BGP community configuration example

As shown in Figure 67, Switch B establishes EBGP connections with Switch A and Switch C. Configure NO_EXPORT community attribute on Switch A to make routes from AS 10 not advertised by AS 20 to any other AS.

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

2. Configure EBGP:

   # Configure Switch A.

   <SwitchA> system-view
   [SwitchA] bgp 10
   [SwitchA-bgp] router-id 1.1.1.1
   [SwitchA-bgp] peer 200.1.2.2 as-number 20
   [SwitchA-bgp] address-family ipv4 unicast
   [SwitchA-bgp-ipv4] peer 200.1.2.2 enable
   [SwitchA-bgp-ipv4] network 9.1.1.0 255.255.255.0
   [SwitchA-bgp] quit
   

   # Configure Switch B.

   <SwitchB> system-view
   [SwitchB] bgp 20
   [SwitchB-bgp] router-id 2.2.2.2
   [SwitchB-bgp] peer 200.1.2.1 as-number 10
   [SwitchB-bgp] peer 200.1.3.2 as-number 30
   [SwitchB-bgp] address-family ipv4 unicast
   [SwitchB-bgp-ipv4] peer 200.1.2.1 enable
   [SwitchB-bgp-ipv4] peer 200.1.3.2 enable
   [SwitchB-bgp-ipv4] quit
   [SwitchB-bgp] quit
   

   # Configure Switch C.

   <SwitchC> system-view
   [SwitchC] bgp 30
   [SwitchC-bgp] router-id 3.3.3.3 
   [SwitchC-bgp] peer 200.1.3.1 as-number 20
   [SwitchC-bgp] address-family ipv4 unicast
   [SwitchC-bgp-ipv4] peer 200.1.3.1 enable
   [SwitchC-bgp-ipv4] quit
   [SwitchC-bgp] quit
   

   # Display the BGP routing table on Switch B.

   [SwitchB] display bgp routing-table ipv4 9.1.1.0
   
    BGP local router ID: 2.2.2.2
    Local AS number: 20
   
    Paths:   1 available, 1 best
   
    BGP routing table information of 9.1.1.0/24:
    From            : 200.1.2.1 (1.1.1.1)
    Relay nexthop   : 200.1.2.1
    Original nexthop: 200.1.2.1
    OutLabel        : NULL
    AS-path         : 10
    Origin          : igp
    Attribute value : pref-val 0
    State           : valid, external, best,
   

   # Display advertisement information of network 9.1.1.0 on Switch B.

   [SwitchB] display bgp routing-table ipv4 9.1.1.0 advertise-info
   
    BGP local router ID: 2.2.2.2
    Local AS number: 20
   
    Paths:   1 best
   
    BGP routing table information of 9.1.1.0/24:
    Advertised to peers (1 in total):
       200.1.3.2
   

   The output shows that Switch B can advertise the route with the destination 9.1.1.0/24 to other ASs through BGP.

   # Display the BGP routing table on Switch C.

   [SwitchC] display bgp routing-table ipv4
   
    Total number of routes: 1
   
    BGP local router ID is 3.3.3.3
    Status codes: * - valid, > - best, d - dampened, h - history,
                  s - suppressed, S - stale, i - internal, e - external
                  Origin: i - IGP, e - EGP, ? - incomplete
   
        Network            NextHop         MED        LocPrf     PrefVal Path/Ogn
   
   * >e 9.1.1.0/24         200.1.3.1                             0       20 10i
   

   The output shows that Switch C has learned route 9.1.1.0/24 from Switch B.

3. Configure BGP community:

   # Configure a routing policy.

   [SwitchA] route-policy comm_policy permit node 0
   [SwitchA-route-policy-comm_policy-0] apply community no-export
   [SwitchA-route-policy-comm_policy-0] quit
   

   # Apply the routing policy.

   [SwitchA] bgp 10
   [SwitchA-bgp] address-family ipv4 unicast
   [SwitchA-bgp-ipv4] peer 200.1.2.2 route-policy comm_policy export
   [SwitchA-bgp-ipv4] peer 200.1.2.2 advertise-community
   

# Display the routing table on Switch B.

[SwitchB] display bgp routing-table ipv4 9.1.1.0

 BGP local router ID: 2.2.2.2
 Local AS number: 20

 Paths:   1 available, 1 best

 BGP routing table information of 9.1.1.0/24:
 From            : 200.1.2.1 (1.1.1.1)
 Relay nexthop   : 200.1.2.1
 Original nexthop: 200.1.2.1
 OutLabel        : NULL
 Community       : No-Export
 AS-path         : 10
 Origin          : igp
 Attribute value : pref-val 0
 State           : valid, external, best,

# Display advertisement information for the route 9.1.1.0 on Switch B.

[SwitchB] display bgp routing-table ipv4 9.1.1.0 advertise-info

 BGP local router ID: 2.2.2.2
 Local AS number: 20

 Paths:   1 best

 BGP routing table information of 9.1.1.0/24:
 Not advertised to any peers yet

# Display the BGP routing table on Switch C.

[SwitchC] display bgp routing-table ipv4

 Total number of routes: 0

The output shows BGP has not learned any route.