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Can a Cisco 1720 router support two separate networks and share a dsl internet connection?

Posted on 2004-11-01
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Last Modified: 2008-01-09
My network is currently using a simple dlink dsl router for internet connectivity.  I need two subnets and I need them to use the same dsl connection for internet access.  I have a win 2k domain with 24  clients.  I have a 1720 router.  What kind of WAN connection do I need? (Do I have to have an ADSL WIC card or will something else work?) Can I use an ethernet card in one of the WIC slots so that I can connect a second network?  Help.
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Question by:DaleFrazier
    12 Comments
     
    LVL 13

    Assisted Solution

    by:td_miles
    You can quite easily add an ADSL WIC and a 2nd Ethernet WIC to allow you to have a router that has 2 ethernet ports & an ASDSL port.

    If you want to keep the network seperate, just make sure you setup ACL's to prevent the traffic from each ethernet network from going to the other one.

    If the two subnets share the same physical network (ie. plugged into the same switches), then you don't even need a second NIC, you can add a 2nd IP address to the existing ethernet interface of the router.
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    LVL 8

    Assisted Solution

    by:MarkDozier
    not a bad ideal td. but if he has a managed swicth he can create 2 vlans to serperate the subnets and  only need one ethernet and one  xDSL WIC for the 1720.
    You can see there is more then one way to skin a cat.
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    LVL 79

    Assisted Solution

    by:lrmoore
    If they have a DSL modem already that hands off Ethernet, how about creating 3 VLAN's with 3 subinterfaces on the router? Not the most secure by any means, but it's an option if each of the two other networks have their own firewall...
    A single FastEthernet port for a "router-on-a-stick"
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    Author Comment

    by:DaleFrazier
    All computers are currently on the same network.  I want to set up a test lab that will be separate from the production network.  If I screw up something on the test lab I don't want it to affect the production network.  I am trying to do this on a limited budget.

    A few questions:

    Will the cisco 1720 support VLANs?  If yes wouldn't I need switches that also supported VLANs?  I do not have this.  Currently I have 1 hub and 1 cisco 1912  switch that does not support VLANs (standard ed.).

    I currently have a modem attached to my dsl router WAN port.  What would my modem attach to on the 1720, I assume a ENET WIC?  Thanks for your help.
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    LVL 79

    Assisted Solution

    by:lrmoore
    Yes, the 1720 supports vlans, but the switch would also have to support them. Having one without the other is not an option.
    Yes, the DSL modem would connect to an Ethernet WIC.
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    Author Comment

    by:DaleFrazier
    I just looked at a router on ebay that claims to have dsl/cable connectivity but it only has a DSU T1 WIC.  How is this possible?  I have seen this more than once.  I am confused?  My 1720 has a dsu t1 wic.  If I need to buy a card, do I buy a enet wic or a adsl wic?  which is cheaper and which is easier to setup.  Thanks.
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    LVL 79

    Accepted Solution

    by:
    It is not possible to connect dsl/cable to a T1 WIC.
    You need either a ADSL WIC, or a WIC1E Ethernet. Ethernet is by far the easiest to setup and will work with either cable or dsl, it's also cheaper.

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    Author Comment

    by:DaleFrazier
    I can get a WIC1E from another company for free.  The only problem is that it is 10baseT.  Is this enough bandwidth for a WAN connection supporting 24 users?  Users regularly connect to the internet mostly for email and surfing.  I sometimes use this connection to download updates for the computers on the network.  Also is a WIC1E the same as a WIC ENET?
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    LVL 79

    Assisted Solution

    by:lrmoore
    Yes, WIC1E = WIC ENET
    10Mb is plenty because your broadband is only what - 3Mb max?
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    Expert Comment

    by:mottie
    1720 does NOT support VLANs (I know this because I have one)

    "The Cisco 1721 offers many significant feature enhancements over the Cisco 1720 router, including: greater memory architecture, faster processing, and 802.1Q VLAN support."

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    Expert Comment

    by:Currysan
    I am attempting to set up two VLANS on a Cisco 2924xl and have a Cisco 1720 router.  I can only bring one VLAN up at a time.  How can I use this single interface to feed both VLANS.  My router doesnt seam to have subinterface capabilities.  Am I simply two sheets to the wind?
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    Expert Comment

    by:mottie
    As far as I know you're going to have to either purchase another interface, or buy a different router. It may be possible if you have enough flash/memory, but I know 802.1Q is not supported on my 1720 with the basic feature set.
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