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understanding Routing Cisco vs. Linux



Currently, I am creating a simple Linux Router with CQB and Iptables. 

The machine I have only has 2 interfaces.

We have the following devices on our network:

1 Cisco Catalyst connecting 16 Class C Networks 
1 Cisco Router Routing packets to the inside

The Catalyst uses VLans for our entire network.

It appears that the Catalyst is doing routing for the virtual networks
as it should. But, I am scratching my head over how the Catalyst 
handles incoming and outgoing connections. 

Traffic seems to flow differently depending on
its direction. 

Do I need to worry about how the VLAN handles packets
when I install the Linux Router ?

Also does the following diagram look like it will work  ?

Currently the route is -> 

    Trunk
      |
    209.243.32.65 
      |
      |
      | 192.146.226.1 (Catalyst Routing of Vlans)
      [Catalyst] ---209.243.32.0/20 
                 ---192.146.226.0/24


I figure that this may work it is my first attempt at using iproute:

    Trunk
    |
    209.243.32.65
    |
    [Linux Router] 209.243.32.66 eth0
                   209.243.32.67 eth1

        ip route add 209.243.32.65 dev eth0              
        ip route add 192.146.226.1 dev eth1
        ip route add 192.146.226.0/24 dev eth1
        ip route add 209.243.33.0/24 dev eth1
        ip route add 209.243.34.0/24 dev eth1
        ...


    | 
    | 192.146.226.1 (Catalyst Internal Routing)
    [Catalyst] 
            ---209.243.32.0/20
            ---192.146.226.0/24

http://www.shorewall.net/traffic_shaping.htm



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