Example for Configuring Basic BGP Functions

Before building BGP networks, you need to configure basic BGP functions.

Networking Requirements

If multiple ASs want to access each other, these ASs must exchange their local routes. If multiple routers exist in the ASs, a great deal of routing information will be exchanged between ASs, which consumes lots of bandwidth resources. To address this issue, you can configure basic BGP functions.

In Figure 1, DeviceA is in AS 65008. DeviceB, DeviceC, and DeviceD are in AS 65009. The routing tables of these routers store many routes, and the routes change frequently. After BGP is enabled on the routers, they can exchange routing information. If routes of one router changes, the router sends Update messages carrying only changed routing information to its peers, which greatly reduces bandwidth consumption.

Figure 1 Configuring basic BGP functions

Interfaces 1 through 3 in this example are GE 0/1/0, GE 0/1/8, and GE 0/1/16, respectively.


Device Name

Interface

IP Address

DeviceA

Loopback 0

1.1.1.1/32

GE 0/1/0

172.16.0.1/16

GE 0/1/8

192.168.0.1/24

DeviceB

Loopback 0

2.2.2.2/32

GE 0/1/0

10.1.1.1/24

GE 0/1/8

192.168.0.2/24

GE 0/1/16

10.1.3.1/24

DeviceC

Loopback 0

3.3.3.3/32

GE 0/1/8

10.1.2.1/24

GE 0/1/16

10.1.3.2/24

DeviceD

Loopback 0

4.4.4.4/32

GE 0/1/0

10.1.1.2/24

GE 0/1/8

10.1.2.2/24

Precautions

When configuring basic BGP functions, note the following rules:

  • When establishing a peer relationship, if the specified IP address of the peer is a loopback interface address or a sub-interface address, run the peer connect-interface command on the two ends to ensure that the two ends are correctly connected.

  • If there is no directly connected physical link between EBGP peers, run the peer ebgp-max-hop command to allow EBGP peers to establish TCP connections through multiple hops.

Configuration Roadmap

The configuration roadmap is as follows:

  1. Establish IBGP connections between DeviceB, DeviceC, and DeviceD.

  2. Establish an EBGP connection between DeviceA and DeviceB.

  3. Advertise routes using the network command on DeviceA, and then check the routing tables of DeviceA, DeviceB, and DeviceC.

  4. Configure BGP on DeviceB to import direct routes, and then check the routing tables of DeviceA and DeviceC.

Data Preparation

To complete the configuration, you need the following data:

  • Router ID and AS number of DeviceA

  • Router IDs and AS numbers of DeviceB, DeviceC, and DeviceD

Procedure

  1. Configure an IP address for each interface. For configuration details, see Configuration Files in this section.
  2. Configure OSPF.

    # Configure DeviceB.

    [~DeviceB] ospf 1
[*DeviceB-ospf-1] area 0
[*DeviceB-ospf-1-area-0.0.0.0] network 10.1.1.0 0.0.0.255
[*DeviceB-ospf-1-area-0.0.0.0] network 10.1.3.0 0.0.0.255
[*DeviceB-ospf-1-area-0.0.0.0] network 2.2.2.2 0.0.0.0
[*DeviceB-ospf-1-area-0.0.0.0] commit
[~DeviceB-ospf-1-area-0.0.0.0] quit
[~DeviceB-ospf-1] quit

    # Configure DeviceC.

    [~DeviceC] ospf 1
[*DeviceC-ospf-1] area 0
[*DeviceC-ospf-1-area-0.0.0.0] network 10.1.2.0 0.0.0.255
[*DeviceC-ospf-1-area-0.0.0.0] network 10.1.3.0 0.0.0.255
[*DeviceC-ospf-1-area-0.0.0.0] network 3.3.3.3 0.0.0.0
[*DeviceC-ospf-1-area-0.0.0.0] commit
[~DeviceC-ospf-1-area-0.0.0.0] quit
[~DeviceC-ospf-1] quit

    # Configure DeviceD.

    [~DeviceD] ospf 1
[*DeviceD-ospf-1] area 0
[*DeviceD-ospf-1-area-0.0.0.0] network 10.1.1.0 0.0.0.255
[*DeviceD-ospf-1-area-0.0.0.0] network 10.1.2.0 0.0.0.255
[*DeviceD-ospf-1-area-0.0.0.0] network 4.4.4.4 0.0.0.0
[*DeviceD-ospf-1-area-0.0.0.0] commit
[~DeviceD-ospf-1-area-0.0.0.0] quit
[~DeviceD-ospf-1] quit

  3. Configure IBGP connections.

    # Configure DeviceB.

    [~DeviceB] bgp 65009
[*DeviceB-bgp] router-id 2.2.2.2
[*DeviceB-bgp] peer 3.3.3.3 as-number 65009
[*DeviceB-bgp] peer 4.4.4.4 as-number 65009
[*DeviceB-bgp] peer 3.3.3.3 connect-interface LoopBack0
[*DeviceB-bgp] peer 4.4.4.4 connect-interface LoopBack0
[*DeviceB-bgp] commit
[~DeviceB-bgp] quit

    # Configure DeviceC.

    [~DeviceC] bgp 65009
[*DeviceC-bgp] router-id 3.3.3.3
[*DeviceC-bgp] peer 2.2.2.2 as-number 65009
[*DeviceC-bgp] peer 4.4.4.4 as-number 65009
[*DeviceC-bgp] peer 2.2.2.2 connect-interface LoopBack0
[*DeviceC-bgp] peer 4.4.4.4 connect-interface LoopBack0
[*DeviceC-bgp] commit
[~DeviceC-bgp] quit

    # Configure DeviceD.

    [~DeviceD] bgp 65009
[*DeviceD-bgp] router-id 4.4.4.4
[*DeviceD-bgp] peer 2.2.2.2 as-number 65009
[*DeviceD-bgp] peer 3.3.3.3 as-number 65009
[*DeviceD-bgp] peer 2.2.2.2 connect-interface LoopBack0
[*DeviceD-bgp] peer 3.3.3.3 connect-interface LoopBack0
[*DeviceD-bgp] commit
[~DeviceD-bgp] quit

  4. Configure an EBGP connection.

    # Configure DeviceA.

    [~DeviceA] bgp 65008
[*DeviceA-bgp] router-id 1.1.1.1
[*DeviceA-bgp] peer 192.168.0.2 as-number 65009
[*DeviceA-bgp] commit
[~DeviceA-bgp] quit

    # Configure DeviceB.

    [~DeviceB] bgp 65009
[*DeviceB-bgp] peer 192.168.0.1 as-number 65008
[*DeviceB-bgp] commit
[~DeviceB-bgp] quit

    # Check the status of BGP connections.

    [~DeviceB] display bgp peer
 BGP local router ID : 2.2.2.2
 Local AS number : 65009
 Total number of peers : 3                 Peers in established state : 3
  Peer            V    AS  MsgRcvd  MsgSent  OutQ  Up/Down       State PrefRcv
  3.3.3.3         4 65009        5        5     0 00:44:58 Established       0
  4.4.4.4         4 65009        4        4     0 00:40:54 Established       0
  192.168.0.1     4 65008        3        3     0 00:44:03 Established       0

    The command output shows that DeviceB has established BGP connections with other routers and that the connection status is Established.

  5. Configure DeviceA to advertise the route to 172.16.0.0/16.

    # Configure DeviceA to advertise the route.

    [~DeviceA] bgp 65008
[*DeviceA-bgp] ipv4-family unicast
[*DeviceA-bgp-af-ipv4] network 172.16.0.0 255.255.0.0
[*DeviceA-bgp-af-ipv4] network 192.168.0.0 255.255.255.0
[*DeviceA-bgp-af-ipv4] commit
[~DeviceA-bgp-af-ipv4] quit
[~DeviceA-bgp] quit

    # Check the routing table of DeviceA.

    [~DeviceA] display bgp routing-table
 BGP Local router ID is 1.1.1.1
 Status codes: * - valid, > - best, d - damped, x - best external, a - add path,
               h - history,  i - internal, s - suppressed, S - Stale
               Origin : i - IGP, e - EGP, ? - incomplete
 RPKI validation codes: V - valid, I - invalid, N - not-found
 Total Number of Routes: 1
      Network            NextHop        MED        LocPrf    PrefVal Path/Ogn
 *>   172.16.0.0          0.0.0.0         0                     0      i

    # Check the routing table of DeviceB.

    [~DeviceB] display bgp routing-table
 BGP Local router ID is 2.2.2.2
 Status codes: * - valid, > - best, d - damped, x - best external, a - add path,
               h - history,  i - internal, s - suppressed, S - Stale
               Origin : i - IGP, e - EGP, ? - incomplete
 RPKI validation codes: V - valid, I - invalid, N - not-found
 Total Number of Routes: 1
      Network            NextHop        MED        LocPrf    PrefVal Path/Ogn
 *>   172.16.0.0          192.168.0.1    0                     0      65008i

    # Check the routing table of DeviceC.

    [~DeviceC] display bgp routing-table
 BGP Local router ID is 3.3.3.3
 Status codes: * - valid, > - best, d - damped, x - best external, a - add path,
               h - history,  i - internal, s - suppressed, S - Stale
               Origin : i - IGP, e - EGP, ? - incomplete
 RPKI validation codes: V - valid, I - invalid, N - not-found
 Total Number of Routes: 1
      Network            NextHop        MED        LocPrf    PrefVal Path/Ogn
   i  172.16.0.0          192.168.0.1    0          100        0      65008i

    The command output shows that DeviceC has learned the route to 172.16.0.0 from AS 65008. However, this route is invalid because the next hop 192.168.0.1 is unreachable.

  6. Configure BGP to import direct routes.

    # Configure DeviceB.

    [~DeviceB] bgp 65009
[*DeviceB-bgp] ipv4-family unicast
[*DeviceB-bgp-af-ipv4] import-route direct
[*DeviceB-bgp-af-ipv4] commit
[~DeviceB-bgp-af-ipv4] quit
[~DeviceB-bgp] quit

    # Check the BGP routing table of DeviceA.

    [~DeviceA] display bgp routing-table
 BGP Local router ID is 1.1.1.1
 Status codes: * - valid, > - best, d - damped, x - best external, a - add path,
               h - history,  i - internal, s - suppressed, S - Stale
               Origin : i - IGP, e - EGP, ? - incomplete
 RPKI validation codes: V - valid, I - invalid, N - not-found

 Total Number of Routes: 5
      Network            NextHop        MED        LocPrf    PrefVal Path/Ogn

 *>   2.2.2.2/32         192.168.0.2     0                     0      65009?
 *>   172.16.0.0          0.0.0.0         0                     0      i
 *>   10.1.1.0/24        192.168.0.2     0                     0      65009?
 *>   10.1.3.0/24        192.168.0.2     0                     0      65009?
 *>   192.168.0.0        192.168.0.2     0                     0      65009?

    # Check the BGP routing table of DeviceC.

    [~DeviceC] display bgp routing-table
 BGP Local router ID is 3.3.3.3
 Status codes: * - valid, > - best, d - damped, x - best external, a - add path,
               h - history,  i - internal, s - suppressed, S - Stale
               Origin : i - IGP, e - EGP, ? - incomplete
 RPKI validation codes: V - valid, I - invalid, N - not-found

 Total Number of Routes: 5
      Network            NextHop        MED        LocPrf    PrefVal Path/Ogn

   i  2.2.2.2/32         2.2.2.2         0          100        0      ?
 *>i  10.1.1.0/24        2.2.2.2         0          100        0      ?
 * i  10.1.3.0/24        2.2.2.2         0          100        0      ?
 *>i  172.16.0.0         192.168.0.1     0          100        0      65008i
 *>i  192.168.0.0        2.2.2.2         0          100        0      ?

    The command output shows that the route to 172.16.0.0 becomes valid and that the next hop is the address of DeviceA.

    # Verify the configuration using the ping command.

    [~DeviceC] ping 172.16.0.1
  PING 172.16.0.1: 56  data bytes, press CTRL_C to break
    Reply from 172.16.0.1: bytes=56 Sequence=1 ttl=254 time=31 ms
    Reply from 172.16.0.1: bytes=56 Sequence=2 ttl=254 time=47 ms
    Reply from 172.16.0.1: bytes=56 Sequence=3 ttl=254 time=31 ms
    Reply from 172.16.0.1: bytes=56 Sequence=4 ttl=254 time=16 ms
    Reply from 172.16.0.1: bytes=56 Sequence=5 ttl=254 time=31 ms
  --- 172.16.0.1 ping statistics ---
    5 packet(s) transmitted
    5 packet(s) received
    0.00% packet loss
    round-trip min/avg/max = 16/31/47 ms

Configuration Files

  • DeviceA configuration file

    #
sysname DeviceA
#
interface GigabitEthernet0/1/0
 undo shutdown
 ip address 172.16.0.1 255.255.0.0
#
interface GigabitEthernet0/1/8
 undo shutdown
 ip address 192.168.0.1 255.255.255.0
#
interface LoopBack0
 ip address 1.1.1.1 255.255.255.255
#
bgp 65008
 router-id 1.1.1.1
 peer 192.168.0.2 as-number 65009
 #
 ipv4-family unicast
  undo synchronization 
  network 172.16.0.0 255.255.0.0
  network 192.168.0.0 255.255.255.0
  peer 192.168.0.2 enable
#
return

  • DeviceB configuration file

    sysname DeviceB
#
interface GigabitEthernet0/1/0
 undo shutdown
 ip address 10.1.1.1 255.255.255.0
#
interface GigabitEthernet0/1/8
 undo shutdown
 ip address 192.168.0.2 255.255.255.0
#
interface GigabitEthernet0/1/16
 undo shutdown
 ip address 10.1.3.1 255.255.255.0
#
interface LoopBack0
 ip address 2.2.2.2 255.255.255.255
#
bgp 65009
 router-id 2.2.2.2
 peer 3.3.3.3 as-number 65009
 peer 3.3.3.3 connect-interface LoopBack0
 peer 4.4.4.4 as-number 65009
 peer 4.4.4.4 connect-interface LoopBack0
 peer 192.168.0.1 as-number 65008
#
 ipv4-family unicast
  undo synchronization 
  import-route direct
  peer 3.3.3.3 enable
  peer 4.4.4.4 enable 
  peer 192.168.0.1 enable
#
ospf 1
 area 0.0.0.0
  network 2.2.2.2 0.0.0.0
  network 10.1.1.0 0.0.0.255
  network 10.1.3.0 0.0.0.255
#
return

  • DeviceC configuration file

    #
sysname DeviceC
#
interface GigabitEthernet0/1/8
 undo shutdown
 ip address 10.1.2.1 255.255.255.0
#
interface GigabitEthernet0/1/16
 undo shutdown
 ip address 10.1.3.2 255.255.255.0
#
interface LoopBack0
 ip address 3.3.3.3 255.255.255.255
#
bgp 65009
 router-id 3.3.3.3
 peer 2.2.2.2. as-number 65009
 peer 2.2.2.2 connect-interface LoopBack0
 peer 4.4.4.4 as-number 65009
 peer 4.4.4.4 connect-interface LoopBack0
 #
 ipv4-family unicast
  undo synchronization 
  peer 2.2.2.2 enable
  peer 4.4.4.4 enable
#
ospf 1
 area 0.0.0.0
  network 3.3.3.3 0.0.0.0
  network 10.1.2.0 0.0.0.255
  network 10.1.3.0 0.0.0.255
#
return

  • DeviceD configuration file

    #
sysname DeviceD
#
interface GigabitEthernet0/1/0
 undo shutdown
 ip address 10.1.1.2 255.255.255.0
#
interface GigabitEthernet0/1/8
 undo shutdown
 ip address 10.1.2.2 255.255.255.0
#
interface LoopBack0
 ip address 4.4.4.4 255.255.255.255
#
bgp 65009
 router-id 4.4.4.4
 peer 2.2.2.2 as-number 65009
 peer 2.2.2.2 connect-interface LoopBack0
 peer 3.3.3.3 as-number 65009
 peer 3.3.3.3 connect-interface LoopBack0
 #
 ipv4-family unicast
  undo synchronization 
  peer 2.2.2.2 enable
  peer 3.3.3.3 enable
#
ospf 1
 area 0.0.0.0
  network 4.4.4.4 0.0.0.0
  network 10.1.1.0 0.0.0.255
  network 10.1.2.0 0.0.0.255
#
return
Parent Topic: Configuration Examples for BGP
Copyright © Huawei Technologies Co., Ltd.
Copyright © Huawei Technologies Co., Ltd.
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