Cisco Cisco IOS Software Release 12.2(14)S

BGP load balancing or multipath load balancing must be configured before this feature is enabled. 

BGP extended community exchange must be enabled between iBGP neighbors to which the link 
bandwidth attribute is to be advertised. 

Cisco Express Forwarding (CEF) or distributed CEF (dCEF) must be enabled on all participating 
routers.

This feature can be configured only under IPv4 and VPNv4 address family sessions. 

BGP can originate the link bandwidth community only for directly connected links to eBGP 
neighbors. 

Both iBGP and eBGP load balancing are supported in IPv4 and VPNv4 address families. However, 
eiBGP load balancing is supported only in VPNv4 address-family. 

To configure the BGP Link Bandwidth feature, you must understand the following concept: 

The BGP Link Bandwidth feature used to enable multipath load balancing for external links with 
unequal bandwidth capacity. This feature is enabled under an IPv4 or VPNv4 address family sessions by 
entering the bgp dmzlink-bw command. This feature supports both iBGP, eBGP multipath load 
balancing, and eiBGP multipath load balancing in Multiprotocol Label Switching (MPLS) Virtual 
Private Networks (VPNs). When this feature is enabled, routes learned from directly connected external 
neighbor are propagated through the internal BGP (iBGP) network with the bandwidth of the source 
external link.

The link bandwidth extended community indicates the preference of an autonomous system exit link in 
terms of bandwidth. This extended community is applied to external links between directly connected 
eBGP peers by entering the neighbor dmzlink-bw command. The link bandwidth extended community 
attribute is propagated to iBGP peers when extended community exchange is enabled with the neighbor 
send-community command.