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.tut...@gmail.com> 
To: "OpenStack Development Mailing List (not for usage questions)" 
<openstack-dev@lists.openstack.org> 
Cc: rantu...@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 < nyech...@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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