Thanks for this clarification. Just wondering: Do multiple network nodes (router + dhcp) help to exceed the 4k subnet limitation? In such a scenario, will dhcp + routing be distributed or is a second network node just something like a hot-standby?
Thanks! -- Andreas (irc: scheuran) On Thu, 2014-09-18 at 09:47 -0400, George Mihaiescu wrote: > The VLAN ID is only locally significant to each compute node, so same > subnet belonging to same tenant could would have different VLAN tags > on different compute nodes. > > VLAN tag 1 could be used by subnet1 of tenant A on node1 and by > subnet1 of tenant B on node 2, with no conflicts. > > > > Both VXLAN and GRE add a 24-bit header, so the maximum number of > tunnels is 16 million but each compute node can locally implement only > a maximum of 4096 different neutron subnets. > > What are the chances that you have more than 4096 instances on a > compute node, each connected to a different neutron subnet? > > What are the chances that you have more than 409 instances on a > compute node, each connected to 10 different neutron subnets? > > > > The same limitation applies to the Neutron node (because a tunnel > endpoint exists there as well), so you cannot have a Neutron node > where a L3 agent and a DHCP agent serve more than 4096 Neutron > subnets, but you would hit other limits by then. > > > > George > > > > > ______________________________________________________________________ > From: BYEONG-GI KIM [mailto:kimbyeon...@gmail.com] > Sent: Wednesday, September 17, 2014 10:41 PM > To: George Mihaiescu; openstack@lists.openstack.org > Subject: Re: [Openstack] Question about VXLAN support > > > > > Dear George > > > > > Thank you for the reply. > > > > > > I'm a little confused about your reply. > > > > > > Can be the same tag number assigned to different tenant? For example, > I assume the situation where a subnet 1 assigned tag number 1 and it > belongs to tenant A, and a subnet b is also assigned tag number 1 and > it belongs to tenant B. Or, should be the tag number different even if > subnets belong to different tenant? > > > > > > If the later case, the tag number seems much more strictly limited, > because a tenant can have many subnet. If a subnet has 10 subnets, > which means 10 tag numbers must be assigned, the openstack only create > about 400 tenants. > > > > > > Is the VXLAN network type in OpenStack really scalable comparing with > VLAN or GRE? Or does the current OpenStack just provide functionality > to handle VXLAN header? > > > > > > Please let me know good example about VXLAN usage, which can provide > scalability for multi-tenant on OpenStack. I'd like to know whether > more than 100000 tenants could be handled by VXLAN on the latest > OpenStack implementation or not. > > > > > > Best regards > > > > > > Byeong-Gi KIM > > > > > 2014-09-18 11:20 GMT+09:00 George Mihaiescu <george.mihaie...@q9.com>: > > The internal VLAD ID is indeed limited to 4096 but this internal tag > number is used to isolate different neutron subnets, not tenants. > > A tenant could create 10 neutron networks each with its own subnet and > then start 10 instances each attached to a separate net/subnet. If > these instances would be scheduled on the same compute node then they > would all use different internal VLAN IDs (locally unique to that > node). > > > > Basically, you’re right that there is a built-in limitation of 4096 > instances attached to 4096 different Neutron net/subnets on a compute > node, but it’s not realistic to actually start that many instances on > a compute node. > > > > George > > > > > > > ______________________________________________________________________ > From: BYEONG-GI KIM [mailto:kimbyeon...@gmail.com] > Sent: Wednesday, September 17, 2014 8:47 PM > To: openstack@lists.openstack.org > Subject: [Openstack] Question about VXLAN support > > > > > Hello. > > > > > I have a question about the VXLAN support on OpenStack. > > > > > > As far as I know, the OVS operates like the below: > > > > > > 1. A tag number is created to identify each tenant, and it is used > between br-int and br-tun. Furthermore the tag number is identified as > a VLAN ID (I checked it via tcpdump). > > > > > > 2. After the packet arrived at br-tun, it is encapsulated and VNI > (VXLAN Network Identifier) is attached. The binding information > between the VLAN ID (tag number) and the VNI is stored in OVSDB. > > > > > > If the operation is correct, it seems that the number of tenants which > can be created is still limited to about 4000, which is the supported > range of VLAN, because the tag number is used to identify each tenant > at the inside of br-int regardless of the supported range of VNI. > > > > > > If more than 5000 tenants are created in a Compute Node, how could be > these identified after the packet arrived at br-int? In the theory, > the 4500th tenant should have 4500 tag number but the tag number is > presented as VLAN ID so that it cannot be assigned over 4096. > > > > > > Any advice and comment would really be appreciated. > > > > > > Best regards > > > > > > Byeong-Gi KIM > > > > > > _______________________________________________ > Mailing list: http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack > Post to : openstack@lists.openstack.org > Unsubscribe : http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack _______________________________________________ Mailing list: http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack Post to : openstack@lists.openstack.org Unsubscribe : http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack