Cisco comcast modem

Cisco comcast modem DEFAULT

So my boss wants our public wifi to be from just a regular comcast cable connection instead of just off a separate vlan on our network. Skipping past all the things that is annoying about this i need some technical guidance. i setup this network, and we are on a comcast WAN. so one port in my router is the uplink, which i created vlan1 from. now.. once the cable modem is hooked up, im not real sure what to do. use another port as a different uplink and create a separate vlan? for example i would want to use 10.1.105.x for the public wifi, comcast router addresses.


Best Answer

_Wizkid_

Datil

OP

Ohh, I didn't realize you were wanting to use 2 SSID's on one system, one being private one being public.

Yeah, I'd say that would be difficult if not impossible. Its over my head for sure. I thought the AP's were only for public wifi, not trying to use it for both.

We have WiFi here, but I have a separate internet connection and none of it is internal, it is all on a secondary internet connection, no LAN/Intranet access on it.

View this "Best Answer" in the replies below »

34 Replies

· · ·

Derek8923

Anaheim

OP

there are several switches after the router. main objective is have one AP that broadcasts public and private ssid's from two separate sources.

0

· · ·

TagYourIT

Tabasco

OP

my comcast cisco box is hardcoded to 192.168.254.x for LAN.. You sure you can use 10.1.105.x?

0

· · ·

dancrane

Habanero

OP

Are you trying to bind the SSIDs to different gateways, or is it acceptable to have a public VLAN with the gateway pointed to the comcast connection?

We'll probably what to know the model of router(firewall?) and AP you're using to give more detailed feedback.

0

· · ·

Derek8923

Anaheim

OP

For internal and private wifi we have a comcast fiber connection coming in to a cisco 3560 port that i have assigned an ip to. on that same 3560 i would like to have the comcast cable modem also plugged into a different port creating a separate vlan that the public wifi would use. these are all meraki ap's

0

· · ·

_Wizkid_

Datil

OP

You have correctly assigned the WAN port to the modem connection.

Now you need to use another NIC on the router to create a LAN connection.

Decide on your subnet and assign those addresses to the LAN port. So say your LAN for your Meraki AP's is 192.168.1.0/24, create that subnet and DHCP to the LAN port from the router. Then plug all off the Meraki's into a switch/switches that are going to that LAN port on the router.

Then you will route all traffic from the LAN port to the WAN port on that router.

0

· · ·

Derek8923

Anaheim

OP

my current WAN is setup like so on the 3560

interface GigabitEthernet0/24
description upling to Comcast WAN
no switchport
ip address 172.22.255.105 255.255.255.0
speed 100
duplex full
no keepalive

How would i configure the one for the comcast cable modem, if the ip of the comcast cable gateway is 10.1.105.1? like this or something different?

interface GigabitEthernet0/23
description upling to Comcast Cable
no switchport
ip address 10.1.105.1 255.255.255.0
speed 100
duplex full
no keepalive

interface Vlan105
ip address 10.1.105.1 255.255.255.0


0

· · ·

_Wizkid_

Datil

OP

Does your Comcast have a static IP? If not, then I would change it from ip address 10.1.105.1 to dhcp so it pulls it.

Do you have another, unused ethernet interface on the router? If so, use that for the public WiFi LAN. Then simply route

HOWEVER,

What I would do, if possible, is just completely segregate it. Use a different router, firewall, or something of the sort and then just take all of the existing Meraki connections and move it to a switch that is only used for WiFi.

If your boss wants them separated, then have them physically separated if at all possible, looks better from a security standpoint and makes it easier to accomplish.

0

· · ·

Derek8923

Anaheim

OP

i think the cable modem does have a static address. i assumed otherwise. ive assigned the ip of that router to a port on the cisco 3560, but now im not sure where to go as far as creating another vlan that points to that port

0

· · ·

dancrane

Habanero

OP

Shouldn't be too bad. I thought for a second you were being told to do some kind of hideous setup. 

As long as you can set the proper networking stuff and VLAN tag in the meraki, you should be able to route the traffic on that VLAN to the comcast cable WAN interface you're plugging in.

99% sure you've got the right idea, but I don't get to play with nice stuff, so we'll have to wait for some of the cisco pros to come by and help out with the actual CLI config stuff you'll need to do.

0

· · ·

Space Force

Habanero

OP

Derek8923 wrote:

there are several switches after the router. main objective is have one AP that broadcasts public and private ssid's from two separate sources.

Well technically the source is the same.  Private connections use the same Comcast connection as public, just being routed differently.  I don't see the benefit of having the public SSID using the Comcast modem direct and the private SSID use the router and then the Comcast modem.  Setup a VLAN and enable isolation on the public SSID so no one can talk to each other and be done.

0

· · ·

Derek8923

Anaheim

OP

that would be great, but thats not what i was told to do. i tried selling that idea since meraki has a built in isolated DHCP. but this is how it was requested. im just not certain on how to setup the routing of it all.

0

· · ·

Space Force

Habanero

OP

Derek8923 wrote:

that would be great, but thats not what i was told to do. i tried selling that idea since meraki has a built in isolated DHCP. but this is how it was requested. im just not certain on how to setup the routing of it all.

Thing is you'd still need a VLAN to make this work and jump through a lot of extra hoops to make it happen. It makes no sense. I hear what your being told, but I would explain either way your doing a VLAN and do you want to possibly spend more money to make this work or use what is already built in that designed for this purpose and spend no money.

0

· · ·

_Wizkid_

Datil

OP

Hopefully this helps. Cable modem goes from its ethernet port out to the Cisco router, say gigabit ethernet 0/1. Then, you have GigEthernet 0/2 for the LAN. Then route all outbound traffic coming from GE0/2 to GE0/1. If you were to plug a laptop into GE0/2 at that point, you should get to the internet on that port.

Now, you want to give all of the Meraki AP's access to that internet connection. So bring an ethernet cable over from GE0/2 and plug it into a switchport on the Cisco switch. Give it a VLAN, VLAN22 in my example. Then, everything else that needs to access the Comcast internet will need to be assigned to the same VLAN22 on the other switchports. So all of those AP's I drew in the example will need to be on VLAN22 and they will make their way from the Cisco switch to GE0/2 on the Cisco router and out to the Comcast WAN via GE0/1.

Does that make sense/help?


0

· · ·

Derek8923

Anaheim

OP

Yeah that makes sense and is pretty much how its setup now. The issue im having is, the cable modem is the second incoming connection. I have comcast fiber coming in on port 24. The issue im having is configuring the 2nd incoming connection of the cable modem to be its own vlan.

0

· · ·

_Wizkid_

Datil

OP

Derek8923 wrote:

Yeah that makes sense and is pretty much how its setup now. The issue im having is, the cable modem is the second incoming connection. I have comcast fiber coming in on port 24. The issue im having is configuring the 2nd incoming connection of the cable modem to be its own vlan.

So let me make sure I understand your entire setup correctly.

1: Are you connecting your Comcast modem to a physical interface on the router?

2: Why are you setting a different VLAN on the Comcast modem itself? And does your modem have two interfaces or just one? I would only worry about having a VLAN set on the switch and then routing traffic from the dedicated LAN interface to the dedicated Comcast WAN interface and calling it good.

0

· · ·

Derek8923

Anaheim

OP

Yes. It's a normal Cisco router with one interface being fiber and another being fiber. And I'm not trying to setup a vlan on the modem, I'm trying to get the data coming from the cable modem into the router on it's own vlan for public Wi-Fi. I'm just getting hung up on the routing part of it inside the router.

0

· · ·

Derek8923

Anaheim

OP

Yes I have fiber coming into one port and cable into another. I'm not setting a separate vlan the modem, I want the data from the cable modem to be on it's own vlan for public Wi-Fi. Where I'm getting hung up is the routing of the Comcast cable modem in the Cisco router.

1

· · ·

_Wizkid_

Datil

OP

Derek8923 wrote:

Yes I have fiber coming into one port and cable into another. I'm not setting a separate vlan the modem, I want the data from the cable modem to be on it's own vlan for public Wi-Fi. Where I'm getting hung up is the routing of the Comcast cable modem in the Cisco router.
Ok, I'm starting to grasp where your issues lie.I am thinking you need to have two different subnets. If you currently have routing setup like this:

Text

ip route 0.0.0.0 0.0.0.0 1.1.1.1(whatever your WAN IP is currently)

Then you may need to break it up. So say you use 172.16.1.0 255.255.255.0 for your internal network and you decide to use 192.168.1.0 255.255.255.0 for the public WiFi Lan.

Then you would probably 2 routes.

Text

ip route 172.16.1.0 255.255.255.0 1.1.1.1 (again, your primary WAN IP) ip route 192.168.1.0 255.255.255.0 2.2.2.2 (the IP of your Comcast WAN)

That's how I would start, not a guarantee, but where I would start.

0

· · ·

_Wizkid_

Datil

OP

· · ·

Derek8923

Anaheim

OP

Not today, i got hung up with some outages. Im hoping to get on this later today or tomorrow. Appreciate your assistance.

1

· · ·

Derek8923

Anaheim

OP

Sorry it took me so long to get back, I had a lot of stuff go on between then and now. But i was playing with this today... and i was thinking along the same as you with adding the IP route but i get an error that its an invalid route since its this router. I assigned an IP address to the switchport that the comcast cable modem is plugged into and made the route ip route 10.1.105.0 255.255.255.0 10.255.105.1    10.255.105.1 being the ip address of that switchport.

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· · ·

_Wizkid_

Datil

OP

Is 10.1.105.0/24 (255.255.255.0) the network you are deploying the Access Points on?

0

· · ·

Derek8923

Anaheim

OP

Its one of the SSID's on the AP's. the other ssid is the private internal. im starting to question if this is even possible.

0

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Sours: https://community.spiceworks.com/topic/1985915-comcast-public-through-cisco-router

Configuring the Comcast Cisco DPC3939B / DPC3941B Gateway

The ideal network involves your Internet Service Provider (ISP) connecting onsite to a standalone modem that connects to a router, preferably a router recommended by Nextiva. If you have more devices on your network than ports on your router, you can connect a switch to your router to expand the number of ports.

There are five main areas that you should be concerned with regarding your network. They are:

SIP ALG:  Nextiva uses port 5062 to bypass SIP ALG, however, having this disabled is always recommended. SIP ALG inspects and modifies SIP traffic in unexpected ways causing one-way audio, deregistrations, random error messages when dialing and calls going to voicemail for no reason.

Double NAT: When routing SIP Packets, the packet will come into the modem, and be directed to a private IP address (the router). When the SIP packet goes into the router, it is given another private IP address. This SIP packet, intended for a specific destination, will no longer know where to go, causing one-way audio, dropped calls, deregistrations, and failed transfers among others.

Multicasting: When a call comes into a Call Group and simultaneously rings all phones, the Internet traffic of the internal network spikes. Without multicasting enabled, you can have what’s called “port collisions”. Basically, data coming into the network is sent out to all devices on the network. Since all phones are likely using port 5062, the data spike causes packets to be dropped. This can cause failed transfers, dead air upon call retrieval, among other issues.

DNS Server Configuration: If the DNS server being used is not up to date and consistent, devices (Poly phones in particular) can become deregistered. Nextiva always recommends using the Google DNS servers of 8.8.8.8 and 8.8.4.4.

Firewall Access Rules: The simplest way to ensure that traffic is not being blocked is to allow all traffic to and from 208.73.144.0/21 and 208.89.108.0/22. This range covers the IP addresses from 208.73.144.0 – 208.73.151.255, and 208.89.108.0 – 208.89.111.255.


The Cisco DPC3941B Comcast Gateway is a Business Wireless Gateway often given to Comcast Business customers for their Internet service. This equipment, by itself, is not recommended for use with VoIP service. Common issues include one-way audio, dropped calls, failed transfers and deregistrations, among others.

The NAT feature may be disabled by default and will need to be enabled, and DNS servers need to be configured to a dependable set of DNS servers (Nextiva recommends Google DNS). This setting is only configurable on the DPC3941B

While there are limited options that can temporarily alleviate some of the above symptoms, for a permanent solution, this Gateway will need to be put into “Bridge Mode” and connected to a recommended firewall or router to provide quality audio.  


To Enable NAT and Configure DNS Servers: 

NOTE: The login address and credentials below are the default when the Gateway is shipped and can be modified by your Network Administrator. If the default credentials are not being accepted, speak with the Network Administrator who set up the network. 

  1. As a Network Administrator, log into the Cisco DPC3939B/3941B Gateway by opening a web browser on a device connected directly to the Gateway and going to http://10.1.10.1.
  2. Enter the following credentials to log in:
  • Username: cusadmin
  • Password: highspeed or CantTouchThis
  1. Navigate to Gateway > Connection > Local IP Network.
  2. Check the Assign DNS Manually and enter the following information:
  • Primary DNS Server: 8.8.8.8
  • Secondary DNS Server: 8.8.4.4
  1. Click Save Settings.

For DPC3941B Only: 

  1. Navigate to Advanced > NAT.
  2. Uncheck the Disable All checkbox if there is a checkmark in the box.
  3. Reboot the router and any devices connected to the router.

Was this article helpful?

Sours: https://www.nextiva.com/support/articles/comcast-cisco-dpc3941b-gateway.html
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Network issues with new Comcast modem connecting to a switch and switch connecting to Cisco PIX 506E router

We have a pretty simple network in our office. There are two small switches, a Cisco PIX 506E router and internet connection is provided by Comcast's modem/router. Please see diagram (network connection scheme). We used to have two working logical (private) networks, i.e. 10.1.10.x and 192.168.0.x. In the 10.1.10.x net, we have 5 IP’s and the gateway is 10.1.10.1 (the Comcast router). And they are mapped by NAT on the Comcast router since we have 5 public IPs given by Comcast. So for example, it's 50.197.10.x mapped to 10.1.10.x

For the 192.168.0.x net, the NAT is performed by a Cisco PIX 506E firewall. The connection scheme is such that the Ethernet cable from the Comcast router is connected to a switch (switch 1) and a cable from the switch (switch 1) is connected to the Cisco PIX router. This setup worked great for many years. Internet, VPN for remote workers, and all the 10.1.10.x IPs were reachable from outside via our public IPs.

A few weeks ago, we lost internet connection and basically nothing worked. Comcast technician came and changed the modem which is a "new" model.

But things do not work well as before. Internet becomes flaky, i.e. web pages load very slowly, VNP does not work, speedtest will fail to run or get slow download and no upload. Then I tried connecting the modem output directly to Cisco Pix, then we have internet as well as VPN working well but the public IPs are not reachable, i.e. from outside, we cannot access 50.197.10.x and from inside our network, we cannot access 10.1.10.x.

Someone suggested that about 2 years ago, Comcast changed their modem design such that you can only connect the modem directly to a router i.e. our original connections scheme is not supported anymore. But the Comcast technician denied that and he said the problem could be a bad switch. So I went ahead changed the 2 switches by putting in 2 new switches. Still the problems persist. Since my switches and Cisco PIX appears to be working just fine, I suspect there is some kind of compatibility or configuration issue in the Comcast modem. It is clear that if I go back to the original connection scheme (see diagram), I cannot get a stable connection. If I connect the Ethernet cable from Comcast modem directly to the Cisco PIX, I get stable internet connection, but I will lose access to my five public IPs which I need for a few applications. How can I make it work as before?

Please help. network connection scheme

Sours: https://superuser.com/questions/1635086/network-issues-with-new-comcast-modem-connecting-to-a-switch-and-switch-connecti
Connect Cisco Router \u0026 Switch to ISP Home Router and Access Internet

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Connect Cisco Router \u0026 Switch to ISP Home Router and Access Internet

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