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Example: Configuring BGP Route Flap Damping Based on the MBGP MVPN Address Family

Requirements

This example uses Junos OS Release 12.2. BGP route flap damping support for MBGP MVPN, specifically, and on an address family basis, in general, is introduced in Junos OS Release 12.2.

Overview

BGP route flap damping helps to diminish route instability caused by routes being repeatedly withdrawn and readvertised when a link is intermittently failing.

This example uses the default damping parameters and demonstrates an MBGP MVPN scenario with three provider edge (PE) routing devices, three customer edge (CE) routing devices, and one provider (P) routing device.

Figure 1 shows the topology used in this example.

Figure 1: MBGP MVPN with BGP Route Flap Damping

On PE Device R4, BGP route flap damping is configured for address family inet-mvpn. A routing policy called dampPolicy uses the nlri-route-type match condition to damp only MVPN route types 3, 4, and 5. All other MVPN route types are not damped.

This example shows the full configuration on all devices in the CLI Quick Configuration section. The Configuring Device R4 section shows the step-by-step configuration for PE Device R4.

Configuration

CLI Quick Configuration

To quickly configure this example, copy the following commands, paste them into a text file, remove any line breaks, change any details necessary to match your network configuration, and then copy and paste the commands into the CLI at the [edit] hierarchy level.

Configuring Device R4

Step-by-Step Procedure

1. Configure the interfaces.

   [edit interfaces]user@R4# set ge-1/2/0 unit 10 family inet address 10.1.1.10/30user@R4# set ge-1/2/0 unit 10 family mpls
   user@R4# set ge-1/2/1 unit 17 family inet address 10.1.1.17/30user@R4# set ge-1/2/1 unit 17 family mpls
   user@R4# set vt-1/2/0 unit 4 family inet
   user@R4# set lo0 unit 4 family inet address 1.1.1.4/32
   user@R4# set lo0 unit 104 family inet address 100.1.1.4/32

2. Configure MPLS and the signaling protocols on the interfaces.

   [edit protocols]user@R4# set mpls interface alluser@R4# set mpls interface ge-1/2/0.10
   user@R4# set rsvp interface all aggregate
   user@R4# set ldp interface ge-1/2/0.10user@R4# set ldp p2mp

3. Configure BGP.

   The BGP configuration enables BGP route flap damping for the inet-mvpn address family. The BGP configuration also imports into the routing table the routing policy called dampPolicy. This policy is applied to neighbor PE Device R2.

   [edit protocols bgp group ibgp]user@R4# set type internaluser@R4# set local-address 1.1.1.4user@R4# set family inet-vpn unicastuser@R4# set family inet-vpn anyuser@R4# set family inet-mvpn signaling dampinguser@R4# set neighbor 1.1.1.2 import dampPolicyuser@R4# set neighbor 1.1.1.5

4. Configure an interior gateway protocol.

   [edit protocols ospf]user@R4# set traffic-engineering
   [edit protocols ospf area 0.0.0.0]user@R4# set interface alluser@R4# set interface lo0.4 passiveuser@R4# set interface ge-1/2/0.10

5. Configure a damping policy that uses the nlri-route-type match condition to damp only MVPN route types 3, 4, and 5.

   [edit policy-options policy-statement dampPolicy term term1]user@R4# set from family inet-mvpnuser@R4# set from nlri-route-type 3user@R4# set from nlri-route-type 4user@R4# set from nlri-route-type 5user@R4# set then accept
   

6. Configure the damping policy to disable BGP route flap damping.

   The no-damp policy (damping no-damp disable) causes any damping state that is present in the routing table to be deleted. The then damping no-damp statement applies the no-damp policy as an action and has no from match conditions. Therefore, all routes that are not matched by term1 are matched by this term, with the result that all other MVPN route types are not damped.

   [edit policy-options policy-statement dampPolicy]user@R4# set then damping no-dampuser@R4# set then accept
   [edit policy-options]user@R4# set damping no-damp disable

7. Configure the parent_vpn_routes to accept all other BGP routes that are not from the inet-mvpn address family.

   This policy is applied as an OSPF export policy in the routing instance.

   [edit policy-options policy-statement parent_vpn_routes]user@R4# set from protocol bgpuser@R4# set then accept
   

8. Configure the VPN routing and forwarding (VRF) instance.

   [edit routing-instances vpn-1]user@R4# set instance-type vrfuser@R4# set interface vt-1/2/0.4user@R4# set interface ge-1/2/1.17user@R4# set interface lo0.104user@R4# set route-distinguisher 100:100user@R4# set vrf-target target:1:1
   user@R4# set protocols ospf export parent_vpn_routesuser@R4# set protocols ospf area 0.0.0.0 interface lo0.104 passiveuser@R4# set protocols ospf area 0.0.0.0 interface ge-1/2/1.17
   user@R4# set protocols pim rp static address 100.1.1.2user@R4# set protocols pim interface ge-1/2/1.17 mode sparse
   user@R4# set protocols mvpn

9. Configure the router ID and the autonomous system (AS) number.

   [edit routing-instances vpn-A]user@R4# set routing-options router-id 1.1.1.4user@R4# set routing-options autonomous-system 1001

10. If you are done configuring the device, commit the configuration.

    user@R4# commit

Results

From configuration mode, confirm your configuration by entering the show interfaces, show protocols, show routing-instances, and show routing-options commands. If the output does not display the intended configuration, repeat the instructions in this example to correct the configuration.

Verification

Confirm that the configuration is working properly.

• Verifying That Route Flap Damping Is Disabled
• Verifying Route Flap Damping

Verifying That Route Flap Damping Is Disabled

Purpose

Verify the presence of the no-damp policy, which disables damping for MVPN route types other than 3, 4, and 5.

Action

From operational mode, enter the show policy damping command.

Default damping information:
  Halflife: 15 minutes
  Reuse merit: 750 Suppress/cutoff merit: 3000
  Maximum suppress time: 60 minutes
  Computed values:
    Merit ceiling: 12110
    Maximum decay: 6193
Damping information for "no-damp":
  Damping disabled

Meaning

The output shows that the default damping parameters are in effect and that the no-damp policy is also in effect for the specified route types.

Verifying Route Flap Damping

Purpose

Check whether BGP routes have been damped.

Action

From operational mode, enter the show bgp summary command.

Groups: 1 Peers: 2 Down peers: 0
Table          Tot Paths  Act Paths Suppressed    History Damp State    Pending
bgp.l3vpn.0          
                       6          6          0          0          0          0
bgp.l3vpn.2          
                       0          0          0          0          0          0
bgp.mvpn.0           
                       2          2          0          0          0          0
Peer                     AS      InPkt     OutPkt    OutQ   Flaps Last Up/Dwn State|#Active/Received/Accepted/Damped...
1.1.1.2                1001       3159       3155       0       0    23:43:47 Establ
  bgp.l3vpn.0: 3/3/3/0
  bgp.l3vpn.2: 0/0/0/0
  bgp.mvpn.0: 1/1/1/0
  vpn-1.inet.0: 3/3/3/0
  vpn-1.mvpn.0: 1/1/1/0
1.1.1.5                1001       3157       3154       0       0    23:43:40 Establ
  bgp.l3vpn.0: 3/3/3/0
  bgp.l3vpn.2: 0/0/0/0
  bgp.mvpn.0: 1/1/1/0
  vpn-1.inet.0: 3/3/3/0
  vpn-1.mvpn.0: 1/1/1/0

Meaning

When Damp State field shows that zero routes in the bgp.mvpn.0 routing table have been damped. Further down, the last number in the State field shows that zero routes have been damped for BGP peer 1.1.1.2.