Example for Configuring the BGP Community Attribute

Procedure

1. Configure the VLANs to which interfaces belong and assign IP addresses to VLANIF interfaces.

   # Configure SwitchC.

   <HUAWEI> system-view

   [~HUAWEI] sysname SwitchC

   [*HUAWEI] commit

   [~SwitchC] vlan 30

   [*SwitchC-vlan30] quit

   [*SwitchC] interface 10ge 1/0/3

   [*SwitchC-10GE1/0/3] port link-type trunk

   [*SwitchC-10GE1/0/3] port trunk allow-pass vlan 30

   [*SwitchC-10GE1/0/3] quit

   [*SwitchC] interface vlanif 30

   [*SwitchC-Vlanif30] ip address 192.168.3.2 255.255.255.0

   [*SwitchC-Vlanif30] quit

   [*SwitchC] commit

   The configurations of SwitchA and SwitchB are similar to the configuration of SwitchC, and are not mentioned here.

2. Configure EBGP connections.

   # Configure SwitchA.

   [~SwitchA] bgp 10

   [*SwitchA-bgp] router-id 172.16.1.1

   [*SwitchA-bgp] peer 192.168.2.2 as-number 20

   [*SwitchA-bgp] ipv4-family unicast

   [*SwitchA-bgp-af-ipv4] network 10.1.1.0 255.255.255.0

   [*SwitchA-bgp-af-ipv4] commit

   [~SwitchA-bgp-af-ipv4] quit

   # Configure SwitchB.

   [~SwitchB] bgp 20

   [*SwitchB-bgp] router-id 172.16.2.2

   [*SwitchB-bgp] peer 192.168.2.1 as-number 10

   [*SwitchB-bgp] peer 192.168.3.2 as-number 30

   [*SwitchB-bgp] commit

   [~SwitchB-bgp] quit

   # Configure SwitchC.

   [~SwitchC] bgp 30

   [*SwitchC-bgp] router-id 172.16.3.3 

   [*SwitchC-bgp] peer 192.168.3.1 as-number 20

   [*SwitchC-bgp] commit

   [~SwitchC-bgp] quit

   # View the BGP routing table of SwitchB.

   [~SwitchB] display bgp routing-table 10.1.1.0

   BGP local router ID : 172.16.2.2
    Local AS number : 20
    Paths:   1 available, 1 best, 1 select, 0 best-external, 0 add-path
    BGP routing table entry information of 10.1.1.0/24:
    From: 192.168.2.1 (172.16.1.1)
    Route Duration: 0d00h00m37s
    Direct Out-interface: Vlanif20
    Original nexthop: 192.168.2.1
    Qos information : 0x0
    AS-path 10, origin igp, MED 0, pref-val 0, valid, external, best, select, pre 255
    Advertised to such 2 peers:
       192.168.2.1
       192.168.3.2
   

   The preceding command output shows that SwitchB has advertised the received route to SwitchC in AS 30.

   # View the BGP routing table of SwitchC.

   [~SwitchC] display bgp routing-table

    BGP Local router ID is 172.16.3.3

    Status codes: * - valid, > - best, d - damped, h - history,

                  i - internal, s - suppressed, S - Stale

    Origin      : i - IGP, e - EGP, ? - incomplete

    Total Number of Routes: 1

         Network            NextHop        MED        LocPrf    PrefVal Path/Ogn

    *>   10.1.1.0/24        192.168.3.1                           0      20 10i

   The preceding command output shows that SwitchC has learned the route to 10.1.1.0/24 from SwitchB.

3. Configure the BGP Community attribute.

   # Configure a route-policy on SwitchA to prevent SwitchB from advertising the routes advertised by SwitchA to AS 30.

   [~SwitchA] route-policy comm_policy permit node 10

   [*SwitchA-route-policy] apply community no-export

   [*SwitchA-route-policy] commit

   [~SwitchA-route-policy] quit

   # Apply the route-policy.

   [~SwitchA] bgp 10

   [~SwitchA-bgp] ipv4-family unicast

   [~SwitchA-bgp-af-ipv4] peer 192.168.2.2 route-policy comm_policy export

   [*SwitchA-bgp-af-ipv4] peer 192.168.2.2 advertise-community

   [*SwitchA-bgp-af-ipv4] commit

   # View the BGP routing table of SwitchB.

   [~SwitchB] display bgp routing-table 10.1.1.0

   BGP local router ID : 172.16.2.2
    Local AS number : 20
    Paths:   1 available, 1 best, 1 select, 0 best-external, 0 add-path
    BGP routing table entry information of 10.1.1.0/24:
    From: 192.168.2.1 (172.16.1.1)
    Route Duration: 0d00h00m12s
    Direct Out-interface: Vlanif20
    Original nexthop: 192.168.2.1
    Qos information : 0x0
    Community:no-export
    AS-path 10, origin igp, MED 0, pref-val 0, valid, external, best, select, pre 255
    Not advertised to any peers yet

   In the BGP routing table of SwitchB, you can view the configured Community attribute. There is no route to 10.1.1.0/24 in the BGP routing table of SwitchC.