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.

Prefixes across different branches can be aggregated to the same range when the large aggregation boundaries are configured on DC IONs. The DC core router might treat this summary route advertisement from 2 IONs in the DC as ECMP and mistakenly send some traffic to the incorrect ION, which it cannot forward. As an example traffic destined to Prefix-A at Branch-A could be sent to DC ION-B which is not the active DC ION (within HA pair) for Branch-A. in 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.