BGP load balancing configuration example

As shown in Figure 62, run EBGP between Switch A and Switch B and between Switch A and Switch C. Run IBGP between Switch B and Switch C. Configure load balancing over the two EBGP links on Switch A.

On Switch A, establish EBGP connections with Switch B and Switch C. Configure BGP to advertise network 8.1.1.0/24 to Switch B and Switch C, so that Switch B and Switch C can access the internal network connected to Switch A.

On Switch B, establish an EBGP connection with Switch A and an IBGP connection with Switch C. Configure BGP to advertise network 9.1.1.0/24 to Switch A, so that Switch A can access the intranet through Switch B. Configure a static route to interface loopback 0 on Switch C (or use a routing protocol like OSPF) to establish the IBGP connection.

On Switch C, establish an EBGP connection with Switch A and an IBGP connection with Switch B. Configure BGP to advertise network 9.1.1.0/24 to Switch A, so that Switch A can access the intranet through Switch C. Configure a static route to interface loopback 0 on Switch B (or use another protocol like OSPF) to establish the IBGP connection.

Configure load balancing on Switch A.

1. Configure IP addresses for interfaces. (Details not shown.)

2. Configure BGP connections:

   # Configure Switch A.

   <SwitchA> system-view
   [SwitchA] bgp 65008
   [SwitchA-bgp] router-id 1.1.1.1
   [SwitchA-bgp] peer 3.1.1.1 as-number 65009
   [SwitchA-bgp] peer 3.1.2.1 as-number 65009
   [SwitchA-bgp] address-family ipv4 unicast
   [SwitchA-bgp-ipv4] peer 3.1.1.1 enable
   [SwitchA-bgp-ipv4] peer 3.1.2.1 enable
   [SwitchA-bgp-ipv4] network 8.1.1.1 24
   [SwitchA-bgp-ipv4] quit
   [SwitchA-bgp] quit
   

   # Configure Switch B.

   <SwitchB> system-view
   [SwitchB] bgp 65009
   [SwitchB-bgp] router-id 2.2.2.2
   [SwitchB-bgp] peer 3.1.1.2 as-number 65008
   [SwitchB-bgp] peer 3.3.3.3 as-number 65009
   [SwitchB-bgp] peer 3.3.3.3 connect-interface loopback 0
   [SwitchB-bgp] address-family ipv4 unicast
   [SwitchB-bgp-ipv4] peer 3.1.1.2 enable
   [SwitchB-bgp-ipv4] peer 3.3.3.3 enable
   [SwitchB-bgp-ipv4] network 9.1.1.0 24
   [SwitchB-bgp-ipv4] quit
   [SwitchB-bgp] quit
   [SwitchB] ip route-static 3.3.3.3 32 9.1.1.2
   

   # Configure Switch C.

   <SwitchC> system-view
   [SwitchC] bgp 65009
   [SwitchC-bgp] router-id 3.3.3.3
   [SwitchC-bgp] peer 3.1.2.2 as-number 65008
   [SwitchC-bgp] peer 2.2.2.2 as-number 65009
   [SwitchC-bgp] peer 2.2.2.2 connect-interface loopback 0
   [SwitchC-bgp] address-family ipv4 unicast
   [SwitchC-bgp-ipv4] peer 3.1.2.2 enable
   [SwitchC-bgp-ipv4] peer 2.2.2.2 enable
   [SwitchC-bgp-ipv4] network 9.1.1.0 24
   [SwitchC-bgp-ipv4] quit
   [SwitchC-bgp] quit
   [SwitchC] ip route-static 2.2.2.2 32 9.1.1.1
   

   # Display the BGP routing table on Switch A.

   [SwitchA] display bgp routing-table ipv4
   
    Total number of routes: 3
   
    BGP local router ID is 1.1.1.1
    Status codes: * - valid, > - best, d - damped, h - history,
                  s - suppressed, S - Stale, i - internal, e - external
                  Origin: i - IGP, e - EGP, ? - incomplete
   
        Network            NextHop         MED        LocPrf     PrefVal Path/Ogn
   
   * >  8.1.1.0/24         8.1.1.1         0                     0       i
   * >e 9.1.1.0/24         3.1.1.1         0                     0       65009i
   *  e                    3.1.2.1         0                     0       65009i
   

   • The output shows two valid routes to destination 9.1.1.0/24. The route with next hop 3.1.1.1 is marked with a greater-than sign (>), indicating it is the best route (because the ID of Switch B is smaller). The route with next hop 3.1.2.1 is marked with an asterisk (*), indicating it is a valid route, but not the best.

   • By using the display ip routing-table command, you can find only one route to 9.1.1.0/24 with next hop 3.1.1.1 and outbound interface VLAN-interface 200.

3. Configure loading balancing:

   Because Switch A has two routes to reach AS 65009, configuring load balancing over the two BGP routes on Switch A can improve link usage.

   # Configure Switch A.

   [SwitchA] bgp 65008
   [SwitchA-bgp] address-family ipv4 unicast
   [SwitchA-bgp-ipv4] balance 2
   [SwitchA-bgp-ipv4] quit
   [SwitchA-bgp] quit
   

# Display the BGP routing table on Switch A.

[SwitchA] display bgp routing-table ipv4

 Total number of routes: 3

 BGP local router ID is 1.1.1.1
 Status codes: * - valid, > - best, d - damped, h - history,
               s - suppressed, S - Stale, i - internal, e - external
               Origin: i - IGP, e - EGP, ? - incomplete

     Network            NextHop         MED        LocPrf     PrefVal Path/Ogn

* >  8.1.1.0/24         8.1.1.1         0                     0       i
* >e 9.1.1.0/24         3.1.1.1         0                     0       65009i
* >e                    3.1.2.1         0                     0       65009i

• The route 9.1.1.0/24 has two next hops, 3.1.1.1 and 3.1.2.1, both of which are marked with a greater-than sign (>), indicating they are the best routes.

• By using the display ip routing-table command, you can find two routes to 9.1.1.0/24. One has next hop 3.1.1.1 and outbound interface VLAN-interface 200, and the other has next hop 3.1.2.1 and outbound interface VLAN-interface 300.