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Hi Randy, 

I don't have a specific use case. I just wanted to understand the scope here as the name of this blueprint ("allow multiple subnets on gateway port for router") could be a bit misleading. 

Two questions I have though: 

1. Is this talking specifically about the gateway port to the provider's next-hop router or relevant for all ports in virtual routers as well? 
2. There is a fundamental difference between v4 and v6 address assignment. With IPv4 I agree that one IP address per port is usually enough (there is the concept of secondary IP, but I am not sure it's really common). With IPv6 however you can sure have more then one (global) IPv6 on an interface. Shouldn't we support this? 


Thanks, 
Nir 

----- Original Message -----

From: "Randy Tuttle" <randy.m.tuttle at gmail.com> 
To: "OpenStack Development Mailing List (not for usage questions)" <openstack-dev at lists.openstack.org> 
Cc: rantuttl at cisco.com 
Sent: Tuesday, December 31, 2013 6:43:50 PM 
Subject: Re: [openstack-dev] [Neutron] Allow multiple subnets on gateway port for router 

Hi Nir 

Good question. There's absolutely no reason not to allow more than 2 subnets, or even 2 of the same IP versions on the gateway port. In fact, in our POC we allowed this (or, more specifically, we did not disallow it). However, for the gateway port to the provider's next-hop router, we did not have a specific use case beyond an IPv4 and an IPv6. Moreover, in Neutron today, only a single subnet is allowed per interface (either v4 or v6). So all we are doing is opening up the gateway port to support what it does today (i.e., v4 or v6) plus allow IPv4 and IPv6 subnets to co-exist on the gateway port (and same network/vlan). Our principle use case is to enable IPv6 in an existing IPv4 environment. 

Do you have a specific use case requiring 2 or more of the same IP-versioned subnets on a gateway port? 

Thanks 
Randy 


On Tue, Dec 31, 2013 at 4:59 AM, Nir Yechiel < nyechiel at redhat.com > wrote: 



Hi, 

With regards to https://blueprints.launchpad.net/neutron/+spec/allow-multiple-subnets-on-gateway-port, can you please clarify this statement: "We will disallow more that two subnets, and exclude allowing 2 IPv4 or 2 IPv6 subnets". 
The use case for dual-stack with one IPv4 and one IPv6 address associated to the same port is clear, but what is the reason to disallow more than two IPv4/IPv6 subnets to a port? 

Thanks and happy holidays! 
Nir 



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