Inter-region connectivity

Gateways are defined for each geographical area, and all other sites in the area will only connect to these regional gateways. This includes both IPsec overlays and BGP sessions. As already discussed, this would be enough to provide connectivity within each region. In addition, all the regional hubs are interconnected between them, forming a full-mesh topology with BGP sessions exchanging the routes between all the regions.

Two recommended methods exist that define the routing configuration between the regions:

• eBGP
• iBGP

If cross-regional ADVPN is required, iBGP between regions will be required. If there is no requirement for ADVPN between regions, eBGP is preferred.

This section contains the following topics:

• Using EBGP between regions with intra-region ADVPN
• Using IBGP between regions with inter-region ADVPN