BGP Multipath Load Sharing for Both eBGP and iBGP in an MPLS-VPN
The BGP Multipath Load Sharing for eBGP and iBGP feature allows you to configure multipath load balancing with both external BGP (eBGP) and internal BGP (iBGP) paths in Border Gateway Protocol (BGP) networks that are configured to use Multiprotocol Label Switching (MPLS) Virtual Private Networks (VPNs). This feature provides improved load balancing deployment and service offering capabilities and is useful for multi-homed autonomous systems and Provider Edge (PE) routers that import both eBGP and iBGP paths from multihomed and stub networks.
Prerequisites for BGP Multipath Load Sharing for Both eBGP and iBGP in an MPLS-VPN
Cisco Express Forwarding (CEF) or distributed CEF (dCEF) must be enabled on all participating devices.
Restrictions for BGP Multipath Load Sharing for Both eBGP and iBGP in an MPLS-VPN
Address Family Support
This feature is configured on a per VPN routing and forwarding instance (VRF) basis. This feature can be configured under both IPv4 and IPv6 VRF address families.
Memory Consumption Restriction
Each BGP multipath routing table entry will use additional memory. We recommend that you do not use this feature on a device with a low amount of available memory and especially if the device carries full Internet routing tables.
Number of Paths Limitation
The number of paths supported are limited to 2 BGP multipaths. This could either be 2 iBGP multipaths or 1 iBGP multipath and 1 eBGP multipath.
Catalyst 3850 Series Switches do not support eBGP as Provider Edge (PE) and Customer Edge (CE) routing protocol for VPN Version 4. Use Enhanced Interior Gateway Routing Protocol (EIGRP), Interior Gateway Protocol (IGP), Open Shortest Path First (OSPF) or Routing Information Protocol (RIP).
ip unnumbered command is not supported in MPLS configuration.