How to turn off (Disable) Multicast RPF Check (Needs forwarding Non-RPF Packets)

Discussion in 'Cisco' started by meteor713, Dec 5, 2004.

  1. meteor713

    meteor713 Guest

    I have two GRE tunnels connected with other vender's router.
    Multicast Packets come from the two GRE tunnels with same source IP.
    (It's been load-balanced network)

    monitor says "Tunnel 1 xxxxxx Not RPF packet..."
    So I added returning unicast static routing to two tunnels.
    The mcast packets from one of two tunnels forwarded OK.
    but the mcast packets from another tunnel is dropped by "RPF Check"

    Is there any way to turn off RPF check ?
    (There is no VLAN, nor same LAN mcast. so don't worry about looping)
    or any method to "RPF check" can see "two GW for same dst network"

    My config is as below.
    MCAST packet is "2.0.2.1 -> 239.255.12.42" only.

    Thanks!

    ---------------------------------------

    ip subnet-zero
    !
    ip multicast-routing
    !
    interface Tunnel0
    ip address 4.1.1.1 255.255.255.0
    ip pim sparse-dense-mode
    tunnel source FastEthernet0/1
    tunnel destination 5.1.1.211
    !
    interface Tunnel1
    ip address 4.1.2.1 255.255.255.0
    ip pim sparse-dense-mode
    tunnel source FastEthernet0/1
    tunnel destination 5.1.1.212
    !
    interface FastEthernet0/0
    ip address 3.0.1.1 255.255.255.0
    ip pim sparse-dense-mode
    ip igmp static-group 239.255.12.42 -> this is static MCAST IP
    no ip mroute-cache
    duplex auto
    speed auto
    !
    interface FastEthernet0/1
    ip address 5.1.1.200 255.255.255.0
    no ip mroute-cache
    duplex auto
    speed auto
    !
    ip classless
    ip route 0.0.0.0 0.0.0.0 30.0.1.101
    ip route 2.0.2.0 255.255.255.0 Tunnel0
    ip route 2.0.2.0 255.255.255.0 Tunnel1
    !
     
    meteor713, Dec 5, 2004
    #1
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  2. The global command "ip multicast multipath" might help you out,
    although, it is only effective for (s,g)-routes (I believe) and if the
    routes have the same cost.
    Igi.
     
    =?ISO-8859-1?Q?Ignaz_Kr=E4henmann?=, Dec 5, 2004
    #2
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  3. meteor713

    Hansang Bae Guest


    I don't think you can turn it off but you can fake it with "ip mroute"
    command. Not "ip route" but "ip mroute" It's safer since it can't be
    redistributed etc. It's a kludge, but you really have two choices if
    you *have* to overcome RPF. Add a secondary address in the same range
    as the S or use a static mroute.

    --

    hsb

    "Somehow I imagined this experience would be more rewarding" Calvin
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    Hansang Bae, Dec 6, 2004
    #3
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