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ME60 V800R010C10SPC500 Configuration Guide - IP Routing 01

This is ME60 V800R010C10SPC500 Configuration Guide - IP Routing
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Huawei uses machine translation combined with human proofreading to translate this document to different languages in order to help you better understand the content of this document. Note: Even the most advanced machine translation cannot match the quality of professional translators. Huawei shall not bear any responsibility for translation accuracy and it is recommended that you refer to the English document (a link for which has been provided).
Adjusting OSPF Route Selection

Adjusting OSPF Route Selection

By adjusting OSPF route selection, you can enable OSPF to meet the requirements of complex networks.

Usage Scenario

In real world situations, you can configure an OSPF route selection rule by setting OSPF route attributes to meet the requirements of complex networks.

  • Set the cost of an interface. The link connected to the interface with a smaller cost value preferentially transmits routing information.
  • Configure equal-cost routes to implement load balancing.
  • Configure a stub router during the maintenance operations such as upgrade to ensure stable data transmission through key routes.
  • Suppress interfaces from sending or receiving packets to help select the optimal route.
  • Configuring an OSPF interface to automatically adjust the link cost based on link quality that facilitates route selection control and improves network reliability.

Pre-configuration Tasks

Before adjusting OSPF route selection, complete the following tasks:

Configuration Procedures

Perform one or more of the following configurations as required.

Setting the Interface Cost

You can adjust and optimize route selection by setting the OSPF interface cost.

Context

After the OSPF interface costs are set, the interface with a smaller cost value preferentially transmits routing information. This helps select the optimal route.

The OSPF interface cost can be set or calculated based on the interface bandwidth.

Procedure

  • Manually configure a cost for an OSPF interface.
    1. Run system-view

      The system view is displayed.

    2. Run interface interface-type interface-number

      The interface view is displayed.

    3. Run ospf cost cost

      A cost is set for the interface.

    4. Run commit

      The configuration is committed.

  • Configure bandwidth-based automatic OSPF interface cost calculation.

    The calculation formula is as follows: Interface cost = Bandwidth reference value/Interface bandwidth. The integer of the calculation result is used as the cost of the interface. If the result is less than 1, the cost is 1.

    1. Run system-view

      The system view is displayed.

    2. Run ospf [ process-id ]

      The OSPF view is displayed.

    3. Run bandwidth-reference value

      A bandwidth reference value is set.

    4. Run commit

      The configuration is committed.

Configuring Equal-Cost Routes

You can set the number of OSPF equal-cost routes and route preference to implement load balancing and adjust route selection.

Context

If the destinations and costs of the multiple routes discovered by one routing protocol are the same, load balancing can be implemented among the routes.

As shown in Figure 5-2, three routes between Device A and Device B that run OSPF have the same costs. The three routes are equal-cost routes for load balancing.

Figure 5-2 Networking diagram of equal-cost routes

Procedure

  1. Run system-view

    The system view is displayed.

  2. Run ospf [ process-id ]

    The OSPF process view is displayed.

  3. Run maximum load-balancing number

    The maximum number of equal-cost routes is set.

    If the number of equal-cost routes is greater than number specified in the maximum load-balancing command, routes are selected for load balancing based on the following criteria:

    1. Route priority: Routes with smaller priority values are selected for load balancing. For details about route priority configuration, see 4.
    2. Interface index: If routes have the same priority, those with greater interface index values are selected for load balancing.
    3. Next hop IP address: If routes have the same priority and interface index, those with larger IP addresses are selected for load balancing.

  4. (Optional) Run either of the following commands:

    • To configure a priority for an equal-cost route, run the nexthop ip-address weight value command.

      Among equal-cost OSPF routes, those with smaller priority values configured using the nexthop command are selected for load balancing.

      • ip-address specifies the next hop address of the equal-cost route.
      • value specifies the weight of the next hop.
    • To configure priorities for the routes with a TE tunnel interface or an IPv4 interface as the outbound interface for route selection if both an IGP-Shortcut-enabled TE tunnel and IP link are available, run the ecmp prefer { te-tunnel | intact } command.

  5. Run commit

    The configuration is committed.

Setting the convergence priority for OSPF routes

You can adjust and optimize route selection by setting the convergence priority for OSPF routes.

Context

To set the convergence priority of OSPF routes based on a specified IP prefix list takes effect on the public network only.

OSPF route calculation, link-state advertisement (LSA) flooding, and LSDB synchronization can be implemented according to the configured priority. Therefore, route convergence can be controlled.

When an LSA meets multiple priorities, the highest priority takes effect.

OSPF calculates LSAs in the sequence of intra-area routes, inter-area routes, and AS external routes. This command enables OSPF to calculate the three types of routes separately according to the specified route calculation priorities. Convergence priorities are critical, high, medium, and low. To speed up the processing of LSAs with the higher priority, during LSA flooding, the LSAs need to be placed into the corresponding critical, high, medium, and low queues according to priorities.

Procedure

  1. Run system-view

    The system view is displayed.

  2. Run ip_ip-prefix ip-prefix-name [ index index-number ] { permit | deny } ipv4-address mask-length [ match-network ] [ greater-equal greater-equal-value ] [ less-equal less-equal-value ]

    The IP prefix list is configured.

  3. Run ospf [ process-id ]

    The OSPF process is started and OSPF view is displayed.

  4. Run prefix-priority { critical | high | medium } ip-prefix ip-prefix-name

    The convergence priority for OSPF routes is set.

  5. Run commit

    The configuration is committed.

Configuring a Stub Router

To ensure that a route is not interrupted during flapping-triggering maintenance operations such as upgrade, you can configure a ME device as a stub router to allow traffic to bypass the route on the stub router.

Context

After a stub router is configured, the route on the stub router will not be preferentially selected. After the route cost is set to the maximum value 65535, traffic generally bypasses the ME device. This ensures an uninterrupted route on the ME device during maintenance operations such as upgrade.

Procedure

  1. Run system-view

    The system view is displayed.

  2. Run ospf [ process-id ]

    The OSPF process view is displayed.

  3. Run stub-router [ on-startup [ interval ] | include-stub | external-lsa [ externallsa-metric ] | summary-lsa [ summarylsa-metric ] ] *

    A stub router is configured.

    NOTE:

    The stub router configured in this manner is irrelevant to the ME device in the stub area.

  4. (Optional) Run maximum-link-cost cost

    The maximum cost is set for OSPF links.

  5. Run commit

    The configuration is committed.

Suppressing an Interface from Receiving and Sending OSPF Packets

After an interface is suppressed from receiving and sending OSPF packets, routing information can bypass a specific ME device and the local ME device can reject routing information advertised by another ME device.

Context

Suppressing an interface from receiving and sending OSPF packets helps routing information to bypass a specific ME device and enables the local ME device to reject routing information advertised by another ME device. This ensures that an optimal route is provided.

For example, there are three routes between Device A and Device B, as shown in Figure 5-3. To configure the route with the outbound interface of Interface 2 to be the optimal route, suppress Interface 1 and Interface 3 from receiving and sending OSPF packets.

Figure 5-3 Networking diagram of suppressing an interface from receiving and sending OSPF packets

Procedure

  1. Run system-view

    The system view is displayed.

  2. Run ospf [ process-id ]

    The OSPF process view is displayed.

  3. Run silent-interface { all | interface-type interface-number }

    An interface is suppressed from receiving and sending OSPF packets.

    The same interface in different processes can be suppressed from sending and receiving OSPF packets, but the silent-interface command is valid only for the OSPF interface in the local process.

    After an OSPF interface is configured to be in the silent state, the interface can still advertise its direct routes. Hello packets on the interface, however, cannot be forwarded. Therefore, no neighbor relationship can be established on the interface. This can enhance the networking adaptability of OSPF and reduce system resource consumption.

  4. Run commit

    The configuration is committed.

Configuring an OSPF Interface to Automatically Adjust the Link Cost

Configuring an OSPF interface to automatically adjust the link cost based on link quality facilitates route selection control and improves network reliability.

Context

A bit error refers to the deviation between a bit that is sent and the bit that is received. The bit error rate (BER) refers to the number of bit errors divided by the total number of bits transferred during a studied time interval. During data transmission, a high BER will degrade or even interrupt services in extreme cases.

To prevent this problem, configure OSPF interfaces to automatically adjust link costs based on link quality so that unreliable links are not used by the optimal routes.

Procedure

  1. Run system-view

    The system view is displayed.

  2. Run interface interface-type interface-number

    The interface view is displayed.

  3. (Optional) Run bit-error-mode { crc | prefec [ trigger-interval time-interval ] }

    Bit error detection is enabled on the interface.

    NOTE:
    Bit error detection is classified as CRC bit error detection or Prefec bit error detection.

  4. Run link-quality low bit-error-threshold error-ratio trigger-coefficient trigger-power resume-ratio recovery-coefficient recovery-power

    Bit error detection is enabled on the interface, and a BER threshold is set.

  5. Run ospf enable [ process-id ] area area-id

    OSPF is enabled on the interface.

  6. Run ospf link-quality low incr-cost { cost | max-reachable }

    The OSPF interface is configured to automatically adjust the link cost based on link quality.

    NOTE:

    The cost parameter specifies the link cost adjustment value. After this parameter is specified:

    • If the link quality changes from good to low, the link cost equals the original link cost plus the adjustment value. The maximum link cost allowed is 65535.
    • If the link quality changes from low to good, the original link cost applies.

  7. Run commit

    The configuration is committed.

Configuring a Fallback Cost for an Eth-Trunk Interface

A fallback cost of an Eth-Trunk interface helps adjust route selection dynamically.

Context

If a member interface of an Eth-Trunk interface goes down, the remaining bandwidth of the Eth-Trunk interface may fail to meet user requirements. As a result, user services are affected. To address this problem, run the ospf cost-fallback command to configure cost-fallback parameters (fallback cost and bandwidth threshold) for the Eth-Trunk interface; if the remaining bandwidth of the Eth-Trunk interface goes below the bandwidth threshold, the cost of the interface is changed to the fallback cost which is higher than the normal cost, and traffic is then switched to an alternative path; when the remaining bandwidth of the Eth-Trunk interface reaches or exceeds the bandwidth threshold, the original cost is restored.

Procedure

  1. Run system-view

    The system view is displayed.

  2. Run interface eth-trunk trunk-id

    The Eth-Trunk interface view is displayed.

  3. Run ospf cost-fallback fallbackcost threshold fallbackbw

    A fallback cost is configured for an Eth-Trunk interface.

  4. Run commit

    The configuration is committed.

Verifying the Configuration of OSPF Route Selection

After OSPF route selection is adjusted, you can check OSPF routing table and interface information.

Prerequisites

OSPF route selection has been adjusted.

Procedure

  • Run the display ospf [ process-id ] interface [ all | no-peer | interface-type interface-number ] [ verbose ] command to check information about OSPF interfaces.
  • Run the display ospf [ process-id ] routing command to check information about the OSPF routing table.
  • Run the display ospf [ process-id ] ecmp-group command to check information about OSPF ECMP groups

Example

Run the display ospf interface command to view the network types and costs of OSPF interfaces.

<HUAWEI> display ospf interface
          OSPF Process 1 with Router ID 1.1.1.1
                  
 Area: 0.0.0.0               MPLS TE not enabled
 Interface                IP Address      Type      State    Cost    Pri
 GigabitEthernet1/0/0     192.168.1.1     P2P       P-2-P    1       100

Run the display ospf routing command to view the destination addresses and link costs of OSPF routes and whether load balancing is performed among these OSPF routes.

<HUAWEI> display ospf routing
          OSPF Process 1 with Router ID 4.4.4.4

                   Routing Tables

 Routing for Network
 Destination        Cost    Type          NextHop         AdvRouter       Area
 172.16.1.0/24      4       Inter-area    192.168.2.1     2.2.2.2         0.0.0.2
                    4       Inter-area    192.168.2.3     2.2.2.2         0.0.0.2
 192.168.0.0/24     2       Inter-area    192.168.2.1     2.2.2.2         0.0.0.2
 
 Routing for ASEs
 Destination    Cost      Type       Tag         NextHop         AdvRouter
 100.0.0.0/8    1         Type2      1           192.168.2.1     1.1.1.1
 
 Total Nets: 4
 Intra Area: 1  Inter Area: 2  ASE: 1  NSSA: 0
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Updated: 2019-01-04

Document ID: EDOC1100059437

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