Example for Configuring OSPF Fast Convergence

This section describes how to configure OSPF fast convergence by adjusting the timer parameter and configuring BFD.

Networking Requirements

On the network shown in Figure 1, on the broadcast network, OSPF runs on the four devices, which belong to the same OSPF area.

Figure 1 Networking for configuring OSPF fast convergence

Interface 1 in this example represents GE 0/1/0.



Precautions

When configuring OSPF fast convergence, note the following rules:

  • You can decrease the interval at which Hello packets are sent and values of the Dead, Poll, and Wait timers for fast OSPF network convergence. Frequent packet transmission, however, may overload the device. In addition, the OSPF network convergence slows down if the values of these timers are too large. Therefore, set values based on the network stability.

  • The intervals at which Hello packets are sent and values of the Dead, Poll, and Wait timers at both ends must be the same. Otherwise, the OSPF neighbor relationship cannot be established.

Configuration Roadmap

The configuration roadmap is as follows:

  1. Configure basic OSPF functions on each router for interconnection.

  2. Configure the BFD function on each router.

  3. Adjust the holddown time of the OSPF neighbors on each router.

  4. Configure the Smart-discover function on each router.

  5. Adjust the intervals for configuration update, LSA reception, and SPF calculation through an intelligent timer on each router.

Data Preparation

To complete the configuration, you need the following data.

  • Holddown time of the OSPF neighbors

  • Intervals for LSA update, LSA reception, and SPF calculation

Procedure

  1. Assign an IP address to each interface. For configuration details, see Configuration Files in this section.
  2. Configure basic OSPF functions. For details, see Example for Configuring Basic OSPF Functions.
  3. Adjust the holddown time of the OSPF neighbors on each router.

    # Configure Device A.

    [~DeviceA] interface gigabitethernet 0/1/0
[*DeviceA-GigabitEthernet0/1/0] ospf timer dead 30
[*DeviceA-GigabitEthernet0/1/0] commit

    • The holddown time of neighbors of the OSPF-capable interfaces must be longer than the interval at which Hello packets are sent, and the values of dead interval on the routers in the same network segment must be the same.

    • In this configuration example, the following configurations on each router are the same as that on Device A. For configuration details, see "Configuration Files" in this section.

      • Adjust the holddown time of the OSPF neighbors on each router.

      • Configure the Smart-discover function on each router.

      • Adjust the intervals for configuration update, LSA reception, and SPF calculation through an intelligent timer on the router.

  4. Configure the Smart-discover function on each router.

    # Configure Device A.

    [*DeviceA-GigabitEthernet0/1/0] ospf smart-discover
[*DeviceA-GigabitEthernet0/1/0] commit
[~DeviceA-GigabitEthernet0/1/0] quit

  5. Configure the BFD function on each router.

    # Configure Device A.

    [*DeviceA] bfd
[*DeviceA-bfd] quit
[*DeviceA] ospf
[*DeviceA-ospf-1] bfd all-interfaces enable
[*DeviceA-ospf-1] commit
[~DeviceA-ospf-1] quit

  6. Adjust the intervals for configuration update, LSA reception, and SPF calculation through an intelligent timer on each router.

    # Configure Device A.

    [~DeviceA] ospf 1
[*DeviceA-ospf-1] lsa-originate-interval intelligent-timer 3000 200 500
[*DeviceA-ospf-1] lsa-arrival-interval intelligent-timer 3000 200 500
[*DeviceA-ospf-1] spf-schedule-interval intelligent-timer 3000 200 500
[*DeviceA-ospf-1] commit

  7. Verify the configuration.

    # Run the display ospf brief command on each router to view the brief information about OSPF. Use Router A as an example. You can view the value of timers.

    [~DeviceA] display ospf brief
          OSPF Process 1 with Router ID 9.9.9.9
                  OSPF Protocol Information
RouterID: 9.9.9.9          Border Router: AREA 
Multi-VPN-Instance is not enabled 
Global DS-TE Mode: Non-Standard IETF Mode 
Graceful-restart capability: disabled 
Helper support capability  : not configured 
OSPF Stub Router State Reason: Startup Synchronize
    Router LSA stub links with cost 65535
    Summary LSA with cost 16777214 
    External LSA with cost 16777214 
Applications Supported: MPLS Traffic-Engineering 
Spf-schedule-interval: max 10000ms, start 500ms, hold 1000ms 
Default ASE parameters: Metric: 1 Tag: 1 Type: 2 
Route Preference: 10 
ASE Route Preference: 150 
Intra Route Preference: 50 
Inter Route Preference: 50 
SPF Computation Count: 56 
RFC 1583 Compatible 
Retransmission limitation is disabled 
bfd enabled 
BFD Timers: Tx-Interval 10 , Rx-Interval 10 , Multiplier 3 
Area Count: 2   Nssa Area Count: 0 
ExChange/Loading Neighbors: 0

 Area: 0.0.0.0             MPLS TE not enabled
 Authtype: None   Area flag: Normal
 SPF scheduled count: 2
 Exchange/Loading neighbors: 0
 Router ID conflict state: Normal

 Interface: 1.1.1.1 (GE0/1/17)
 Cost: 1       State: DR      Type: Broadcast      MTU: 1500
 Priority: 1
 Designated Router: 1.1.1.1
 Backup Designated Router: 0.0.0.0
 Timers: Hello 10, Dead 40, Wait 40, Poll 120, Retransmit 5, Transmit Delay 1

Configuration Files

  • Device A configuration file

    #
 sysname DeviceA
#
router id 1.1.1.1
#
 bfd
#
interface GigabitEthernet0/1/0
 undo shutdown
 ip address 192.168.1.1 255.255.255.0
 ospf timer dead 30
 ospf smart-discover 
#
ospf 1
 bfd all-interfaces enable
 spf-schedule-interval intelligent-timer 3000 200 500
 lsa-arrival-interval intelligent-timer 3000 200 500
 lsa-originate-interval intelligent-timer 3000 200 500
 area 0.0.0.0
  network 192.168.1.0 0.0.0.255
#
return

  • Device B configuration file

    #
 sysname DeviceB
#
router id 2.2.2.2
#
 bfd
#
interface GigabitEthernet0/1/0
 undo shutdown
 ip address 192.168.1.2 255.255.255.0
 ospf timer dead 30
 ospf smart-discover 
#
ospf 1
 bfd all-interfaces enable
 spf-schedule-interval intelligent-timer 3000 200 500
 lsa-arrival-interval intelligent-timer 3000 200 500
 lsa-originate-interval intelligent-timer 3000 200 500
 area 0.0.0.0
  network 192.168.1.0 0.0.0.255
#
return

  • Device C configuration file

    #
 sysname DeviceC
#
router id 3.3.3.3
#
 bfd
#
interface GigabitEthernet0/1/0
 undo shutdown
 ip address 192.168.1.3 255.255.255.0
 ospf timer dead 30
 ospf smart-discover 
#
ospf 1
 bfd all-interfaces enable
 spf-schedule-interval intelligent-timer 3000 200 500
 lsa-arrival-interval intelligent-timer 3000 200 500
 lsa-originate-interval intelligent-timer 3000 200 500
 area 0.0.0.0
  network 192.168.1.0 0.0.0.255
#
return

  • Device D configuration file

    #
 sysname DeviceD
#
router id 4.4.4.4
#
 bfd
#
interface GigabitEthernet0/1/0
 undo shutdown
 ip address 192.168.1.4 255.255.255.0
 ospf timer dead 30
 ospf smart-discover 
#
ospf 1
 bfd all-interfaces enable
 spf-schedule-interval intelligent-timer 3000 200 500
 lsa-arrival-interval intelligent-timer 3000 200 500
 lsa-originate-interval intelligent-timer 3000 200 500
 area 0.0.0.0
  network 192.168.1.0 0.0.0.255
#
return
Parent Topic: Configuration Examples for OSPF
Copyright © Huawei Technologies Co., Ltd.
Copyright © Huawei Technologies Co., Ltd.
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