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[Ahmed Al-Mehdi <ahmedalmehdi@xxxxxxxxx>]

Hello,

I have a few questions related to private and external network in Quantum.
 I am running into some odd behavior with networking related to my VM
instance that I am trying to resolve.


I used the following commands to create a private network and a router to
which it is attached:

# quantum net-create --tenant-id $put_id_of_project_one net_proj_one
--provider:network_type vlan --provider:physical_network physnet1
--provider:segmentation_id 1024
# quantum subnet-create --tenant-id $put_id_of_project_one net_proj_one
10.10.10.0/24 (step a)

# quantum router-create --tenant-id $put_id_of_project_one router_proj_one
# quantum router-interface-add $put_router_proj_one_id_here
$put_subnet_id_here

Q: Upon executing "step a", does Quantum reserve the first IP address from
the subnet's cidr range as a gateway_ip addr?  If so, why?  Does that
happen even if the subnet is not attached to a router?


I then used the following steps to create an external network:

# quantum net-create --tenant-id $put_id_of_service_tenant ext_net
--router:external=True
# quantum subnet-create --tenant-id $put_id_of_service_tenant
--allocation-pool start=192.168.50.102,end=192.168.50.126 --gateway
192.168.50.1 ext_net192.168.50.100/24 --enable_dhcp=False  (step b)

Q: I am trying to understand the different options passed to " quantum
subnet-create" for an external network:

-  start=192.168.50.102,end=192.168.50.126 : Is this the list of
floating-IPs that are accessible from outside world?  And these would be
mapped to a private  IP addr?

-  192.168.50.1:  Is this the outside gateway IP addr (provided by our IT)?

-  192.168.50.100/24:  Is 192.168.50.100 assigned (reserved) for any
purpose?  What is this cidr represent?

-  enable_dhcp=False : What is the effect of setting this to true?  I mean
how does Quantum dole out a floating IP mapping to which private IP,
randomly?


Thank you,
Ahmed.