On an ospf network what are the default intervals for the hello, dead, wait, and retransmit timers?

Adjusting the OSPF Network Convergence Speed

By adjusting OSPF timers, you can implement OSPF network convergence speed.

Pre-configuration Tasks

Before adjusting the OSPF network convergence speed, complete the following tasks:

• Configure a link layer protocol.

• Configure IP addresses for interfaces to ensure that neighboring nodes are reachable at the network layer.

• Configure basic OSPF functions.

Configuration Procedures

Perform one or more of the following configurations as required.

• Setting the Interval at Which Hello Packets Are Sent
  You can adjust the value of the Hello timer to change the speed of the OSPF neighbor relationship establishment and change the network convergence speed.
• Setting the delay for transmitting LSAs on an interface
  This configuration is important for low-speed networks.
• Setting the Dead Time of an OSPF neighbor
  If no Hello packet is received from a neighbor within a dead interval, the neighbor is considered Down.
• Configuring OSPF Sham Hello
  With OSPF sham hello, device can exchange Hello and LSU and LSAck packets to maintain OSPF neighbor relationships, which strengthens the neighbor detection mechanism.
• Configuring Smart-discover
  After Smart-discover is configured, when the neighbor status changes or the DR or BDR on the multiple-access network (broadcast network or NBMA network) changes, the local router sends Hello packets to its neighbor immediately without waiting for the Hello timer to expire.
• Setting the Interval at Which LSAs Are Updated
  You can set the interval at which LSAs are updated based on network connections and router resources.
• Setting the Interval at Which LSAs Are Received
  You can set the interval at which LSAs are received based on network connections and router resources.
• Setting the Interval for the SPF Calculation
  By setting the interval for the SPF calculation, you can save resources consumed by frequent network changes.
• Configuring the Function to Suppress the Advertisement of Interface Addresses
  This section describes how to configure the function to suppress the advertisement of interface addresses so that interface addresses can be reused.
• Configuring the Route Calculation Delay Function to Suppress Frequent LSA Flapping
  A route calculation delay can suppress frequent OSPF LSA flapping.
• Disabling Master/Slave Board Switching Triggered by Abnormal OSPF LSA Aging
  By default, master/slave board switching triggered by abnormal OSPF LSA aging is enabled. To disable this function, perform this task.
• Disabling OSPF LSA Aging Management
  By default, the OSPF LSA aging management function is enabled. To disable this function, perform this task.
• Setting a Period During Which OSPF Keeps the Maximum Cost in Local LSAs
  If a period during which OSPF keeps the maximum cost in local LSAs is configured and an OSPF interface changes from Down to Up, traffic is switched back only when the period elapses.
• Configuring Secure Synchronization
  Secure synchronization prevents traffic loss after a device is restarted.
• Verifying the Configuration of the OSPF Network Convergence Speed
  After configuring OSPF fast network convergence, verify OSPF brief information.

Setting the Interval at Which Hello Packets Are Sent

You can adjust the value of the Hello timer to change the speed of the OSPF neighbor relationship establishment and change the network convergence speed.

Context

Hello packets are periodically sent between OSPF interfaces to establish and maintain neighbor relationships. The intervals set on the interfaces at both ends must be the same. Otherwise, the OSPF neighbor relationship cannot be established.

Procedure

1. Run system-view

   The system view is displayed.

2. Run interface interface-type interface-number

   The OSPF interface view is displayed.

3. Run ospf timer hello interval [ conservative ]

   The interval at which Hello packets are sent is set on the OSPF interface.

   If the conservative parameter is specified in the command, the conservative mode is configured for the dead timer. If the conservative mode is configured, the value configured for the dead timer using the ospf timer dead command takes effect even when the value is less than 10s.

   To speed up OSPF convergence in the case of a link failure, configuring BFD For OSPF is recommended. If the remote end does not support BFD for OSPF or you do not want to configure BFD for OSPF, specify conservative when you run the ospf timer hello command. If the conservative mode is configured, the value configured for the dead timer using the ospf timer dead command takes effect even when the value is less than 10s; if the value configured for the dead timer is greater than 10s, services may be affected.

   NOTE:

   The interval must be longer than the time a device takes to perform a master/slave main control board switchover. If the timer is set to less than the switchover time, a protocol intermittent interruption occurs during a switchover. The default timer value is recommended.

4. Run commit

   The configuration is committed.

Setting the delay for transmitting LSAs on an interface

This configuration is important for low-speed networks.

Procedure

1. Run system-view

   The system view is displayed.

2. Run interface interface-type interface-number

   The OSPF interface view is displayed.

3. Run ospf trans-delay interval

   The delay for transmitting LSAs is set on an interface.

   The LSAs in the LSDB of the local router age with time (increase by 1 each second), but not during transmission. To set a delay for transmitting LSAs on an interface.

4. Run commit

   The configuration is committed.

Setting the Dead Time of an OSPF neighbor

If no Hello packet is received from a neighbor within a dead interval, the neighbor is considered Down.

Procedure

1. Run system-view

   The system view is displayed.

2. Run interface interface-type interface-number

   The OSPF interface view is displayed.

3. Run ospf timer dead interval

   The dead time is set for the neighbor relationship.

   By default, the dead time of the neighbor relationship on a P2P or broadcast interface is 40s; the dead time of the neighbor relationship on a P2MP or NBMA interface is 120s; the dead time of the neighbor relationship on the same interface is four times the interval at which Hello packets are sent.

   NOTE:

   If the dead interval of an OSPF neighbor is shorter than 10s, the session may be closed. Therefore, if dead interval is shorter than 10s, the actual dead interval of an OSPF neighbor is not shorter than 10s. If the conservative mode is configured using the ospf timer hello command, the configured dead timer takes effect even when its value is less than 10s.

   Both the Hello timer and Dead timer are restored to the default values if the network type is changed.

4. Run commit

   The configuration is committed.

Configuring OSPF Sham Hello

With OSPF sham hello, device can exchange Hello and LSU and LSAck packets to maintain OSPF neighbor relationships, which strengthens the neighbor detection mechanism.

Procedure

1. Run system-view

   The system view is displayed.

2. Run ospf [ process-id ]

   The OSPF process view is displayed.

3. Run sham-hello enable

   OSPF sham hello is enabled.

4. Run commit

   The configuration is committed.

Configuring Smart-discover

After Smart-discover is configured, when the neighbor status changes or the DR or BDR on the multiple-access network (broadcast network or NBMA network) changes, the local router sends Hello packets to its neighbor immediately without waiting for the Hello timer to expire.

Context

Without Smart-discover, when the neighbor status of the NE changes or the DR/BDR on the multiple-access network (broadcast or NBMA network) changes, the NE does not send Hello packets to its neighbor until the Hello timer expires; after Smart-discover is configured, the NE sends Hello packets to its neighbor immediately without waiting for the Hello timer to expire, which speeds up the neighbor relationship establishment and OSPF network convergence.

Procedure

1. Run system-view

   The system view is displayed.

2. Run interface interface-type interface-number

   The OSPF interface view is displayed.

3. Run ospf smart-discover

   Smart-discover is configured on the interface.

4. Run commit

   The configuration is committed.

Setting the Interval at Which LSAs Are Updated

You can set the interval at which LSAs are updated based on network connections and router resources.

Context

OSPF sets the interval at which LSAs are updated to 5s. This prevents network connections or frequent route flapping from consuming excessive network bandwidth or device resources. On a stable network that requires fast route convergence, you can change the interval for updating LSAs to 0s. In this manner, the device can fast respond to topology or route changes, which speeds up route convergence.

Procedure

1. Run system-view

   The system view is displayed.

2. Run ospf [ process-id ]

   The OSPF process view is displayed.

3. Run lsa-originate-interval { 0 | intelligent-timer max-interval start-interval hold-interval [ other-type interval ] | other-type interval [ intelligent-timer max-interval start-interval hold-interval ] }

   The interval at which LSAs are updated is set.

   • intelligent-timer: Sets the intelligent timer to update OSPF Type-1 LSA (Router LSA) , Type-2 LSA (Network LSA), Type-5 LSA (AS-external-LSA), Type-7 LSA (NSSA LSA).
   • max-interval: Sets the maximum interval at which LSAs are updated, in milliseconds.
   • start-interval: Sets the initial interval at which LSAs are updated, in milliseconds.
   • hold-interval: Sets the hold interval at which LSAs are updated, in milliseconds.
   • other-type: Sets the interval to update OSPF Type-3 LSA (Network-summary-LSA), Type-4 LSA (ASBR-summary-LSA) and Type-10 LSA (Opaque LSA).

   After an intelligent timer is enabled, the interval for updating LSAs is as follows:

   1. The initial interval for updating LSAs is specified by start-interval.
   2. The interval for updating LSAs for the nth (n≥2) time equal hold-interval x 2(n-2).
   3. When the interval specified by hold-interval x 2(n-2) reaches the maximum interval specified by max-interval, OSPF updates LSAs at the maximum interval for three consecutive times. Then, OSPF updates LSAs at the initial interval specified by start-interval.

4. (Optional) Run lsa-originate-interval suppress-flapping suppress-interval [ threshold threshold ]

   The suppression period that takes effect when the OSPF LSAs to be sent flap is configured.

   If no flapping occurs among the OSPF LSAs to be sent, the configuration of the lsa-originate-interval command prevents the device from frequently sending LSAs. If the OSPF LSAs to be sent flap, the configuration of the lsa-originate-interval suppress-flapping command minimizes the impact of the flapping on services. The larger value of the two intervals specified in the commands is used as the suppression period.

5. Run commit

   The configuration is committed.

Setting the Interval at Which LSAs Are Received

You can set the interval at which LSAs are received based on network connections and router resources.

Context

In OSPF, the defined interval at which LSAs are received is 1s. This aims to prevent network connections or frequent route flapping from consuming excessive network bandwidth or device resources.

On a stable network that requires fast route convergence, you can cancel the interval at which LSAs are received by setting the interval to 0s. After the interval is set to 0s, topology or route changes can be immediately advertised on the network through LSAs, which speeds up route convergence.

Procedure

1. Run system-view

   The system view is displayed.

2. Run ospf [ process-id ]

   The OSPF process view is displayed.

3. Run lsa-arrival-interval { interval | intelligent-timer max-interval start-interval hold-interval }

   The interval at which LSAs are received is set.

   • The parameter interval sets the interval at which LSAs are received, in milliseconds.
   • The parameter intelligent-timer sets the interval at which router LSAs or network LSAs are received using an intelligent timer.
   • The parameter max-interval sets the maximum interval at which LSAs are received, in milliseconds.
   • The parameter start-interval sets the initial interval at which LSAs are received, in milliseconds.
   • The parameter hold-interval sets the hold interval at which LSAs are received, in milliseconds.

   By default, intelligent timer is enabled, and the default maximum interval at which LSAs are received is 1000 ms, the default initial interval is 500 ms, and the default hold interval is 500 ms. Details about the interval at which LSAs are received are as follows:

   1. start-interval specifies the initial interval at which LSAs are received.
   2. The interval at which LSAs are received for the nth (n ≥ 2) time = hold-interval x 2 x (n-1).
   3. When the interval specified in hold-interval x 2 x (n-1) reaches the maximum interval specified in max-interval, OSPF receives LSAs at the maximum interval for three consecutive times. Then, OSPF goes back to Step 3.a and receives LSAs at the initial interval specified in start-interval.

4. (Optional) Run lsa-arrival-interval suppress-flapping suppress-interval [ threshold threshold ]

   The suppression period that takes effect when received OSPF LSAs flap is configured.

   If no flapping occurs among received OSPF LSAs, the configuration of the lsa-arrival-interval command prevents the device from frequently receiving LSAs. If received OSPF LSAs flap, the configuration of the lsa-arrival-interval suppress-flapping command minimizes the impact of the flapping on services. The larger value of the two intervals specified in the commands is used as the suppression period.

5. Run commit

   The configuration is committed.

Setting the Interval for the SPF Calculation

By setting the interval for the SPF calculation, you can save resources consumed by frequent network changes.

Context

When the OSPF LSDB changes, the shortest path needs to be recalculated. If a network changes frequently, the shortest path is calculated accordingly, which consumes a large number of system resources degrades system performance. By configuring an intelligent timer and a proper interval for the SPF calculation, you can prevent excessive system memory and bandwidth resources from being occupied.

Procedure

1. Run system-view

   The system view is displayed.

2. Run ospf [ process-id ]

   The OSPF process view is displayed.

3. Run spf-schedule-interval { interval1 | intelligent-timer max-interval start-interval hold-interval [ conservative ] | millisecond interval2 }

   The interval for the SPF calculation is set.

   The interval for the SPF calculation is as follows:

   1. The initial interval for the SPF calculation is specified in start-interval.
   2. The interval for the SPF calculation for the nth (n≥2) time is equal to hold-interval × 2(n-2).
   3. When the interval specified in hold-interval × 2(n-2) reaches the maximum interval specified in max-interval, OSPF performs the SPF calculation at the maximum interval until no SPF calculation is performed within max-interval. After the maximum interval elapses, the calculation mechanism goes back to step 1.

   4. If no flapping occurs within the interval of max-interval that starts upon the end of the previous SPF calculation, the intelligent timer exits.

   5. If no flapping occurs in the previous interval and flapping occurs in the current interval, SPF calculation is delayed for a period of the start-interval. After the SPF calculation is complete, the current interval is used for the next SPF calculation.

4. Run commit

   The configuration is committed.

Configuring the Function to Suppress the Advertisement of Interface Addresses

This section describes how to configure the function to suppress the advertisement of interface addresses so that interface addresses can be reused.

Procedure

• Configuring the function to suppress the advertisement of all interface addresses in an OSPF process
  1. Run system-view

     The system view is displayed.

  2. Run ospf [ process-id ]

     The OSPF process view is displayed.

  3. Run suppress-reachability

     The suppresses the advertisement of all interface addresses in an OSPF process is configured.

  4. Run commit

     The configuration is committed.

• Configuring an OSPF interface to suppress the advertisement of interface addresses
  1. Run system-view

     The system view is displayed.

  2. Run interface interface-type interface-number

     The OSPF interface view is displayed.

  3. Run ospf suppress-reachability

     An OSPF interface to suppress the advertisement of interface addresses is configured.

  4. Run commit

     The configuration is committed.

Configuring the Route Calculation Delay Function to Suppress Frequent LSA Flapping

A route calculation delay can suppress frequent OSPF LSA flapping.

Context

Frequent OSPF LSA flapping on the remote device may lead to route flapping on the local device, affecting services. To address this problem, run the maxage-lsa route-calculate-delay command to configure the local device to delay route calculation in the case of frequent OSPF LSA flapping, which suppresses route flapping locally.

Procedure

1. Run system-view

   The system view is displayed.

2. Run ospf [ process-id ]

   The OSPF process view is displayed.

3. Run maxage-lsa route-calculate-delay delay-interval

   The route calculation delay function is configured to suppress frequent OSPF LSA flapping.

4. Run commit

   The configuration is committed.

Disabling Master/Slave Board Switching Triggered by Abnormal OSPF LSA Aging

By default, master/slave board switching triggered by abnormal OSPF LSA aging is enabled. To disable this function, perform this task.

Context

When the local device's aging timer expires, the local device incorrectly clears all Router LSAs from the peer device, which causes route flapping and service interruptions. To resolve this issue, master/slave board switching triggered by abnormal OSPF LSA aging is automatically enabled. Master/slave board switching is triggered to restore network connections and service traffic when the following condition is met:

(Number of incorrectly cleared Router LSAs/Total number of Router LSAs) x 100% ≥ 80% (Router LSAs are those sent by the peer device to the local device)

Procedure

1. Run system-view

   The system view is displayed.

2. Run ospf maxage-lsa auto-protect disable

   The master/slave board switching triggered by abnormal OSPF LSA aging is disabled.

3. Run commit

   The configuration is committed.

Disabling OSPF LSA Aging Management

By default, the OSPF LSA aging management function is enabled. To disable this function, perform this task.

Context

If an exception occurs in the age field of LSAs, LSAs may be aged unexpectedly, causing LSA flapping or a route calculation error. For example, if the abnormal aging time is 2500s and the actual aging time is 500s, LSAs are aged prematurely. To address this problem, OSPF LSA aging management is enabled by default. If the aging time in a received LSA is greater than 1800s, OSPF considers the LSA abnormal and changes the aging time to 1700s until the aging time values of all LSAs in the area become the same. In this case, routes can be calculated correctly.

By default, the OSPF LSA aging management function is enabled. To disable this function, run the lsa-age refresh disable command.

Procedure

1. Run system-view

   The system view is displayed.

2. Run lsa-age refresh disable

   OSPF LSA aging management is disabled.

3. Run commit

   The configuration is committed.

Setting a Period During Which OSPF Keeps the Maximum Cost in Local LSAs

If a period during which OSPF keeps the maximum cost in local LSAs is configured and an OSPF interface changes from Down to Up, traffic is switched back only when the period elapses.

Context

When an OSPF interface changes from Down to Up, the OSPF neighbor relationship is re-established. When IGP route convergence ends, traffic is switched back. IGP routes converge fast. Many services that depend on IGP routes may require a delayed switchback. In this case, you can run the ospf peer hold-max-cost command so that OSPF keeps the maximum cost in local LSAs for a specified period after the OSPF neighbor relationship reaches Full state. During this period, the traffic forwarding path remains unchanged. After this period elapses, the original cost is restored, and traffic is switched back.

Procedure

1. Run system-view

   The system view is displayed.

2. Run interface interface-type interface-number

   The interface view is displayed.

3. Run ospf peer hold-max-cost timer timer

   A period during which OSPF keeps the maximum cost in local LSAs is set.

4. Run commit

   The configuration is committed.

Configuring Secure Synchronization

Secure synchronization prevents traffic loss after a device is restarted.

Context

When the NEs in an area just finish synchronizing the LSDBs, the LSDBs of these NEs are different from each other. As a result, route flapping occurs. You can configure secure synchronization to solve this problem. This, however, may delay the establishment of the OSPF neighbor relationship.

Procedure

1. Run system-view

   The system view is displayed.

2. Run ospf [process-id ]

   The OSPF view is displayed.

3. Run safe-sync enable

   Secure synchronization is configured.

4. Run commit

   The configuration is committed.

Verifying the Configuration of the OSPF Network Convergence Speed

After configuring OSPF fast network convergence, verify OSPF brief information.

Prerequisites

OSPF fast convergence has been configured.

Procedure

• Run the display ospf [ process-id ] brief command to check brief information about the specified OSPF process.
• Run the display ospf [ process-id ] statistics maxage-lsa command to check information about router LSAs that have reached the aging time.

Example

Run the display ospf brief command to view information about OSPF timers.

<HUAWEI> 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
OSPF is in LSDB overflow status(remain time: 205s)
Retransmission limitation is disabled
Import routes limitation is enabled
  Self ASE LSA count: 8
  Current status: Normal
bfd enabled
BFD Timers: Tx-Interval 10 , Rx-Interval 10 , Multiplier 3 
Area Count: 2   Nssa Area Count: 1 
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 (GE0/3/0)
 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

 Area: 0.0.0.1             (MPLS TE not enabled)
 Authtype: None   Area flag: NSSA
 SPF scheduled count: 1
 Exchange/Loading neighbors: 0
 NSSA Translator State: Elected
 Router ID conflict state: Normal
 Import routes limitation is enabled
  Self NSSA LSA count: 2
  Current status: Normal

 Interface: 1.1.1.1 (GE0/2/0)
 Cost: 1       State: P-2-P   Type: P2P      MTU: 1500
 Timers: Hello 10, Dead 40, Wait 40, Poll 120, Retransmit 5, Transmit Delay 1
 Multi-area interface

Run the display ospf [ process-id ] statistics maxage-lsa command to view information about router LSAs that have reached the aging time.

<HUAWEI> display ospf statistics maxage-lsa
          OSPF Process 1 with Router ID 1.1.1.1
               Statistics of Router-LSAs

         -------------------------------------------

                     Area: 0.0.0.0
LinkState ID                 MaxAge count       Last MaxAge time
     1.1.1.1                            1   2014-03-22  11:12:00

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