Current state:
The current OVN IC (interconnect) support is limited to adding transit switches that interconnect different OVN deployments (across AZ - availability zones):
In practice deployments may look like this:
AZ1 AZ2 --- --- GR1 GR2 --- N2 | | +-- TS --+ | (intra-AZ routers may also be attached here) VIF1 --+--- VIF2
Where "TS" stands for "transit switch" interconnecting AZ1 and AZ2; "GR" stands for "zone-specific (gateway) router".
This kind of topology has a few significant limitations:
- packets routed between GR2 and GR1 always go through the transit switch TS
- if VIF1 (AZ1) needs to communicate with a network (N2) that's behind GR2 (AZ2) then it needs to either:
- have a route for N2 via GR2's IP
- OR assuming it has a default route via the local GR1 use that one in which case traffic flows as: VIF1 -> TS -> GR1 -> TS -> GR2 -> N2.
Proposal:
Introduce a new type of logical router, logical transit distributed router.
The logical topology above could be changed to something like:
AZ1 AZ2 --- --- GR1 GR2 --- N2 | | +-- TDR --+ | TS (intra-AZ routers may also be attached here) | VIF1 --+--- VIF2
Where "TDR" stands for "transit distributed router".
This simplifies the routing, allowing VIF1/VIF2 to have a single (identical) default gateway while ensuring that traffic from VIF1 from N2 flows as: VIF1 -> TS -> TDR -> GR2 -> N2.
With this proposal, Transit Logical Routers will likely be able to support only a subset of the features a regular Logical Router supports. For example, a Transit Logical Router cannot be a Gateway Router (as we don't currently have a way to distribute conntrack state).
- is related to
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OCPBUGS-43354 UDN: L2: OVN's lb_force_snat_ip=routerip doesn't work when multiple networks are set on LRP
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- New
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- To Do
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SDN-5015 [L2] [Services] [SGW] Add support for External->Services traffic in user-defined primary networks
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- In Progress
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