[adding Aaron Rosen] On Wed, Jul 29, 2015 at 12:20:30PM +0300, Gal Sagie wrote: > Currently Neutron support defining few subnets (IP cidrs) on a network > (logical switch) > and connecting them to the same router (or different routers). > Currently in the NB schema, the logical switch can be connected only to one > logical > router port. > > This needs to be extended so a logical switch can have more then one > logical router > port reference to support the above use case.
Limiting a logical switch to a single router port is an intentional design decision. It means that a packet traverses at most two logical switches (one at ingress, one at egress), which simplifies some of the logical switch design, and it prevents loops. VMware's NVP controller uses the same design, for those reasons and others. The NVP paper from NSDI 2014 (see http://benpfaff.org/papers/net-virt.pdf) puts it this way: As an optimization, we constrain the logical topology such that logical L2 destinations can only be present at its edge[6]. This restriction means that the OVS flow table of a sending hypervisor needs only to have flows for logical datapaths to which its local VMs are attached as well as those of the L3 routers of the logical topology; the receiving hypervisor is determined by the logical IP destination address, leaving the last logical L2 hop to be executed at the receiving hypervisor. [6] We have found little value in supporting logical routers interconnected through logical switches without tenant VMs. Are you sure that Neutron supports multiple router ports per switch? Russell Bryant (in IRC) and Aaron Rosen (in a quick in-person chat) seemed doubtful. _______________________________________________ dev mailing list dev@openvswitch.org http://openvswitch.org/mailman/listinfo/dev
