Configuring Unicast Route Load Balancing

Before configuring unicast route load balancing, please attention to the maximum number of routes of the unicast routing table. The route load balancing increases the number of routes.

Configuring Load Balancing Among IGP Routes

Configuration Procedure:

Deploy multiple links of the same cost/metric to achieve load balancing.

Modification of IGP cost impacts on BGP route selection.
(Optional) Set the maximum number of routes among which load balancing is performed. For different products and different protocols, the maximum number of equal-cost routes is different, as shown in Table 1.

**Table 1** Configuration Guide for Maximum Number of IGP Load-balancing
Route Type	Command Format	Views	Maximum number
Static route	NA	-	64
OSPF	maximum load-balancing number	OSPF view	64
OSPFv3	maximum load-balancing number	OSPFv3 view	64
IS-IS	maximum load-balancing number	IS-IS view IS-IS topology view IS-IS IPv6 topology view	64
IS-IS IPv6	ipv6 maximum load-balancing number NOTE: This command is valid only for an IPv6 base topology, and invalid for IPv6 routes in multi-topology. The maximum load-balancing number command in the IS-IS IPv6 topology view is used to configure load balancing among IPv6 routes in multi-topology.	IS-IS view	64
RIP	maximum load-balancing number	RIP view	64
RIPng	maximum load-balancing number	RIPng view	64

For different products and different protocols, the maximum number of equal-cost routes is different. The maximum value can be adjusted by purchasing license files.

Configuring Load Balancing Among BGP Routes

There are three solutions for Load Balancing Among BGP Routes

Solution 1: Static routes or equal-cost IGP routes for BGP route recursion. Configuration Procedure:

Establish the BGP peers relationship using Loopback interface.

If loopback interfaces are used to establish an EBGP peer relationship, the peer ebgp-max-hop command (hop-count >= 2) must be run; otherwise, the peer relationship cannot be established.
Deploy multiple links between the BGP peers.
Configure multiple static routes or equal-cost IGP routes to the loopback interface address of the remote BGP peer.
Set the maximum number of routes among which load balancing is performed, see Table 2.

By default, the maximum number of equal-cost BGP routes is 1, that is, the load balancing among BGP routes is not enabled by default.

If the maximum load-balancing command is configured, when the routes advertised from the EBGP peer are advertised to IBGP peers, the next hop address of the routes are set as the local IP address by which the IBGP peer is established. If the maximum load-balancing command is not configured, the next hop address of the routes is not changed when the routes are advertised to the IBGP peer, unless the peer next-hop-local command is configured.

**Table 2** Configuration Guide for Maximum Number of BGP Load-balancing
Route Type	Command Format	Views	Default value
BGP	Run the maximum load-balancing [ ebgp \| ibgp ] number command to set the maximum number of equal-cost routes. (Optional) Run the load-balancing as-path-ignore command to configure a router to ignore comparing the AS_Path attributes of the routes among which load balancing is performed. Run the commit.	BGP view BGP IPv4 unicast address family view BGP IPv6 unicast address family view BGP-VPN instance IPv4 address family view BGP-VPN instance IPv6 address family view	1
EBGP and IBGP	Run the maximum load-balancing eibgp eibgp number command to set the maximum number of equal-cost routes. (Optional) Run the load-balancing as-path-ignore command to configure a router to ignore comparing the AS_Path attributes of the routes among which load balancing is performed. Run the commit.	BGP-VPN instance IPv4 address family view BGP-VPN instance IPv6 address family view	1

For application case of Solution 1, see BGP Route Load Balancing in an RR Scenario.

Solution 2: Modify BGP route attributes according to the rule of BGP route selection. Configuration Procedure:
1. Deploy multiple links between the BGP peers.
2. Modify BGP route attributes according to the rule of BGP route selection. For detailed information about the rule of BGP route selection, see Load Balancing Among BGP Routes.
3. Set the maximum number of routes among which load balancing is performed, see the above table.
Solution 3: Divide the destination addresses into multiple groups and deploy multiple links between the BGP peers, one link for each group. Suitable scenarios: there are multiple EBGP peers in the same AS to the same destination. Configuration Procedure:
1. Configure a static route to the Loopback address of the EBGP peer on each EBGP routers. The static routes are used for BGP route recursion, and then traffic is load-balanced among the BGP routes.
2. Configure ACL, IP-prefix, AS-Path filter, community-filter, extcommunity-filter, or Route Distinguisher (RD) filter to divide the destination addresses into multiple groups.
3. Configure route policies to set the next hop address as the Loopback address of the EBGP peer so that one link is used for each group.
4. Apply the route policies to the routes advertisement from the EBGP routers to RR or IBGP peer.
For application case of Solution 3, see Solution to the Low Equal-Cost Route Specification on the Remote Device Without Interrupting Services.

Follow-up Procedure

Run the save command to save the current configuration to the configuration file when a set of configuration is finished and the expected functions have been achieved.