[ovs-discuss] [OVN]: IP address representing external destinations

Han Zhou hzhou at ovn.org
Wed Sep 16 16:00:57 UTC 2020


On Wed, Sep 16, 2020 at 5:42 AM Alexander Constantinescu <
aconstan at redhat.com> wrote:
>
> Hi
>
> I was wondering if anybody is aware of an IP address signifying "external
IP destinations"?
>
> Currently in OVN we can use the IP address 0.0.0.0/0 for match
expressions in logical routing policies / ACLs when we want to specify a
source or destination IP equating to the pseudo term: "all IP
addresses",ex: 'match="ip4.src == 10.244.2.5/32 && ip4.dst ==0.0.0.0/0"'
>
In this example it is equivalent to just "ip4.src == 10.244.2.5/32"'.

> Essentially what I would need to do for an OVN-Kubernetes feature is
specify such a match condition for south -> north traffic, i.e when the
destination IP address is external to the cluster, and most likely
"unknown" to OVN. Thus, when OVN does not know how to route it within the
OVN network topology and has no choice except sending it out the default
route.
>
> Do we have such an IP address in OVN/OVS? Would it be feasible to
introduce, in case there is none?
>
We don't have such a special IP except 0.0.0.0/0. If you have a default
route, anything "unknown" would just hit the default route, right? Why
would you need another IP for this purpose? In logical_router_static_route
the priority is based on prefix length. In policies/ACL you will need to
make sure the priorities are set properly to achieve the default-route
behavior.

Thanks,
Han

> Thanks in advance!
>
> --
>
> Best regards,
>
>
> Alexander Constantinescu
>
> Software Engineer, Openshift SDN
>
> Red Hat
>
> aconstan at redhat.com
>
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