP status. If you just needed a switch just get a switch. One buys a router so that one may use DHCP, that's the whole point of a router most of the time.

Frankly, DHCP is more useful, I don't know why one would disable it. If you want permanent addressing, use the static DHCP addressing within the router.

One can only have one DHCP server on the local net.  If he's already has a router, and wants this one to just operate as a switch, and the first router has DHCP enabled, then the second router must have DHCP disabled.
frank
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Brian Jojade

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Re: Using a router as a switch
« Reply #7 on: November 07, 2014, 12:02:41 pm »

Turn off DHCP and don't use the WAN port.  Then the remaining ports on the device will behave as a switch. The router functions will still be there, but since you're not using them, it won't matter.  If you use the WAN port, you are running through the router and different configurations would be needed.
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Brian Jojade

Brian Jojade

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Re: Using a router as a switch
« Reply #8 on: November 07, 2014, 12:03:28 pm »

One can only have one DHCP server on the local net.  If he's already has a router, and wants this one to just operate as a switch, and the first router has DHCP enabled, then the second router must have DHCP disabled.
frank

Sort of.  You could have multiple DHCP servers on the network with different IP ranges being handed out.  Pretty common on larger networks.
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frank kayser

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Re: Using a router as a switch
« Reply #9 on: November 07, 2014, 12:11:41 pm »

Sort of.  You could have multiple DHCP servers on the network with different IP ranges being handed out.  Pretty common on larger networks.
I stand corrected.  Thanks!
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Simon Hutson

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Re: Using a router as a switch
« Reply #10 on: November 07, 2014, 12:59:03 pm »

Make sure each one has a unique IP address??
Switches don't have addresses, but routers do. Maybe that is getting in your way .....

I agree. If you reset both units, they will both default to the static IP address 192.168.0.1 (regardless of the DHCP settings). When you connect unit A to unit B, each unit will detect an IP address conflict and shut down the offending Ethernet port.

Try setting the IP address of unit B to 192.168.0.2, enable DHCP on unit A, Disable DHCP on unit B and make sure your starting DHCP address on unit A begins at 192.168.0.3 so it doesn't conflict with the unit B static address.

Let me know how you get on.

Best regards, Simon
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Scott Holtzman

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Re: Using a router as a switch
« Reply #11 on: November 07, 2014, 01:30:42 pm »

Sort of.  You could have multiple DHCP servers on the network with different IP ranges being handed out.  Pretty common on larger networks.

No, that's not accurate.  Larger networks are broken into smaller networks for a number of reasons.  To me a network is a single collision domain for this discussion.  In these large mult segment configurations the switches will use a trunking protocol to isolate the segments from a layer two perspective.  The protocol is IEEE 802.1q  A single DHCP server can answer requests from multiple networks and the router on each segment (usually one router) uses IETF RFC-3046 DHCP relay to forward the DHCP requests from each LAN segment to the central DHCP server.

DHCP protocol straddles layer 2/3 - The offer/request format uses broadcast Ethernet Frames at Layer 2, it hands out IP addresses which are required for Layer 3 communications.

With regards to the OP and topic.

The switches built into routers are of marginal quality compared to a dedicated switch at all.  Certainly they may not be non-blocking (wire speed available across the entire matrix).

A quality switch is managed and non-blocking, supports port prioritization and other features useful for live audio.

In the worst of situation I have seen consumer level routers that the ports are just a hub.

Switches are cheap.  It's not worth the savings for the possible problems.

If you need wireless go with a switch and an discrete access point.



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Scott AKA "Skyking" Holtzman

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Riley Casey

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Re: Using a router as a switch
« Reply #12 on: November 07, 2014, 01:51:01 pm »

Thanks for all the responses, especially the conflicting ones!  Apparently I should have described this deployment a little better.  I have three racks each loaded with multiple UHF-R receivers. More than half the time these racks will go out stand alone but of course on larger show they may be used in combinations.  The intention with installing the switches was to have a plug and play box that any show tech could connect a laptop to and have Wireless workbench find all available units with no reconfiguration of the hardware or the computers' network configuration.  The multiple racks on a single show scenario was that DHCP could be disabled on one or more racks and the one router still configured for DHCP could pass out IPs as needed with the disabled routers acting as switches.  The physical space available in these existing racks doesn't allow for both a switch and a router.  There is no need for wifi capability nor space for antennas. The speed requirement is low, it's all pretty minimalist intentionally. I have tried bumping the base IP of the routers 30 digits apart in hopes that this would eliminate conflicting addresses but that didn't seem to make a difference to the current problem of no access to units connected to the second router/ switch.

Simon Hutson

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Re: Using a router as a switch
« Reply #13 on: November 07, 2014, 02:07:47 pm »

Thanks for all the responses, especially the conflicting ones!  Apparently I should have described this deployment a little better.  I have three racks each loaded with multiple UHF-R receivers. More than half the time these racks will go out stand alone but of course on larger show they may be used in combinations.  The intention with installing the switches was to have a plug and play box that any show tech could connect a laptop to and have Wireless workbench find all available units with no reconfiguration of the hardware or the computers' network configuration.  The multiple racks on a single show scenario was that DHCP could be disabled on one or more racks and the one router still configured for DHCP could pass out IPs as needed with the disabled routers acting as switches.  The physical space available in these existing racks doesn't allow for both a switch and a router.  There is no need for wifi capability nor space for antennas. The speed requirement is low, it's all pretty minimalist intentionally. I have tried bumping the base IP of the routers 30 digits apart in hopes that this would eliminate conflicting addresses but that didn't seem to make a difference to the current problem of no access to units connected to the second router/ switch.

OK, understood. You could have DHCP enabled on each individual router so long as the base addresses of each router are unique, the DHCP address ranges on each router don't overlap with each other or the base addresses, and all addresses are on the same subnet. That should enable you to run the racks standalone or in combination without any configuration changes (I think).

Best regards, Simon
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frank kayser

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Re: Using a router as a switch
« Reply #14 on: November 07, 2014, 02:11:14 pm »

Thanks for all the responses, especially the conflicting ones!  Apparently I should have described this deployment a little better.  I have three racks each loaded with multiple UHF-R receivers. More than half the time these racks will go out stand alone but of course on larger show they may be used in combinations.  The intention with installing the switches was to have a plug and play box that any show tech could connect a laptop to and have Wireless workbench find all available units with no reconfiguration of the hardware or the computers' network configuration.  The multiple racks on a single show scenario was that DHCP could be disabled on one or more racks and the one router still configured for DHCP could pass out IPs as needed with the disabled routers acting as switches.  The physical space available in these existing racks doesn't allow for both a switch and a router.  There is no need for wifi capability nor space for antennas. The speed requirement is low, it's all pretty minimalist intentionally. I have tried bumping the base IP of the routers 30 digits apart in hopes that this would eliminate conflicting addresses but that didn't seem to make a difference to the current problem of no access to units connected to the second router/ switch.
You really have three separate networks running there. You want to manually combine them at times (by substituting a switch for a router - functionally), and run it as three nets at other times.  Why not combine the tree networks with a bridge - they can still function as the three nets, but can be addressed through the single cable without reconfiguring the routers each time.
frank
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Scott Holtzman

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Re: Using a router as a switch
« Reply #15 on: November 07, 2014, 03:03:06 pm »

Thanks for all the responses, especially the conflicting ones!  Apparently I should have described this deployment a little better.  I have three racks each loaded with multiple UHF-R receivers. More than half the time these racks will go out stand alone but of course on larger show they may be used in combinations.  The intention with installing the switches was to have a plug and play box that any show tech could connect a laptop to and have Wireless workbench find all available units with no reconfiguration of the hardware or the computers' network configuration.  The multiple racks on a single show scenario was that DHCP could be disabled on one or more racks and the one router still configured for DHCP could pass out IPs as needed with the disabled routers acting as switches.  The physical space available in these existing racks doesn't allow for both a switch and a router.  There is no need for wifi capability nor space for antennas. The speed requirement is low, it's all pretty minimalist intentionally. I have tried bumping the base IP of the routers 30 digits apart in hopes that this would eliminate conflicting addresses but that didn't seem to make a difference to the current problem of no access to units connected to the second router/ switch.

Ok got it.

Here is what you want to do.

In the three racks on the inside (LAN or trusted side of the router/switch your network is connected to utilize the following IP networks with DHCP.

Rack 1 - 10.10.1.0/24 - GW 10.10.1.1 Subnet Mask 255.255.255.0 DHCP range 10.10.1.20-99
Rack 2 - 10.10.2.0/24 - GW 10.10.2.1 Subnet Mask 255.255.255.0 DHCP range 10.10.2.20-99
Rack 3-  10.10.3.0/24 - GW 10.10.3.1 Subnet Mask 255.255.255.0 DHCP range 10.10.3.20-99

On the WAN side number as follows -

Rack 1 - Interface IP 10.1.1.1 Subnet Mask 255.255.255.128 GW 10.1.1.126
Rack 2 - Interface IP 10.1.1.2 Subnet Mask 255.255.255.128 GW 10.1.1.126
Rack 3 - Interface IP 10.1.1.3 Subnet Mask 255.255.255.128 GW 10.1.1.126

In the rack most likely to be deployed on mult-rack jobs get a small enterprise router and on one interface put 10.1.1.126 Subnet Mask 255.255.255.128

Now on that router you need 3 routes

ip route 10.10.1.0 255.255.255.0 10.1.1.1
ip route 10.10.2.0 255.255.255.0 10.1.1.2
ip route 10.10.3.0 255 255.255.0 10.1.1.3

That router will now be a traffic cop and direct traffic between the 3 networks and devices can be plugged into the switch in all three cabinets.

I recommend a Cisco 17xx router.  It will survive a nuclear bomb and can be had on the used market for less than $50.00






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Scott AKA "Skyking" Holtzman

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Chris Johnson [UK]

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Re: Using a router as a switch
« Reply #16 on: November 07, 2014, 03:22:28 pm »

I suspect the problem here is that you are involving the WAN port.

Technically speaking, the 'router' you bought is probably actually a 2 port router with a 5 port switch bolted on the side. Meaning that the routing happens between the WAN port, and an internal LAN port, and then the LAN port is connected to a 5-port switch chip that drives the 4 'LAN' ports on the back.

By default, devices on the LAN side of the router won't be able to receive DHCP addresses from a router on the WAN side. But that behaviour may be able to be changed.

The short answer is, though, why not just use a switch?
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Ade Stuart

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Re: Using a router as a switch
« Reply #17 on: November 07, 2014, 04:12:14 pm »

The short answer is, though, why not just use a switch?
+1
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Jeff Hague

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Re: Using a router as a switch
« Reply #18 on: November 07, 2014, 04:39:38 pm »

I suspect the problem here is that you are involving the WAN port.

Technically speaking, the 'router' you bought is probably actually a 2 port router with a 5 port switch bolted on the side. Meaning that the routing happens between the WAN port, and an internal LAN port, and then the LAN port is connected to a 5-port switch chip that drives the 4 'LAN' ports on the back.

By default, devices on the LAN side of the router won't be able to receive DHCP addresses from a router on the WAN side. But that behaviour may be able to be changed.

The short answer is, though, why not just use a switch?


Exactly!

What the OP describes will work provided that he disable DHCP on all but 1 of the routers, set non conflicting static addresses on each router AND connect everything to LAN ports - do not use the WAN ports at all.
If router A is the DHCP server and is connected to router B via a WAN port (WAN port on both routers or WAN on 1 and LAN on the other - doesn't matter), clients on router B will not get addresses from DHCP. DHCP discover packets are broadcasts and routers block broadcasts. The WAN port on these consumer wifi devices IS the router. If the 2 routers are connected via LAN ports only, broadcasts pass and DHCP will work.
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Mitch Miller

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Re: Using a router as a switch
« Reply #19 on: November 07, 2014, 04:55:21 pm »

Short reply is because he has multiple IP networks he's trying to combine at certain times with minim reconfiguration.

Holzman's reply above would be the best zero configuration design, IMO.

If everything was using static IP addresses in a single subnet, and if the switches (yes, the multi-port section of your router is a switch) have crossover jacks (not all do), one should be able to connect each switch to the other and all the devices could talk with each other. And in this configuration, it wouldn't matter if you had DHCP enabled or not since no one would be using it. But, it would require some planning and sticking with the plan to make each network function as well on its own, as well as when combined (mostly so there'd be no IP address clashes).
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Tim Padrick

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Re: Using a router as a switch
« Reply #20 on: November 09, 2014, 05:50:47 pm »

This setup works.  See if this is of any help: http://padrick.net/LiveSound/IPaddys2.jpg
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Scott Holtzman

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Re: Using a router as a switch
« Reply #21 on: November 10, 2014, 12:06:09 am »

Tim, that won't work for him.  He wants discrete DHCP when the racks roll out individually and the ability to connect them all together for larger events without reconfiguration.

To me, the only way to accomplish this is to have a subnet in each cabinet with DHCP and a central router to route between the subnets.




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Scott AKA "Skyking" Holtzman

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Tom Bourke

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Re: Using a router as a switch
« Reply #22 on: November 10, 2014, 04:26:44 am »

No, that's not accurate.
From what I have seen in documentation on DHCP it is a first server to answer wins sort of protocol.  So you can have 2 DHCP servers on the same subnet if they hand out IP addresses from different ranges.

For the OP's configuration I would do similar to the following:
Rack 1:
Router IP 192.168.1.1
WLS units get static IP 192.168.1.11 to 19
Hand out DHCP 192.168.1.110 to 119

Rack 2:
Router IP 192.168.1.2
WLS units get static IP 192.168.1.21 to 29
Hand out DHCP 192.168.1.120 to 129

Rack 3:
Router IP 192.168.1.3
WLS units get static IP 192.168.1.31 to 39
Hand out DHCP 192.168.1.130 to 139

Also have a label listing addresses 192.168.1.200 to 250 as safe static IP addresses.

The router listed has auto uplink ports so just one cat5 rack to rack and plug the laptop into the most convenient rack.  Do not use the WAN port on any of the routers.

Having said all that, I think that having a "no network config necessary" is nice but not totally needed.  If a tech can't set an IP address on his or her laptop do you really want them to have access to your wls system?
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Re: Using a router as a switch
« Reply #22 on: November 10, 2014, 04:26:44 am »


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