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Subinterface for WAN connections - 2 ISPs - Cisco 1941 router

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Jul 7th, 2014
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I have  a Cisco 1941 router. I only have 2 Gig ports on it. I need to connect 2 ISPs. I know I can do subinterfaces on each port. The question is how do I connect the cables for the 2 ISPs once i create the subinterface.

Lets say I am going to use g0/1 interface and created g0/1.1 for ISP1 and g0/1.2 for ISP2. How do I connect the cables from ISPs' modems to the router?

Please help!

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Reza Sharifi Mon, 07/07/2014 - 09:28
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There is no way to do it directly unless you put a switch in front of the 1941.

So, lets say you have the switch

1-connect g0/1 from the 1941 to g0/1(switch)

2-configure the router with 2 sub-interfaces (2 and 3) with dot1q

3-switch g0/2 to ISP1 with dot1q (vlan 2)

4-switch g0/3 to ISP2 with dot1q (vlan 3)

You have to talk to both provides to make sure they will do dot1q on their side.

or

buy a second 1941 and connect each to a different provider.

HTH

 

Richard Burts Mon, 07/07/2014 - 09:35
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Reza

 

It seems to me that for 3) and 4) that the switch ports could be access ports that connect to the ISPs. Did I miss something that requires that they be dot1q trunk ports to the providers? Clearly dot1q is required to the router but why would it be required to the ISPs?

 

HTH

 

Rick

Reza Sharifi Mon, 07/07/2014 - 10:35
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Rick,

You are correct.  They could be just access ports. My apologies.

To the OP,

Al thought trunk to the ISP works, but it is simpler if you do access ports to ISPs.  This way, no coordination need it.

HTH

Reza Sharifi Tue, 07/08/2014 - 07:09
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for what device and what is the part number?

Pratik Prajapati Thu, 07/10/2014 - 07:53
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Cisco EHWIC-4ESG - 4-Port Gigabit Ethernet Enhanced High-Speed WAN Interface Card

 

Will this work? Can I use the Gig port on this for second WAN connection?

Richard Burts Thu, 07/10/2014 - 11:19
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I assume that this EHWIC is supported on your router and if so then you should be able to use it to make the connection to the second ISP. To do this I assume that you would want to configure a new vlan on the switch port and configure a vlan interface for the IP addressing for the second ISP.

 

HTH

 

Rick

Richard Burts Mon, 07/07/2014 - 09:31
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To achieve this you will need a layer 2 switch. You would configure at least two vlans on the switch. One vlan would be for ISP 1 and the second vlan would be for ISP 2. (you probably also want a vlan for management but this is not a requirement for the solution to work). One port of the switch would be configured as an access port in the first vlan and would physically connect to ISP 1. A second port of the switch would be configured as an access port in the second vlan and would physically connect to ISP 2. A third port of the switch would be configure as a trunk port, it would include both ISP vlans, and would physically connect to your router interface.

 

HTH

 

Rick

amukwazhe Mon, 08/03/2015 - 23:43
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Pratikjac

What solution did you apply for this issue. I need something exactly like your setup.

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