Two subnets under same network context.

Slawek Kaplonski skaplons at
Sun Aug 2 11:27:58 UTC 2020


This is "normal". You can have many subnets (both IPv4 and IPv6 in the 
one network). By default Neutron will associate to the port IP address 
only from one subnet of one type (IPv4/IPv6) but You can change it and 
tell Neutron to allocate for the port IP adresses from more than one subnet.
If You have both IPv4 and IPv6 subnets in the network, Neutron will by 
default allocate one IPv4 and one IPv6 to each port. But again, You can 
manually tell Neutron to use e.g. only IPv6 address for specific port.

Please check [1] and [2] for more details.


W dniu 01.08.2020 o 23:36, Anil Jangam pisze:
> Hi,
> I have observed that one can create two subnets under the same network
> scope. See below an example of the use case.
> [image: Screen Shot 2020-08-01 at 2.22.15 PM.png]
> Upon checking the data structures, I saw that the segment type (vlan) and
> segment id (55) is associated with the "network" object and not with the
> "subnet" (I was under impression that the segment type (vlan) and segment
> id (55) would be allocated to the "subnet").
> When I create the VM instances, they always pick the IP address from the
> SUBNET1-2 IP range. If the segment (vlan 55) is associated with "network"
> then what is the reason two "subnets" are allowed under it?
> Does it mean that VM instances from both these subnets would be configured
> under the same VLAN?
> /anil.

Slawek Kaplonski
Principal software engineer
Red Hat

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