Example for Configuring BGP Route Dampening

Configuring BGP route dampening can improve network stability.

Networking Requirements

In Figure 1, all routers are configured with BGP; Device A resides in AS 100; Device B resides in AS 200; Device C resides in AS 300; Device D resides in AS 400. EBGP runs between Device C and Device A, between Device C and Device B, and between Device C and Device D. For routes from different EBGP neighbors, Device C applies different route dampening policies. It is required that BGP route dampening be configured to suppress unstable routes and improve network stability.

Figure 1 Configuring BGP route dampening

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

Precautions

When configuring BGP route dampening, note the following rules:

BGP route dampening takes effect only on EBGP routes.
Set a small MaxSuppressTime for routes with the small masks.

Configuration Roadmap

The configuration roadmap is as follows:

Establish EBGP connections between Device A and Device C, between Device B and Device C, and between Device D and Device C.
Configure route dampening policies on Device C and then check routes.

Data Preparation

To complete the configuration, you need the following data:

Router IDs and AS numbers of Device A, Device B, Device C, and Device D
Name of the route flap dampening policy to be applied to Device C

Procedure

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

Configure BGP connections.

# Configure Device A.

[~DeviceA] bgp 100
[*DeviceA-bgp] router-id 1.1.1.1
[*DeviceA-bgp] peer 10.10.1.2 as-number 300
[*DeviceA-bgp] ipv4-family unicast
[*DeviceA-bgp-af-ipv4] network 172.16.1.0 24
[*DeviceA-bgp-af-ipv4] commit
[~DeviceA-bgp-af-ipv4] quit
[~DeviceA-bgp] quit

# Configure Device B.

[~DeviceB] bgp 200
[*DeviceB-bgp] router-id 2.2.2.2
[*DeviceB-bgp] peer 10.10.2.2 as-number 300
[*DeviceB-bgp] ipv4-family unicast
[*DeviceB-bgp-af-ipv4] network 192.168.1.0 24
[*DeviceB-bgp-af-ipv4] commit
[~DeviceB-bgp-af-ipv4] quit
[~DeviceB-bgp] quit

# Configure Device C.

[~DeviceC] bgp 300
[*DeviceC-bgp] router-id 3.3.3.3
[*DeviceC-bgp] peer 10.10.1.1 as-number 100
[*DeviceC-bgp] peer 10.10.2.1 as-number 200
[*DeviceC-bgp] peer 10.10.3.1 as-number 400
[*DeviceC-bgp] commit
[~DeviceC-bgp] quit

# Configure Device D.

[~DeviceD] bgp 400
[*DeviceD-bgp] router-id 4.4.4.4
[*DeviceD-bgp] peer 10.10.3.2 as-number 300
[*DeviceD-bgp] commit
[~DeviceD-bgp] quit

# Check the BGP peers of Device C.

[*DeviceC] display bgp peer

 BGP local router ID : 3.3.3.3
 Local AS number : 300
 Total number of peers : 3         Peers in established state : 3

  Peer            V          AS  MsgRcvd  MsgSent  OutQ  Up/Down       State  PrefRcv
  10.10.1.1       4         100        3        3     0 00:00:01 Established    0
  10.10.2.1       4         200        3        3     0 00:00:00 Established    0
  10.10.3.1       4         400        3        3     0 00:00:01 Established    0

The command output shows that the BGP connection status of with each peer is Established.

Configure BGP route dampening policies.

# Configure an IP prefix list named prefix-a on Device C to accept only the routes with prefix 172.16.1.0/24.

[~DeviceC] ip ip-prefix prefix-a index 10 permit 172.16.1.0 24
[*DeviceC] commit

# Configure an IP prefix list named prefix-b on Device C to accept only the routes with prefix 192.168.1.0/24.

[~DeviceC] ip ip-prefix prefix-b index 20 permit 192.168.1.0 24
[*DeviceC] commit

# Configure a route-policy named dampen-policy on Device C and then apply different route dampening policies to the routes with different prefix lengths.

[~DeviceC] route-policy dampen-policy permit node 10
[*DeviceC-route-policy] if-match ip-prefix prefix-a
[*DeviceC-route-policy] apply dampening 10 1000 2000 5000
[*DeviceC-route-policy] commit
[~DeviceC-route-policy] quit
[*DeviceC] route-policy dampen-policy permit node 20
[*DeviceC-route-policy] if-match ip-prefix prefix-b
[*DeviceC-route-policy] apply dampening 10 800 3000 10000
[*DeviceC-route-policy] commit
[~DeviceC-route-policy] quit

# Apply route dampening policies to the routes that flap.

[*DeviceC] bgp 300
[*DeviceC-bgp] ipv4-family unicast
[*DeviceC-bgp-af-ipv4] dampening route-policy dampen-policy
[*DeviceC-bgp-af-ipv4] commit
[~DeviceC-bgp] quit

# Check the configured route dampening parameters on Device C.

[~DeviceC] display bgp routing-table dampening parameter

 Maximum Suppress Time(in second) : 3973
 Ceiling Value                    : 16000
 Reuse Value                      : 750
 HalfLife Time(in  second)        : 900
 Suppress-Limit                   : 2000
 Route-policy                     : dampen-policy

Configuration Files

Device A configuration file

#
sysname DeviceA
#
interface GigabitEthernet0/1/0
 undo shutdown
 ip address 10.10.1.1 255.255.255.0
#
interface GigabitEthernet0/1/8
 undo shutdown
 ip address 172.16.1.1 255.0.0.0
#
bgp 100
 router-id 1.1.1.1
 peer 10.10.1.2 as-number 300
 #
 ipv4-family unicast
  undo synchronization 
  network 172.16.1.0 255.255.255.0
  peer 10.10.1.2 enable
#
return

Device B configuration file

#
sysname DeviceB
#
interface GigabitEthernet0/1/0
 undo shutdown
 ip address 10.10.2.1 255.255.255.0
#
interface GigabitEthernet0/1/8
 undo shutdown
 ip address 192.168.1.1 255.255.255.0
#
bgp 200
 router-id 2.2.2.2
 peer 10.10.2.2 as-number 300
 #
 ipv4-family unicast
  undo synchronization 
  network 192.168.1.0 255.255.255.0
  peer 10.10.2.2 enable
#
return

Device C configuration file

#
sysname DeviceC
#
interface GigabitEthernet0/1/0
 undo shutdown
 ip address 10.10.1.2 255.255.255.0
#
interface GigabitEthernet0/1/8
 undo shutdown
 ip address 10.10.2.2 255.255.255.0
#
interface GigabitEthernet0/1/16
 undo shutdown
 ip address 10.10.3.2 255.255.255.0
#
bgp 300
 router-id 3.3.3.3
 peer 10.10.1.1 as-number 100
 peer 10.10.2.1 as-number 200
 peer 10.10.3.1 as-number 400
 #
 ipv4-family unicast
  undo synchronization 
  dampening route-policy dampen-policy
  peer 10.10.1.1 enable
  peer 10.10.2.1 enable
  peer 10.10.3.1 enable
#
route-policy dampen-policy permit node 10
 if-match ip-prefix prefix-a
 apply dampening 10 1000 2000 5000
#
route-policy dampen-policy permit node 20
 if-match ip-prefix prefix-b
 apply dampening 10 800 3000 10000
#
ip ip-prefix prefix-a index 10 permit 8.0.0.0 8
#
ip ip-prefix prefix-b index 20 permit 9.1.1.0 24
#
return

Device D configuration file

#
sysname DeviceD
#
interface GigabitEthernet0/1/8
 undo shutdown
 ip address 10.10.3.1 255.255.255.0
#
bgp 400
 router-id 4.4.4.4
 peer 10.10.3.2 as-number 300
 #
 ipv4-family unicast
  undo synchronization 
  peer 10.10.3.2 enable
#
return