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From "Milamber (JIRA)" <>
Subject [jira] [Created] (CLOUDSTACK-9770) Virtual router / Network regression since with public interface eth2
Date Thu, 02 Feb 2017 18:59:51 GMT
Milamber created CLOUDSTACK-9770:

             Summary: Virtual router / Network regression since with public interface
                 Key: CLOUDSTACK-9770
             Project: CloudStack
          Issue Type: Bug
      Security Level: Public (Anyone can view this level - this is the default.)
          Components: Virtual Router
    Affects Versions:,,
         Environment: CloudStack with advanced network installation
            Reporter: Milamber
            Priority: Critical
             Fix For: Future

I found a (possible) bug introduce by CLOUDSTACK-9339 [1] (Pull Request PR1659 [2]) on CloudStack
Advanced network installation.

Since this changes (9339), the public network's route on eth2 (public interface) in VR is

Before on VR, we have sometimes like:

ip route show table Table_eth2 dev eth2  table Table_eth2  scope link
default via dev eth2

where is the public network and the default gateway.

After with the ip route command shows only:
default via dev eth2  proto static
throw  proto static
throw  proto static

(missing route for public network)

The changes 9339 introduce the iptables connmark to add 0x2 mark on ip packets from internal
VMs IP and an ip rule to use the Table_eth2 network table for these ip packets.
So if another machine into the public network try to reach a virtual machine inside CloudStack
using their public IP, the packets's travel is:
source_machine--> VR (de-NAT) --> VM_inside_CS --> VR (NAT+using Table_eth2) -->
default_public_gateway --> source machine

The issue is if the default_public_gateway refuse to forward IP packets with the source IP
and destination IP in the same network (often when the gateway is a firewall), then the connection
between a machine into public network is not possible with all VM behind the CS virtual router.

The correct network path for the packet must be:
source_machine--> VR (de-nat) --> VM_inside_CS --> VR (NAT+using Table_eth2) -->
source machine (directly because on public network)

To fix the issue (workaround), just execute this command on the virtual router:
 ip route add dev eth2 table Table_eth2212.217.2.0/24

Please note: this issue isn't visible on CloudStack upgrade installation from anterior version
of until you decide to restart with clean up the network in CS.

What is the best way to fix this bug?



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