route and static route to a gateway

Discussion in 'Linux Networking' started by Sting, Feb 19, 2004.

  1. Sting

    Sting Guest

    Hello,
    from man route:
    gw GW route packets via a gateway. NOTE: The specified gateway must
    be reachable first. This usually means that you have to set up a
    static route to the gateway beforehand.

    What is static route to the gateway ?
    How do you set it ?

    regards,
    sting
     
    Sting, Feb 19, 2004
    #1
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  2. Sting

    MM Guest

    If your gw isn't connected directly to you you must specify with route
    program itself what other machine are from you to gw. If a direct
    connection exists you don't do anything.
     
    MM, Feb 19, 2004
    #2
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  3. It depends whether the gateway is already defined in a route for that
    interface (like a local network route). If not, you would typically set a
    -host route to gateway IP before using it as a default route. With things
    like ppp or pppoe, a route to the gateway (remote ppp IP) is usually
    automatic and defaultroute option would set the default route.

    It is usually only a concern when doing some sort of special static
    networking, like using an IP from 1 network on another interface. For
    example:

    Router-192.168.1.1-----eth0/eth1-----192.168.1.0/255.255.255.0 network
    where eth0 192.168.1.2 netmask 255.255.255.255
    eth1 192.168.1.3 netmask 255.255.255.0

    In this case bringing up eth1 from scripts would usually automatically set
    a local router on eth1 for 192.168.1.0/255.255.255.0 network, but eth0
    would have no route. So somewhere you would need to:

    route add -host 192.168.1.1 dev eth0
    route add default 192.168.1.1 dev eth0

    However, for the router set for 192.168.1.1 netmask 255.255.255.0 to
    see the rest of that network without having a gateway set for it, besides
    enabling ip_forward, proxy arp would have to be enabled for eth0:

    echo 1 > /proc/sys/net/ipv4/conf/eth0/proxy_arp

    Then eth0 would answer arp requests from the router for any IPs on eth1.
     
    David Efflandt, Feb 21, 2004
    #3
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