[CentOS] CentOS 6 - VM network bridge issue

[James Hogarth]

> I built a CentOS 6 machine to host several CentOS 6 guest servers. As all
guests will be Internet facing I set up the host with two bridged NICs and
assigned an Internet facing IP address to br0 and a local IP address to br1.
>
> Each guest was installed using br0 and br1 with virtio drivers.  On each I
assigned an Internet facing IP address to eth0 and a local IP address on
eth1.  So far so good.  I can access the guest servers from either IP
address as expected.  That is HTTP, SSH and SMTP servers on them are
accessible and do what they are supposed to do.
>
> Except...  Except from any location outside of my Comcast Cable Modem.  To
be clear, from any machine inside the modem to any address on the guests,
all works perfectly.  But outside the modem the guest apps either don't
receive packets or for some reason don't respond, and I've tired it from
four different locations.
>
> Using Wireshark on the guests I can see the packets arrive from the
outside sources, but no response is seen.  On accesses from inside I can see
both incoming and outgoing packets, as expected.
>
> I can ping the outside sources from the guests, yet pings from the outside
sources get no response from the guests.  All the outside sources get
responses when pinging the host.  I can ping the guests from any inside
machine.
>

Initial thought is a routing issue particularly with multiple NICs.

What does 'ip r s' reveal?
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