Route aggregation allows you to combine groups of routes with common addresses into a single entry in the routing table. This decreases the size of the routing table as well as the number of route advertisements sent by the routing device. Route aggregation works when it has one or more contributing route.

Similarly, different branch prefixes can be aggregated to the same range when the same aggregation ranges are configured on DC IONs. The DC core router might treat this summary route advertisement as ECMP and mistakenly send some traffic to ION, which it cannot forward. In this scenario, the traffic gets blackholed, meaning it is lost in the network and does not reach its intended destination. To avoid this, the admin will set the Tunnel peer address as part of the Interface configuration to send this traffic to the peer DC-ION so it can be forwarded appropriately.

Branch traffic using Standard VPN tunnels to reach the core has the potential for asymmetry. The DC-ION receives a request from the Standard VPN tunnel and forwards it to the core router. Upon receiving the response, DC-ION follows the same flow and sends it over the Standard VPN instead of fabric towards the branch, provided the route map is attached to the BGP peer over Standard VPN to prefer the Standard VPN path.