Configure BGP Community Properties

Network Requirements

• Set up EBGP neighbors between Device1 and Device2.
• Device1 introduces two direct-connect routes 100.0.0.0/24 and 200.0.0.0/24 to BGP in network mode, and set different community properties for two routes that are advertised to Device2.
• When Device2 receives routes from Device1, it applies community properties in the incoming direction of a neighbor to filter route 100.0.0.0/24 and allow route 200.0.0.0/24.

Network Topology

Figure 12–3 Networking for configuring BGP community properties

Configuration Steps

Step 1: Configure the VLAN and join the interface to the corresponding VLAN. (Omitted)

Step 2: Configure the IP addresses of the interfaces. (Omitted)

Step 3: Configure BGP.

#Configure Device1.

#Configure Device2.

#On Device1, check the BGP neighbor status.

Device1#show ip bgp summary  
BGP router identifier 200.0.0.1, local AS number 100 BGP table version is 1 
1 BGP AS-PATH entries 0 BGP community entries 
 
Neighbor    V AS       MsgRcvd MsgSent TblVer InQ OutQ Up/Down       State/PfxRcd
2.0.0.2      4 200      2            3            1        0    0       00:00:04       0 

BGP neighbors have been successfully set up between Device1 and Device2.

#Query the routing table of Device2.

Device2#show ip route bgp 
Codes: C - Connected, L - Local, S - static, R - RIP, B - BGP, i-ISIS 
       U - Per-user Static route 
       O - OSPF, OE-OSPF External, M - Management, E - IRMP, EX - IRMP external 
 
B	100.0.0.0/24 [20/0] via 2.0.0.1, 00:07:47, vlan2 
B 200.0.0.0/24 [20/0] via 2.0.0.1, 00:07:47, vlan2 

According to the queried information, Device2 has successfully learnt routes 100.0.0.0/24 and 200.0.0.0/24.

Step 4: Configure the ACL and routing policy, and set BGP community properties.

#Configure Device1.

Set different community properties for routes 100.0.0.0/24 and 200.0.0.0/24 respectively by configuring an ACL and routing policy.

Step 5: Configure a routing policy for BGP.

#Configure Device1.

#Query the BGP routing table of Device2.

Device2#show ip bgp 100.0.0.0 
BGP routing table entry for 100.0.0.0/24 
Paths: (1 available, best #1, table Default-IP-Routing-Table) 
  Not advertised to any peer 
  100 
    2.0.0.1 (metric 10) from 2.0.0.1 (10.0.0.1) 
  
     Origin IGP, metric 0, localpref 100, valid, external, best 
      Community: 100:1 
      Last update: 00:01:06 ago 
 
Device2#show ip bgp 200.0.0.0 
BGP routing table entry for 200.0.0.0/24 
Paths: (1 available, best #1, table Default-IP-Routing-Table) 
  Not advertised to any peer 
  100 
    2.0.0.1 (metric 10) from 2.0.0.1 (10.0.0.1) 
  
     Origin IGP, metric 0, localpref 100, valid, external, best 
      Community: 100:2 
      Last update: 00:01:10 ago 

According to the BGP routing table of Device2, the community property of route 100.0.0.0/24 is set to 100:1, and the community properties of route 200.0.0.0/24 is set to 100:2.

Step 6: Configure BGP route filtration.

#Configure Device2.

Step 7: Check the result.

#Query the routing table of Device2.

Device2#show ip route bgp 
Codes: C - Connected, L - Local, S - static, R - RIP, B - BGP, i-ISIS 
       U - Per-user Static route 
       O - OSPF, OE-OSPF External, M - Management, E - IRMP, EX - IRMP external 
 
B	200.0.0.0/24 [20/0] via 2.0.0.1, 00:00:53, vlan2

According to the BGP routing table of Device2, route 100.0.0.0/24 has been filtered in the incoming direction, and route 200.0.0.0/24 has been allowed.

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  After a routing policy is configured on the peer, the BGP must be reset to make the configuration take effect.
• You must configure the send-community command to advertise the community property to the peer.

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