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How to join to local/seperate LAN's

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  • How to join to local/seperate LAN's

    I have two companies sharing office space. They each have their own Win/AD server running all but DHCP, this is handled at the router. They each have their own router and dedicated fiber connection. For "proprietary reasons"... the outgoing traffic for each company MUST remain separate; hence the two separate fiber lines into the building.
    The owners have come to us requesting that PC's on LAN A (192.168.xx.xx), be able to "see" server data on LAN B(10.0.xx.xx). I thought about RIP, but wasnt sure on the implementation, and there was a question about making sure LAN B's traffic moves OUT of LAN B's fiber. VPN came to mind, but again Im having trouble wrapping my head around flow control.
    Any thoughts would be great. If there is more info needed Ill be glad to provide that.

    LAN A runs off of a SonicWall TZ unit, LAN B runs off of an old Cisco unit that Im already planning to replace with a newer SonicWall unit.

    K.

  • #2
    Re: How to join to local/seperate LAN's

    All you're really doing is adding 1 new routing statement into LAN A's system to point to LAN B's subnet, and another statement in LAN B's router to point back to LAN A's subnet. While RIP may solve part of your issue, you've also got to think about DNS entries. Since each system is a separate entity, you'll have to put CNAME entries in LAN A's DNS system for LAN B's server names. Else, how do LAN A clients know what address to send packets to?

    As for which gateway is used to leave the building, the existing settings should suffice as long as you don't change the values handed out by the DHCP function. Adding a new routing statement at the router doesn't change anything with respect to default gateways, so clients' outbound traffic should still go where it always has.
    *RicklesP*
    MSCA (2003/XP), Security+, CCNA

    ** Remember: credit where credit is due, and reputation points as appropriate **

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    • #3
      Re: How to join to local/seperate LAN's

      I got to thinking, there is no real reason that these two LAN's NEED to be on separate subnets. The only REAL need, is that a certain group of machines exit the building through a particular gateway. Would it be plausible to either set up two WAN ports on the Sonicwall, and assign block of IPs to exit through one gateway, and another block to exit through another ? VLANs maybe ? Can VLANs talk to one another in the way I would need them to and still exit through assigned gateways ?

      K

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      • #4
        Re: How to join to local/seperate LAN's

        Think of VLANs as separate subnets. Your current setup already has 2 vlans, they just don't talk to each other (yet).

        If you want to combine things so that everyone's on the same subnet but use different gateways, then your 2 routers will both have to have a leg into this same subnet, and one group of clients should have their default gateways set to 1 ip, the other group to the second. But if you have contractual issues where one group is absolutely not allowed to send traffic out the other's gateway, the best way to guarantee that is to keep them as separate address spaces and route between them, as you originally planned. When you combine 2 different systems into one subnet, there's nothing to stop LAN B clients from getting addresses from LAN A's server's and vice versa. So guaranteeing that one set of clients isn't using the other set's gateway is nowhere near as simple.
        *RicklesP*
        MSCA (2003/XP), Security+, CCNA

        ** Remember: credit where credit is due, and reputation points as appropriate **

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