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i can ping and ssh into instance with private ip and floating ip
instance can ping the control node ip, but cannot ping the compute node and
any external network

i have installed quantum in the control node host, and it only got 1 nic
(same as compute node), and use eth0:0 and eth0:1 to vitualize 2 other nic
(eth0:0 on compute node)

i use tcpdump on control node and compute node to monitor package from
instance, actually compute node will reply the icmp package but with
destination of instance private ip, since compute node has no route to that
network, it failed and no package receive on control node nic. but when i
add route via control node, it can reply to insance as expected
then i use tcpdump on control node and instance to monitor package to the
floating ip, instance got nothing but control node captured the package and
reply it instead of instance

so i think the problem may be that the control node will not modify the
source ip when forwad the icmp package, more exactly, the nat functionality
is not enabled?

and i try some other command such as "iptables -t nat -A POSTROUTING -o
eth0 -j MASQUERADE" but it is not working

i'll paste some output if anyone needs
thanks
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