Asymmetric routing resolutions in multi-regional large scale deployments with distributed gateways
Some embodiments of the invention provide a method for providing asymmetric route resolutions in an SD-WAN. The method is performed at a first edge router at a first site in a first region connected by the SD-WAN. From a first hub router of a first cluster, the method receives a flow sent by a second edge router at a second site in a second region via a first route that points to a next-hop second hub router of a second cluster. The method identifies a default second route from the first edge router to the second edge router pointing to a next-hop third hub router of the second cluster. When the first route includes secure overlay tunnels, and source addresses of the first packet flow and the first route match, the method uses the first route to send a return flow to the second edge router to ensure symmetric routing.
1 . A method for providing asymmetric route resolutions in an SD-WAN (software-defined wide area network), the method comprising:
at a first edge router located at a first site in a first region connected by the SD-WAN, the first edge router being one of a plurality of edge routers located at a plurality of sites across a plurality of regions connected by the SD-WAN:
from a first hub router of a first hub router cluster, receiving a first packet flow originating from a second edge router located at a second site in a second region connected by the SD-WAN, the first packet flow sent by the second edge router via a first route that points to a second hub router of a second hub router cluster as a next hop;
identifying a second route that is defined as a default route for reaching the second edge router from the first edge router, the second route pointing to a third hub router of the second hub router cluster as a next hop for reaching the second edge router;
determining (i) that the first route is comprised of secure overlay tunnels between the second edge router and the first edge router and (ii) that a source network address associated with the first packet flow matches a source network address associated with the first route; and
based on said determining, using the first route to send a return second packet flow to the second edge router to ensure symmetric routing.
2 . The method of claim 1 , wherein the second edge router has a direct connection to the third hub router of the second hub router cluster.
3 . The method of claim 2 , wherein a fourth hub router of the first hub router cluster has a direct connection to the third hub router of the second hub router cluster.
4 . The method of claim 3 , wherein the second route (i) identifies the fourth hub router of the first hub router cluster as a cluster exit for reaching the second edge router and (ii) identifies the third hub router of the second hub router cluster as a cluster entrance for reaching the second edge router.
5 . The method of claim 4 , wherein:
the first hub router of the first hub router cluster has a direct connection to the second hub router of the second hub router cluster; and
the first route (i) identifies the first hub router of the first hub router cluster as a cluster exit for reaching the second edge router and (ii) identifies the second hub router of the second hub router cluster as a cluster entrance for reaching the second edge router.
6 . The method of claim 5 , wherein:
the first route is defined based on prefixes and reachability information associated with the first edge router and received by the second edge router; and
the second route is defined based on prefixes and reachability information associated with the second edge router and received by the first edge router.
7 . The method of claim 1 further comprising initiating, at the first edge router, a third flow to the second edge router using the second route, wherein the second edge router uses the second route to send a return fourth flow to the first edge router.
8 . The method of claim 1 , wherein:
the second edge router and the third hub router synchronize one or more policies to be applied to packet flows sent between the second edge router and the first edge router using the first route; and
using the first route to send the return second packet flow to the second edge router to ensure symmetric routing further ensures the one or more policies can be applied to packets in the return second packet flow.
9 . The method of claim 8 , wherein the one or more policies comprise one or more of a backhaul policy, firewall policy, intrusion detection policy, intrusion prevention policy, traffic shaping policy, monitoring policy, and resource allocation policy.
10 . The method of claim 1 , wherein determining (i) that the first route is comprised of secure overlay tunnels between the second edge router and the first edge router and (ii) that the source network address associated with the first packet flow matches the source network address associated with the first route further comprises creating an inbound overlay default route (IODR) for sending return packet flows to the second edge router.
11 . The method of claim 10 , wherein the IODR indicates the second edge router has a valid route pointing to the first edge router and the first edge router does not have a corresponding overlay route pointing to the second edge router.
12 . A non-transitory machine readable medium storing a program for execution by a set of processing units, the program for providing asymmetric route resolutions in an SD-WAN (software-defined wide area network), the program comprising sets of instructions for:
at a first edge router located at a first site in a first region connected by the SD-WAN, the first edge router being one of a plurality of edge routers located at a plurality of sites across a plurality of regions connected by the SD-WAN:
from a first hub router of a first hub router cluster, receiving a first packet flow originating from a second edge router located at a second site in a second region connected by the SD-WAN, the first packet flow sent by the second edge router via a first route that points to a second hub router of a second hub router cluster as a next hop;
identifying a second route that is defined as a default route for reaching the second edge router from the first edge router, the second route pointing to a third hub router of the second hub router cluster as a next hop for reaching the second edge router;
determining (i) that the first route is comprised of secure overlay tunnels between the second edge router and the first edge router and (ii) that a source network address associated with the first packet flow matches a source network address associated with the first route; and
based on said determining, using the first route to send a return second packet flow to the second edge router to ensure symmetric routing.
13 . The non-transitory machine readable medium of claim 12 , wherein the second edge router has a direct connection to the third hub router of the second hub router cluster.
14 . The non-transitory machine readable medium of claim 13 , wherein:
a fourth hub router of the first hub router cluster has a direct connection to the third hub router of the second hub router cluster; and
the second route (i) identifies the fourth hub router of the first hub router cluster as a cluster exit for reaching the second edge router and (ii) identifies the third hub router of the second hub router cluster as a cluster entrance for reaching the second edge router.
15 . The non-transitory machine readable medium of claim 14 , wherein:
the first hub router of the first hub router cluster has a direct connection to the second hub router of the second hub router cluster; and
the first route (i) identifies the first hub router of the first hub router cluster as a cluster exit for reaching the second edge router and (ii) identifies the second hub router of the second hub router cluster as a cluster entrance for reaching the second edge router.
16 . The non-transitory machine readable medium of claim 15 , wherein:
the first route is defined based on prefixes and reachability information associated with the first edge router and received by the second edge router; and
the second route is defined based on prefixes and reachability information associated with the second edge router and received by the first edge router.
17 . The non-transitory machine readable medium of claim 12 , the program further comprising a set of instructions for initiating, at the first edge router, a third flow to the second edge router using the second route, wherein the second edge router uses the second route to send a return fourth flow to the first edge router.
18 . The non-transitory machine readable medium of claim 12 , wherein:
the second edge router and the third hub router synchronize one or more policies to be applied to packet flows sent between the second edge router and the first edge router using the first route; and
the set of instructions for using the first route to send the return second packet flow to the second edge router to ensure symmetric routing further ensures the one or more policies can be applied to packets in the return second packet flow.
19 . The non-transitory machine readable medium of claim 18 , wherein the one or more policies comprise one or more of a backhaul policy, firewall policy, intrusion detection policy, intrusion prevention policy, traffic shaping policy, monitoring policy, and resource allocation policy.
20 . The non-transitory machine readable medium of claim 12 , wherein the set of instructions for determining (i) that the first route is comprised of secure overlay tunnels between the second edge router and the first edge router and (ii) that the source network address associated with the first packet flow matches the source network address associated with the first route further comprises a set of instructions for creating an inbound overlay default route (IODR) for sending return packet flows to the second edge router, wherein the IODR indicates the second edge router has a valid route pointing to the first edge router and the first edge router does not have a corresponding overlay route pointing to the second edge router.