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ME60 V800R010C10SPC500 Configuration Guide - IP Routing 01

This is ME60 V800R010C10SPC500 Configuration Guide - IP Routing
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Adjusting the IPv4 IS-IS Route Convergence Speed

Adjusting the IPv4 IS-IS Route Convergence Speed

Accelerating IS-IS route convergence can improve the fault location efficiency and network reliability.

Usage Scenario

The procedure for implementing IS-IS is as follows:
  • Establishment of neighbor relationships: establishes neighbor relationships by exchanging Hello packets between two devices.

  • LSP flooding: implements LSDB synchronization between devices in the same area.

  • SPF calculation: uses the SPF algorithm to calculate IS-IS routes, and delivers IS-IS routes to the routing table.

To accelerate the IS-IS route convergence, configure the following parameters:
  • Interval for detecting failures on IS-IS neighboring devices

  • Flooding parameters of CSNPs and LSPs

  • Interval for SPF calculation

You can also configure convergence priorities for IPv4 IS-IS routes so that key routes can converge first if the network topology changes, which minimizes adverse impacts on key services.

Pre-configuration Tasks

Before adjusting the IPv4 IS-IS route convergence speed, complete the following tasks:

  • Configure the link layer protocol on interfaces.

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

  • Configure basic IPv4 IS-IS functions.

Configuration Procedures

Perform one or more of the following configurations as required.

Configuring the Interval for Detecting IS-IS Neighboring Device Failures

To minimize the impacts of neighboring device failures on IS-IS networks, accelerate the detection IS-IS neighboring device failures.

Context

Connection status between an IS-IS device and its neighboring devices can be monitored by exchanging Hello packets at intervals. An IS-IS neighboring device is considered Down if the IS-IS device does not receive any Hello packets from the neighboring device within a specified period (holding time). A failure in an IS-IS neighboring device will trigger LSP flooding and SPF calculation, after which IS-IS routes re-converge.

To adjust the fault detection speed, use the following methods to accelerate the detection IS-IS neighboring device failures:
  • Configure the interval at which Hello packets are sent.

  • Configure the number of Hello packets that are sent before the local device considers the neighbor Down.

    NOTE:

    Holding time of neighboring devices = Interval at which Hello packets are sent x Number of Hello packets that are sent before the local device considers the neighbor Down. The maximum value of the holding time is 65535s.

  • Configure Dynamic BFD for IS-IS.

    NOTE:

    Configuring IPv4 BFD for IS-IS is recommended because this method ensures faster fault detection than the other two methods.

Procedure

  • Set an interval at which Hello packets are sent.
    1. Run system-view

      The system view is displayed.

    2. Run interface interface-type interface-number

      The interface view is displayed.

    3. Run isis timer hello hello-interval [ level-1 | level-2 ] [ conservative ]

      The interval at which Hello packets are sent is set.

      If the conservative parameter is specified in the command, the conservative mode is enabled for the holdtime of the IS-IS neighbor relationship.
      • If the parameter is specified and the holdtime of the IS-IS neighbor relationship is less than 20s, the IS-IS neighbor relationship is disconnected when the hold time elapses.
      • If the parameter is not specified and the holdtime of the IS-IS neighbor relationship is less than 20s, the IS-IS neighbor relationship is disconnected when the period of the hold time and a delay elapses.

      NOTE:

      A broadcast link can transmit both Level-1 and Level-2 Hello packets. You can set different intervals for these two types of Hello packets. By default, both Level-1 and Level-2 Hello packets are sent.

      A P2P link can transmit only one type of Hello packets. Therefore, neither level-1 or level-2 needs to be specified if a P2P link is used.

      The timer 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.

  • Set the number of Hello packets that are sent before the local device considers the neighbor Down.
    1. Run system-view

      The system view is displayed.

    2. Run interface interface-type interface-number

      The interface view is displayed.

    3. Run isis timer holding-multiplier number [ level-1 | level-2 ]

      The number of Hello packets that are sent before the local device considers the neighbor Down is configured.

      NOTE:

      A broadcast link can transmit both Level-1 and Level-2 Hello packets. You can set different intervals for these two types of Hello packets. By default, both Level-1 and Level-2 Hello packets are sent.

      A P2P link can transmit only one type of Hello packets. Therefore, neither level-1 or level-2 needs to be specified if a P2P link is used.

    4. Run commit

      The configuration is committed.

Setting Flooding Parameters of SNPs and LSPs

To speed up LSDB synchronization between devices, set proper values for flooding parameters of SNPs and LSPs.

Context

SNPs consist of CSNPs and PSNPs. CSNPs carry summaries of all LSPs in LSDBs, ensuring LSDB synchronization between neighboring routers. SNPs are processed differently on broadcast links and P2P links.
  • On a broadcast link, CSNPs are periodically sent by a DIS device. If a router detects that its LSDB is not synchronized with that on its neighboring router, the router will send PSNPs to apply for missing LSPs.

  • On a P2P link, CSNPs are sent only during initial establishment of neighbor relationships. If a request is acknowledged, a neighboring router will send a PSNP in response to a CSNP. If a router detects that its LSDB is not synchronized with that on its neighboring router, the router will send PSNPs to apply for missing LSPs.

Procedure

  • Set an interval at which CSNPs are sent.
    1. Run system-view

      The system view is displayed.

    2. Run interface interface-type interface-number

      The interface view is displayed.

    3. Run isis timer csnp csnp-interval [ level-1 | level-2 ]

      The interval at which CSNPs are sent is set on the specified interface.

      NOTE:

      Configure Level-1 and Level-2 only when a broadcast interface is specified.

    4. Run commit

      The configuration is committed.

  • Configure the intelligent timer to control LSP generation.
    1. Run system-view

      The system view is displayed.

    2. Run isis [ process-id ]

      The IS-IS view is displayed.

    3. Run timer lsp-generation max-interval [ init-interval [ incr-interval ] ] [ level-1 | level-2 ]

      The intelligent timer is configured to control LSP generation.

      Before using the timer lsp-generation command, note the following:
      • When only max-interval is specified, the intelligent timer functions as an ordinary one-time triggering timer.

      • If init-interval and incr-interval are specified, init-interval is used as the LSP generation interval for the first time, and incr-interval is used as the LSP generation interval for the second time. From the third time on, the LSP generation interval doubles each time until the interval reaches max-interval. If the local routing information keeps being updated within the max-interval period, the interval remains at max-interval until the time the local routing information is not updated within the max-interval period or the IS-IS process is restarted. Then the interval decreases to init-interval.

      • If init-interval is specified, but incr-interval is not, init-interval is used as the LSP generation interval for the first time, and then max-interval is used as the interval. If the local routing information keeps being updated within the max-interval period, the interval remains at max-interval until the time the local routing information is not updated within the max-interval period or the IS-IS process is restarted. Then the interval decreases to init-interval.

    4. Run suppress-flapping lsp-generation timer delay-interval [ threshold threshold-value ]

      A period is specified for the system to delay generating the same LSP during route flapping.

    5. Run commit

      The configuration is committed.

  • Set the size of an LSP.
    1. Run system-view

      The system view is displayed.

    2. Run isis [ process-id ]

      The IS-IS view is displayed.

    3. Run lsp-length originate max-size

      The size of an LSP to be generated is set.

    4. Run lsp-length receive max-size

      The size of an LSP to be received is set.

      NOTE:

      max-size of an LSP to be generated must be less than or equal to max-size of an LSP to be received.

      The value of max-size in the lsp-length command must meet the following conditions.
      • The MTU of an Ethernet interface must be greater than or equal to the sum of the value of max-size plus 3.

      • The MTU of a P2P interface must be greater than or equal to the value of max-size.

    5. Run commit

      The configuration is committed.

  • Set the LSP update interval.
    1. Run system-view

      The system view is displayed.

    2. Run isis [ process-id ]

      The IS-IS view is displayed.

    3. Run timer lsp-refresh refresh-time

      An LSP update interval is set.

      To synchronize all LSPs in the areas, IS-IS regularly transmits all the current LSPs to neighbors.

      Ensure that the LSP update interval is at least 300s shorter than the maximum LSP lifetime so that new LSPs can reach all devices in an area before existing LSPs expire.

      NOTE:

      The larger a network, the greater the deviation between the LSP update interval and the maximum LSP lifetime.

    4. Run commit

      The configuration is committed.

  • Set the maximum lifetime for LSPs.
    1. Run system-view

      The system view is displayed.

    2. Run isis [ process-id ]

      The IS-IS view is displayed.

    3. Run timer lsp-max-age age-time

      The maximum lifetime is set for LSPs.

      When a device generates the system LSP, it fills in the maximum lifetime for this LSP. The lifetime of the LSP decreases with time. If the device does not receive any update LSPs and the lifetime of the LSP is reduced to 0, the device keeps the LSP for another 60s. If the device fails to receive any update LSPs within the 60s, it deletes the LSP from the LSDB.

    4. Run commit

      The configuration is committed.

  • Set the maximum holdtime for the largest IS-IS route cost in local LSPs.
    1. Run system-view

      The system view is displayed.

    2. Run interface interface-type interface-number

      The interface view is displayed.

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

      The maximum holdtime for the largest IS-IS route cost in local LSPs is set.

      When a Down IS-IS interface goes Up, IS-IS neighbor relationships are re-established on the interface, and traffic is switched back to this Up interface after IGP route convergence. IGP route convergence is fast, but many services that depend on IGP routes may not expect such fast traffic switchback. To delay traffic switchback after IGP route convergence, run the isis peer hold-max-cost command to set the maximum holdtime for the largest IS-IS route cost (16777214 in wide mode and 63 in narrow mode) in local LSPs. In this manner, before the specified maximum holdtime expires, traffic is not switched back to this route due to its large cost. After the specified maximum holdtime expires, the route cost reverts to the original value, and then traffic is switched back to this route.

    4. Run commit

      The configuration is committed.

  • Set the minimum interval at which LSPs are sent.
    1. Run system-view

      The system view is displayed.

    2. Run interface interface-type interface-number

      The interface view is displayed.

    3. Run isis timer lsp-throttle throttle-interval [ count count ]

      The minimum interval at which LSPs are sent is set.

      The count parameter specifies the maximum number of LSPs that can be sent within the interval specified by throttle-interval. The value of count is an integer ranging from 1 to 1000.

    4. Run commit

      The configuration is committed.

  • Enable LSP fast flooding.
    1. Run system-view

      The system view is displayed.

    2. Run isis [ process-id ]

      The IS-IS view is displayed.

    3. Run flash-flood [ lsp-count | max-timer-interval interval | [ level-1 | level-2 ] ] *

      The LSP fast flooding is enabled.

      The flash-flood command speeds up LSP flooding by flooding newly generated or received LSPs immediately without waiting for the expiry of the timer set using the isis timer lsp-throttle command.

      You can specify lsp-count to flood a certain number of LSPs and specify interval to flood LSPs at a certain interval. If the number of LSPs to be flooded exceeds the value of lsp-count, a maximum of lsp-count number of LSPs are flooded each time in time sequence at an interval specified by interval until all the LSPs are flooded.

      When LSP fast flooding is enabled, Level-1 LSPs and Level-2 LSPs are fast flooded by default if no level is specified.

    4. Run suppress-flapping lsp-flood timer delay-interval [ threshold threshold-value ]

      A period is specified for the system to delay LSP flooding during route flapping.

    5. Run commit

      The configuration is committed.

  • Set an interval at which LSPs are retransmitted over a P2P link.
    1. Run system-view

      The system view is displayed.

    2. Run interface interface-type interface-number

      The interface view is displayed.

    3. (Optional) Run isis circuit-type p2p [ strict-snpa-check ]

      The broadcast interface is simulated as a P2P interface.

      An interval at which LSPs are retransmitted takes effect only on P2P interfaces. Therefore, to configure the interval on a broadcast interface, change the broadcast interface to a P2P interface first.

    4. Run isis timer lsp-retransmit retransmit-interval

      The interval at which LSPs are retransmitted over a P2P link is set.

    5. Run commit

      The configuration is committed.

  • Configure automatic IS-IS LSP Remaining Lifetime adjustment.
    1. Run system-view

      The system view is displayed.

    2. (Optional) Run undo lsp-remaining-lifetime refresh disable

      Automatic IS-IS LSP Remaining Lifetime adjustment is enabled.

      By default, automatic IS-IS LSP Remaining Lifetime adjustment is enabled.

    3. Run lsp-remaining-lifetime refresh timer { refreshvalue | lsp-max-age }

      An IS-IS LSP Remaining Lifetime value is set.

    4. Run commit

      The configuration is committed.

Setting the SPF Calculation Interval

To improve the fault location efficiency on an IS-IS network and prevent SPT calculation from consuming excessive system resources, set the SPF calculation interval to a proper value.

Context

A network change can trigger IS-IS to perform SPT calculation. Frequent SPT calculation will consume excessive CPU resources, affecting services.

To solve this problem, configure an intelligent timer to control the SPT calculation interval. For example, to speed up IS-IS route convergence, set the interval for SPT calculation to a small value, and set the interval to a large value after the IS-IS network becomes stable.

Procedure

  1. Run system-view

    The system view is displayed.

  2. Run isis [ process-id ]

    The IS-IS view is displayed.

  3. Run timer spf max-interval [ init-interval [ incr-interval ] ]

    The SPT intelligent timer is configured.

    The delay for SPF calculation is described as follows:
    • The delay for the first SPF calculation is init-interval; the delay for the second SPF calculation is incr-interval. From the third time on, the delay for SPF calculation doubles each time until the delay reaches max-interval.If network flapping persists within the max-interval period, max-interval is used as the delay for SPF calculation. If network flapping does not occur within the max-interval period or if the IS-IS process is restarted, init-interval is used as the delay for SPF calculation.
    • If incr-interval is not specified, the delay for SPF calculation for the first time is init-interval. From the second time on, the delay is max-interval. If the local routing information keeps being updated within the max-interval period, the delay remains at max-interval until the time the local routing information is not updated within the max-interval period or the IS-IS process is restarted. Then the delay decreases to init-interval.
    • When only max-interval is specified, the intelligent timer functions as an ordinary one-time triggering timer.

  4. Run suppress-flapping route-calculate timer delay-interval [ threshold threshold-value ]

    A period is specified for the device to delay route calculation when the device receives a purge LSP.

  5. Run timer purge-zero-lsp route-calculate-delay delay-interval

    A period is specified for the device to delay route calculation when the device receives a purge LSP.

  6. Run commit

    The configuration is committed.

Configuring Convergence Priorities for IPv4 IS-IS Routes

IS-IS routes with higher convergence priority converge preferentially when the network topology changes, which minimizes the impacts on critical services. This section describes how to configure convergence priorities for IS-IS routes.

Context

The ME60 allows you to configure the highest convergence priority for specific IS-IS routes so that those IS-IS routes converge first when a network topology changes.

Procedure

  1. Run system-view

    The system view is displayed.

  2. Run isis [ process-id ]

    The IS-IS view is displayed.

  3. Run prefix-priority [ level-1 | level-2 ] { critical | high | medium } { ip-prefix prefix-name | tag tag-value }

    A convergence priority is set for IS-IS routes.

    The convergence priorities for IS-IS routes are used as follows:
    • Existing IS-IS routes converge based on the priorities configured in the prefix-priority command.

    • New IS-IS routes that match the filtering rules converge based on the priorities configured in the prefix-priority command.

    • If an IS-IS route meets the matching rules of multiple convergence priorities, the highest convergence priority is used.

    • The convergence priority of Level-1 IS-IS routes is higher than that of Level-2 IS-IS routes.

    • If the route level is not specified, the configuration of the prefix-priority command takes effect on both Level-1 and Level-2 IS-IS routes.

    NOTE:

    The prefix-priority command is only applicable to the public network.

    After the prefix-priority command is run, the convergence priority of 32-bit host routes is low, and the convergence priorities of the other routes are specified in the prefix-priority command.

  4. Run commit

    The configuration is committed.

Verifying the IPv4 IS-IS Route Convergence Speed Configuration

After configuring parameters to adjust the IPv4 IS-IS route convergence speed, check the configurations.

Procedure

  • Run the display isis interface [ [ verbose | traffic-eng ] * | tunnel ] [ process-id | vpn-instance vpn-instance-name ] command to check IS-IS packet information.
  • Run the display isis route [ process-id | vpn-instance vpn-instance-name ] [ ipv4 ] [ topology topology-name ] [ verbose | [ level-1 | level-2 ] | ip-address [ mask | mask-length ] ] * command to check the priority of IS-IS routes.

Example

Run the display isis interface verbose command. The command output shows that GE 1/0/0 sends Hello packets at an interval of 15s, the holding multiplier of neighboring devices is 10, Level-1 CSNPs are sent at an interval of 123s, and the minimum interval at which LSPs are sent is 159s.

<HUAWEI> display isis interface verbose
 GE1/0/0         001     Up                  Down            1497 L1/L2 No/No
  Description                 : HUAWEI, Quidway Series, GigabitEthernet1/0/0 Interface
  SNPA Address                : 00e0-095b-4201
  IP Address                  : 123.1.1.1
  IPV6 Link Local Address     :
  IPV6 Global Address(es)     :
  Csnp Timer Value            :  L1   123  L2    10
  Hello Timer Value           :  L1    15  L2    15
  Hello Multiplier Value      :  L1    10  L2    10
  LSP-Throttle Timer          :  L12  159
  Cost                        :  L1    10  L2    10
  Ipv6 Cost                   :  L1    10  L2    10
  Priority                    :  L1    64  L2    64
  Retransmit Timer Value      :  L12    5
  Bandwidth-Value             :  Low 100000000  High         0
  Fast-Sense Rpr              :  NO

Run the display isis route verbose command. The command output shows that the convergence priority of the route 10.10.10.0/24 imported by IS-IS is Critical.

<HUAWEI> display isis route verbose

                         Route information for ISIS(1)
                         -----------------------------

                        ISIS(1) Level-2 Forwarding Table
                        --------------------------------

 IPV4 Dest  : 10.10.10.0/24      Int. Cost : 20              Ext. Cost : NULL
 Admin Tag  : -                  Src Count : 2               Flags     : A/-/-/-
 Priority   : Critical
 NextHop    :                    Interface :                 ExitIndex :
    1.1.1.2                            GigabitEthernet1/0/0                     0x80000001
                                                      
 IPV4 Dest  : 1.1.1.0/24         Int. Cost : 10              Ext. Cost : NULL
 Admin Tag  : -                  Src Count : 2               Flags     : D/-/L/-
 Priority   : Medium
 NextHop    :                    Interface :                 ExitIndex :
    Direct                             GigabitEthernet1/0/0                     0x00000000

 IPV4 Dest  : 20.20.20.0/24      Int. Cost : 20              Ext. Cost : NULL
 Admin Tag  : -                  Src Count : 2               Flags     : A/-/-/-
 Priority   : Low
 NextHop    :                    Interface :                 ExitIndex :
    1.1.1.2                            GigabitEthernet1/0/0                     0x80000001

     Flags: D-Direct, A-Added to URT, L-Advertised in LSPs, S-IGP Shortcut
                               U-Up/Down Bit Set
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Updated: 2019-01-04

Document ID: EDOC1100059437

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