[OmniOS-discuss] Routing challlenges

Schweiss, Chip chip at innovates.com
Thu Apr 7 18:50:13 UTC 2016


On Thu, Apr 7, 2016 at 12:51 PM, Michael Talbott <mtalbott at lji.org> wrote:

> Oh, I see. Sorry about that, reading it on my phone didn't render your
> diagram properly ;)
>
> The reason this is happening is because the omnios box has knowledge of
> both subnets in its routing table and it always takes the shortest path to
> reach an ip destination.
>

That's definitely the reason, but not correct when stateful firewalls are
involved.

>
> So you will need to put the "clients" in a unique subnet that always
> passes through the firewall in both directions (in a subnet that's not
> shared by the omnios machines). Any attempt to add/modify a static route to
> the omnios box to resolve this will likely fail (it'll just move the
> problem from one network to the other one and cause your "services" network
> to route improperly).
>

The problem is each person who manages these (there are 4) are also clients
of the services (SMB, NFS).

For management, going through the firewall is fine, it is low volume, but
the services need to be on the same VLAN or else the 1gb firewall will
choke on the 10gb services.


> Either that, or remove the firewall as a hop, set sshd to listen only on
> the management IP, and add a management vlan interface to the clients
> allowed to connect.
>
>
I've considered this too, but I have some floating IP attached to zfs pools
in an HA cluster that SSH needs to bind to.

Unless I can get the network stack on the management vlan to act
independently of the other interfaces, it may come to modifying the
sshd_config and restarting ssh each time a pool is started or stopped on a
host.

-Chip



> Michael
>
>
> On Apr 7, 2016, at 10:25 AM, Michael Talbott <mtalbott at lji.org> wrote:
>
> It sounds like you're using the same subnet for management and service
> traffic, that would be the problem causing the split route. Give each vlan
> a unique subnet and traffic should flow correctly.
>
> Michael
> Sent from my iPhone
>
> On Apr 7, 2016, at 8:52 AM, Schweiss, Chip <chip at innovates.com> wrote:
>
> On several of my OmniOS hosts I have a setup a management interface for
> SSH access on an independent VLAN.   There are service vlans attached to
> other nics.
>
> The problem I am having is that when on privileged machine on one of the
> vlans also on the service side that has access to the management SSH port
> the TCP SYN comes in the management VLAN but the SYNACK goes out the
> service VLAN instead of routing back out its connecting port.   This causes
> a split route and the firewall blocks the connection because the connection
> never appears complete.
>
> Traffic is flowing like this:
> client                   firewall                 omnnios
> 10.28.0.106 ->   10.28.0.254->10.28.125.254  -> 10.28.125.44
>
> 10.28.0.106  <--------------------------------- 10.28.0.44
>
> How can I cause connections to only communicate on the vlan that the
> connection is initiated from?
>
> I don't want to use the 10.28.0.44 interface because that is a virtual IP
> and will not always be on the same host.
>
> -Chip
>
>
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