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One Modem Connected Via Switch to Two Routers (Directly)

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Contributor

One Modem Connected Via Switch to Two Routers (Directly)

I have a case where I want as close to zero failure rate as Comcast can possibly allow.  Therefore, I want the following:

1.  Cable connected to modem

2.  Modem connected to switch

3.  Two routers connected to switch

4.  Multiple computers connected to either routher.

5.  In some cases one computer may be connected to 2 routers (2 NICs).

 

I DO NOT want router 2 connected to router 1 connected to modem since if router 1 goes down I have a point of failure for both routers.

 

Can comcast do this?  If so, do they charge extra for extra public IP address?

 

Expert

Re: One Modem Connected Via Switch to Two Routers (Directly)

You would need additional public IP addresses assigned from Comcast in order to hang an ethernet switch directly off of a straight cable modem. You only get one public IP. Some areas still offer additional dynamic public IP's, some don't. Call in to Customer Service to inquire. They used to call it an "IP pack". There is an additional fee.



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Contributor

Re: One Modem Connected Via Switch to Two Routers (Directly)

So far I have talked to 5 reps at comcast with no luck

Contributor

Re: One Modem Connected Via Switch to Two Routers (Directly)

In any event, nobody even at Tier 3 knows what I'm talking about or if they do they don't know the answer.  I asked customer service about paying for multiple addresses (they had no clue, even after re-phrasing the question 5 different ways).  So, I'd be happy to pay for the address, but I need the "magic" words to tell CS what I want.

Expert

Re: One Modem Connected Via Switch to Two Routers (Directly)

Perhaps it is not offered in your area ? Try asking for a manager.



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We ask that you post publicly so people with similar questions may benefit from the conversation.

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Contributor

Re: One Modem Connected Via Switch to Two Routers (Directly)

After speaking to 7 reps I was told it couldn't be done.  The last rep called me back and said that it could, and she set it up for $4.95/mo.

Authorized Vendor

Re: One Modem Connected Via Switch to Two Routers (Directly)


Ken98045 wrote:

After speaking to 7 reps I was told it couldn't be done.  The last rep called me back and said that it could, and she set it up for $4.95/mo.


That is what I pay for the same thing..  That is not a normal setup so it takes more to get that setup..

-------------------------------------
Network Engineer, IP Engineer, Docsis..; the views expressed on this post are mine and do not necessarily reflect the views of my employer..

Gamer.. Living the dream one catastrophe at a time Smiley Happy ..
Frequent Visitor

Re: One Modem Connected Via Switch to Two Routers (Directly)

I am very to have found this thread. I have exactly the same home network configuration and also want to connect [at least] 2 routers to my modem with a switch in between. In the hopes of avoiding having to talk with 7 Comcast reps. can you please tell me exactly what i should ask for? And should I ask to speak with a manager when I place the call? I will probably need some advice on how to route the specific ip addresses I am given through the switch and to the correct router. I live in the Minneapolis, Minnesota area. Thank you in advance.

Authorized Vendor

Re: One Modem Connected Via Switch to Two Routers (Directly)

I know EG is going to ask so, on my next discussion with Comcast I will ask about this and how we can make this a little easier for customers..  Right now it is random to get the correct person to get this working..

-------------------------------------
Network Engineer, IP Engineer, Docsis..; the views expressed on this post are mine and do not necessarily reflect the views of my employer..

Gamer.. Living the dream one catastrophe at a time Smiley Happy ..
Contributor

Re: One Modem Connected Via Switch to Two Routers (Directly)

I had to talk to Tier 3 technical support.  You just need to keep asking.  When they ask you what brand switch or router you have then you know you are talking to the wrong person.  If they don't understand what you are asking for you have the wrong person.  If you can feel their eyes glazing over.... I never did find the right "magic" words to describe to a rep what I wanted. Something like the "Extended IP Addressing Plan" would be nice, but if there is I didn't find it.

 

I'd suggest calling on a weekday if possible.  It seems to me that the more proficient reps work M-F.

 

It may not be available in every area, but I'm willing to bet that if you keep pushing you can find the right rep.  BTW, the Tier 3 rep was able to make the change to my account instantly (with a confirmation text message OK).  Try very hard to prevent them from transfering you back to Customer Service/Sales once you find someone who can understand what you want.

 

Eventually the modem was reset, and everything just worked.  After about 50 minutes of the run around....

 

 

I believe that while 1 additional IP address is $5, they have a package of 4 for $10 (at least I was told that once).

Authorized Vendor

Re: One Modem Connected Via Switch to Two Routers (Directly)

I just checked and on my bill it looks like this:

 

Additional services and equipment

  • Internet
    Additional IP Addresses  9.95
    (up to 4)
-------------------------------------
Network Engineer, IP Engineer, Docsis..; the views expressed on this post are mine and do not necessarily reflect the views of my employer..

Gamer.. Living the dream one catastrophe at a time Smiley Happy ..
Frequent Visitor

Re: One Modem Connected Via Switch to Two Routers (Directly)

Thank you very much for your assistance. After talking to a few Comcast reps. I was able to order (4) additional IPs for a total of $9.95/mo. They said it will take approximate (2) hours to make the change.

My current network configuration consists of (2) routers. Router-A is connected directly to my modem. Router-B is connected to Router-A. What I am trying to do is physically connect Router-A and Router-B directly to my modem so I can have (2) completely separate and independent networks. But since I only have (1) ethernet connection on the back of my modem I am going to connect a switch directly to my modem. Then connect both routers directly to the switch. Is this correct? Will an unmanaged switch work or do I need a managed switch? If managed, how should it be configured. Again,Thank You for your time and assistance.

Authorized Vendor

Re: One Modem Connected Via Switch to Two Routers (Directly)

Shameless Plug coming...

 

I use a SB8200 it has 2 Gig ports on it, with multi IP support you can use both ports with more then 1 IP..

 

SB8200 Port 1 --> Home Router

              Port 2 --> Switch port (VLAN setup)

                              Switch port 1  --> SB8200 port

                              Switch port 2  --> Home LAB Router

                              Switch port 3  --> Test LAB Router

                              Switch port 4 -->  Future setup Smiley Happy

-------------------------------------
Network Engineer, IP Engineer, Docsis..; the views expressed on this post are mine and do not necessarily reflect the views of my employer..

Gamer.. Living the dream one catastrophe at a time Smiley Happy ..
Authorized Vendor

Re: One Modem Connected Via Switch to Two Routers (Directly)


jrsy010718 wrote:
But since I only have (1) ethernet connection on the back of my modem I am going to connect a switch directly to my modem. Then connect both routers directly to the switch. Is this correct? Will an unmanaged switch work or do I need a managed switch? If managed, how should it be configured. Again,Thank You for your time and assistance.

You A ) need a modem with more then 1 port

B ) need a unmanaged switch with only internet ports on it  (or all devices will try and get a public IP)

C ) need a managed switch with a VLAN setup for internet ports..

 

-------------------------------------
Network Engineer, IP Engineer, Docsis..; the views expressed on this post are mine and do not necessarily reflect the views of my employer..

Gamer.. Living the dream one catastrophe at a time Smiley Happy ..
Frequent Visitor

Re: One Modem Connected Via Switch to Two Routers (Directly)

Thanks for the additional information but I'm not sure I understand. Are you saying I cannot just connect an unmanaged switch to the modem (SB6141, has 1 ethernet port) and then connect each router to the switch? 

Expert

Re: One Modem Connected Via Switch to Two Routers (Directly)


Ken98045 wrote:

After speaking to 7 reps I was told it couldn't be done.  The last rep called me back and said that it could, and she set it up for $4.95/mo.


Good to hear ! Sheeesh.... Sometimes it's like pulling teeth with the reps.....



I am not a Comcast Employee.
I am a fellow customer, volunteering my time to help other customers here in the Forums.
We ask that you post publicly so people with similar questions may benefit from the conversation.

Was your question answered? Mark the post as best answer!
Frequent Visitor

Re: One Modem Connected Via Switch to Two Routers (Directly)

Ken98045 : After you got your additional IP(s) from Comcast were you able to get your new network configuration setup the way you wanted to - ISP Modem -> switch -> routers? Or did you have to buy a modem with (2) eithernet ports (ie. SB8200) and go with the config suggested above? A managed switch with VLAN connected to one of the SB8200 ports and a router connected to the other SB8200 port? I really don't want to spend an additional $200 on a new modem....

Contributor

Re: One Modem Connected Via Switch to Two Routers (Directly)

Yes.  I attached a cheap gigabit switch directly to my old 1 port modem.  I then plugged each of 2 routers into the switch.  Both routers then "just worked". 

 

I did test it with 1 router and one computer first to remove unnecessary complications.  That "just worked" too.  In that case my old IP address was still assigned to the old router, and a new IP address was assigned to the computer.  I then removed the computer and plugged in the 2nd router.

 

BTW, my second router is now running (via Tomato) a VPN client.  So, if i want VPN I can connect to router 2, if I want speed router 1.   This can be done by connecting Router 2 to Router 1, but that does add a point of failure for Router 2.  I also want Router 2 to provide a failover for a computer running software on a computer with two NICs.

 

Contributor

Re: One Modem Connected Via Switch to Two Routers (Directly)

One question I have: Are the additional IP addresses static or are they subject to re-assignment via DHCP?  I believe that they are DHCP, but I don't know for sure.  I asked the rep I ordered the address from, and she wasn't sure either.

 

Frequent Visitor

Re: One Modem Connected Via Switch to Two Routers (Directly)

Ken98045: Thanks for getting back to me. We have very similar home network needs. I too have a VPN-only router that is currently connected to my Primary router (which connects directly to my 1-port modem). My plan is to move the VPN-only router off of the Primary router, which is used for gaming/streaming/general intenet access, and connect it directly to my modem. I was hoping to do that by just adding an unmanaged switch. That way I can keep both networks separate and independent of each other. In the above diagram it looked like I had to have a Managed switch to do that. I'm glad to hear that you were able to make your config work with just an unmanaged switch. I don't know much about networking as have been trying to learn how to make VLANs work via youtube videos if I had to. They don't look very complicated from what I have learned thus far. I also don't really see the need for them however. Going forward I want to be able to add a third router to my home network, a home-lab/test network. Now that I have the addtional 4 IPs from Comcast I think I should just be able to plug another router into the switch. I hope I'm not over simplifying this.... BTW, I'm planning on buying a simple 5 port unmanaged TP-Link switch - https://www.amazon.com/TP-Link-TL-SG1005D-Unmanaged-Gigabit-Desktop/dp/B000N99BBC/ref=pd_sbs_147_1?_... - is that what you are using? If for some reason I decide I need a managed switch I will probably go with this - https://www.amazon.com/TP-Link-Ethernet-Sheilded-Replacement-TL-SG105E/dp/B00N0OHEMA/ref=sr_1_2?ie=U... . You mentioned router fail-over. I haven't thought much about that. For what it's worth, I'm probably going to look into PFSense and learn more about networking in a (possibly) VM playground).

Expert

Re: One Modem Connected Via Switch to Two Routers (Directly)


Ken98045 wrote:

One question I have: Are the additional IP addresses static or are they subject to re-assignment via DHCP?  I believe that they are DHCP, but I don't know for sure.  I asked the rep I ordered the address from, and she wasn't sure either.

 


They are dynamically assigned. Only Business Class connections can get statically assigned public IP's.



I am not a Comcast Employee.
I am a fellow customer, volunteering my time to help other customers here in the Forums.
We ask that you post publicly so people with similar questions may benefit from the conversation.

Was your question answered? Mark the post as best answer!
Authorized Vendor

Re: One Modem Connected Via Switch to Two Routers (Directly)


jrsy010718 wrote:

Ken98045: Thanks for getting back to me. We have very similar home network needs.


Have fun with it.. Smiley Happy..

-------------------------------------
Network Engineer, IP Engineer, Docsis..; the views expressed on this post are mine and do not necessarily reflect the views of my employer..

Gamer.. Living the dream one catastrophe at a time Smiley Happy ..
Frequent Visitor

Re: One Modem Connected Via Switch to Two Routers (Directly)

My apology for not posting this sooner and letting you all know that I did get this to work. I was able to get a package of 4 additional IPs on my residential account. Had to go through a couple of Comcast reps. but finally did get to one that understood what i needed. I purchased a smart switch and placed it between my modem and my routers. At first only one of my routers (which was connected to port 1 on the switch) worked. So, I called Comcast Support and somehow while I was going thru their support menus I managed to active/re-active my account. Then my 2nd router, which is connected to port 2 on the switch, started working. So, all good. I was not able to use the Smart Configuration Utility to access the switch. TP-Link tech support said it is because the switch is on the WAN side of the routers. So, I changed the IP address of the switch to a WAN address and I was able to connect to it via WiFi. However, I didn't want my switch login screen exposed to the WAN so I changed it back to it's default LAN address. I have the switch setup like I want it and shouldn't need to directly connect to it often. When I do I will just use an ethernet cable. Note, when you do connect directly to the switch your client PC will need to have an address on the same subnet as the switch. Finally, I could have gotten by with an unmanaged switch and all of my additional IPs would have worked fine. The managed switch gives me the QoS options that I wanted. Thanks again to those who helped me Smiley Happy

Expert

Re: One Modem Connected Via Switch to Two Routers (Directly)

Happy surfing !



I am not a Comcast Employee.
I am a fellow customer, volunteering my time to help other customers here in the Forums.
We ask that you post publicly so people with similar questions may benefit from the conversation.

Was your question answered? Mark the post as best answer!