2 WAN, 1 LAN, keep connectivity

I Have 2 internet connections coming in , 1 business/ static IP Cisco 851 router, another one residentioan dynamic IP cable modem,
I have a LAN of 6 computers which I would like to connect to the 2 incoming connections. I want to keep the integrity of the LAN (all PC continue to share files/printers) but individual static / dynamic IP's need to be assigned to specific computers.
I already know how to do this by BREAKING UP my LAN. But I am convinced there must be creative ways to do it without breaking it up.
For instance , there are routers with 2 WAN inputs, Or perhaps 2 LANS could be created, each for its own WAN, and then bridge the 2 LANs somehow to allow file access accross LANs?
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  1. The IP addresses that need to be statically assigned are the main question here.
    The "business" LAN IP addresses the Cisco is using will determine your numbering.

    Are the static IP's in a range where only the last group of numbers are different?
    example: 192.168.1.xxx

    If so, the the dynamic IP's could be set to a group of numbers in that range that
    will not conflict with the static addresses.
    example: >

    The LAN IP of the residential router could be changed to the same scheme.
    example: static

    Only one router should be running the DHCP server option. Preferably the Cisco.
    Assign appropriate Gateway and DNS addresses (static or DHCP) to each computer for internet access.
  2. Connect a cable from Router 1 to Router 2 using the LAN ports. Your modem cables will go to the WAN ports. Assign different numbers for the LAN settings for each router. Router 1 will be (exam.) and Router 2 will be Use these two numbers as your gateways to internet. Turn off the DHCP on router 2. Use static addresses for the computers connected to router 2 (exam. xxx.xxx.x.3 thru 10). On router 1, Use DHCP or DHCP/static where the same ip is assigned to the same mac address consistently (exam. xxx.xxx.x.12-3). Try that see if it works.
  3. The static IP's are something like 98.58 122.16x,
    _._._.160 is the assigned subnet
    _._._.161 is the gateway,
    _._._.162 thru 166 are my available IP's
    and is the mask,
    and _._._.167 is not available bacause it is used internally by the ISP for some other housekeeping.

    I would then have 5 computers getting 5 static IP's, going to an 8 port switch, and then going into the CISCO router. These are working right now.

    Then 1 computer going to router 2, WAN to DHCP cable modem.

    On router 1, Use DHCP or DHCP/static

    I cannot configure the CISCO, it's a black box to me.
    The ISP won't provide the admin password, and only they can administer it, remotely. (kind of makes sense).

    Now if I really needed access to manage the router on line1, I suppose I could insert another router between the CISCO and my LAN, and use this downstream router as the bridge point to LAN2.
    If I did that, I would end up with a Linksys BEFSR41 as my configurable router on Line1, and this router does not have an option like "DHCP/static ".
    I can only enable or disable DHCP.
    Maybe you mean, enable DHCP, and then
    for "WAN connection type" select "Static IP", providing for the
    WAN IP address, one of my 5 static IPs.

    ( I knew a router would eat up one of these)

    Then, 4 of the static IP machines would get their own IP, and get the CISCO as gateway, looking thru the Linksys as if it were transparent (is that possible?).
    The 5th static machine would get a private IP from the Linksys, use the Linskys as its gateway, and wear the linksys WAN IP while surfing the web, but not be direcly reachable from the web, bacuse the Linksys obscures it.

    Am I getting this right?
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