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NE40E V800R010C10SPC500 Configuration Guide - IP Routing 01

This is NE40E V800R010C10SPC500 Configuration Guide - IP Routing
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Configuring IPv4 IS-IS to Interact with Other Routing Protocols

Configuring IPv4 IS-IS to Interact with Other Routing Protocols

If other routing protocols are configured on an IS-IS network, configure IS-IS to interact with these protocols for communication between them.

Usage Scenario

If other routing protocols are configured on an IS-IS network, note the following issues:
  • Priorities of IS-IS routes

    If multiple routes to the same destination are discovered by different routing protocols running on the same device, the route discovered by the protocol with the highest priority is selected. For example, if both OSPF and IS-IS are configured, the route discovered by OSPF is used because OSPF enjoys a higher priority than IS-IS by default.

    If you want the route discovered by IS-IS to be preferentially selected, configure a higher priority for the route.

  • Communication between areas

    If other routing protocols are configured on an IS-IS network, configure IS-IS to interact with those routing protocols so that IS-IS areas can communicate with non-IS-IS areas.
    NOTE:

    The LSDBs of different IS-IS processes on a device are independent of each other. Therefore, each IS-IS process on the device considers routes of the other IS-IS processes as external routes.

    To ensure successful traffic forwarding, configure IS-IS to import external routes on a device (such as a Level-1-2 IS-IS router) where external routes are configured. Such configuration enables all devices in IS-IS areas to learn external routes, implementing refined control over traffic forwarding.

    To ensure successful forwarding of traffic destined for IS-IS areas, enable the other routing protocols to interact with IS-IS.

Pre-configuration Tasks

Before configuring IPv4 IS-IS to interact with other routing protocols, 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.

  • Configure basic functions of other routing protocols.

Configuration Procedures

Perform one or more of the following configurations as required.

Configuring a Preference Value for IPv4 IS-IS

If multiple routes to the same destination are discovered by different routing protocols, configure the highest priority value for IS-IS so that a route discovered by IS-IS can be selected preferentially.

Context

If multiple routes to the same destination are discovered by different routing protocols running on the same device, the route discovered by the protocol with the highest priority is selected.

For example, if both OSPF and IS-IS are configured on a network, the route discovered by OSPF is used because OSPF has a higher priority than IS-IS by default.

To prefer a route discovered by IS-IS, configure a higher priority value for IS-IS. In addition, you can configure a routing policy to increase the priority of specified IS-IS routes, without affecting route selection.

Procedure

  • Configure the IS-IS priority value.
    1. Run system-view

      The system view is displayed.

    2. Run isis [ process-id ]

      The IS-IS view is displayed.

    3. Run preference preference

      The IS-IS priority value is configured.

      NOTE:

      A smaller preference value indicates a higher preference.

    4. Run commit

      The configuration is committed.

  • Configure a priority value for specified IS-IS routes.
    1. Run system-view

      The system view is displayed.

    2. Run isis [ process-id ]

      The IS-IS view is displayed.

    3. Run preference preference route-policy route-policy-name

      The priority value is configured for the specified IS-IS routes.

      NOTE:

      preference takes effect only on IS-IS routes that match the specified routing policy.

    4. Run commit

      The configuration is committed.

Configuring IPv4 IS-IS to Import External Routes

If devices in an IS-IS routing domain need to learn external routes, configure IS-IS on a Level-1-2 device of this routing domain to import external routes.

Context

If a Level-1-2 device is configured to advertise a default route, all traffic destined beyond the routing domain is forwarded by this Level-1-2 device because the other devices in the IS-IS routing domain do not have external routes. As a result, this Level-1-2 device will be overloaded.

If multiple Level-1-2 devices are deployed, optimal routes to other routing domains need to be selected. To ensure optimal routes are selected, all the other devices in the IS-IS routing domain must learn all or some external routes.

Routing policies can be configured to import or advertise external routes that meet specified conditions to the IS-IS routing domain.

Procedure

  • Configure IS-IS to import external routes.
    1. Run system-view

      The system view is displayed.

    2. Run isis [ process-id ]

      The IS-IS view is displayed.

    3. Configure IS-IS to import external routes.

      • To import external routes and set a cost for them, run the import-route { direct | static | unr | { ospf | rip | isis } [ process-id ] | bgp [ permit-ibgp ] } [ cost-type { external | internal } | cost cost | tag tag | route-policy route-policy-name | [ level-1 | level-2 | level-1-2 ] ] * command.

      • To import external routes and keep the original costs, run the import-route { { ospf | rip | isis } [ process-id ] | bgp [ permit-ibgp ] | direct } inherit-cost [ tag tag | route-policy route-policy-name | [ level-1 | level-2 | level-1-2 ] ] * command. When configuring IS-IS to retain the original costs of imported routes, the source routes cannot be static.

      NOTE:

      IS-IS advertises all imported external routes to an IS-IS routing domain by default.

      If only some imported external routes need to be advertised, run the filter-policy export command to set a filtering policy.

    4. Run commit

      The configuration is committed.

  • Configure IS-IS to advertise some external routes to an IS-IS routing domain.
    1. Run system-view

      The system view is displayed.

    2. Run isis [ process-id ]

      The IS-IS view is displayed.

    3. Configure to advertise specified external routes to the IS-IS routing domain.

      Run any of the following commands as required:

      • Based on the basic ACL:
        1. Run filter-policy { acl-number | acl-name acl-name } export [ protocol [ process-id ] ]

        2. Run quit

          Return to the system view.

        3. Run acl { name basic-acl-name { basic | [ basic ] number basic-acl-number } | [ number ] basic-acl-number } [ match-order { config | auto } ]

          The basic ACL view is displayed.

        4. Run rule [ rule-id ] [ name rule-name ] { deny | permit } [ fragment-type { fragment | non-fragment | non-subseq | fragment-subseq | fragment-spe-first } | source { source-ip-address { source-wildcard | 0 | src-netmask } | any } | time-range time-name | vpn-instance vpn-instance-name ] *

          The rule for the basic ACL is configured.

          When the rule command is run to configure rules for a named ACL, only the source address range specified by source and the time period specified by time-range are valid as the rules.

          When a filtering policy of a routing protocol is used to filter routes:
          • If the action specified in an ACL rule is permit, a route that matches the rule will be received or advertised by the system.

          • If the action specified in an ACL rule is deny, a route that matches the rule will not be received or advertised by the system.

          • If a route has not matched any ACL rules, the route will not be received or advertised by the system.

          • If an ACL does not contain any rules, all routes matching the route-policy that references the ACL will not be received or advertised by the system.

          • If the ACL referenced by the route-policy does not exist, all routes matching the route-policy will be received or advertised by the system.

          • In the configuration order, the system first matches a route with a rule that has a smaller number and then matches the route with a rule with a larger number. Routes can be filtered using a blacklist or a whitelist:

            Route filtering using a blacklist: Configure a rule with a smaller number and specify the action deny in this rule to filter out the unwanted routes. Then, configure another rule with a larger number in the same ACL and specify the action permit in this rule to receive or advertise the other routes.

            Route filtering using a whitelist: Configure a rule with a smaller number and specify the action permit in this rule to permit the routes to be received or advertised by the system. Then, configure another rule with a larger number in the same ACL and specify the action deny in this rule to filter out unwanted routes.

      • Based on the IP prefix:

        Run filter-policy ip-prefix ip-prefix-name export [ protocol [ process-id ] ]

      • Based on the route policy:

        Run filter-policy route-policy route-policy-name export [ protocol [ process-id ] ]

      NOTE:

      After this command is run, only external routes that meet the specified conditions can be advertised to the IS-IS routing domain.

    4. Run commit

      The configuration is committed.

Verifying the Configuration of Interaction Between IPv4 IS-IS and Other Routing Protocols

After configuring IS-IS to import routes from other protocols, check the configurations.

Procedure

  • Run the display isis lsdb [ { level-1 | level-2 } | verbose | { local | lsp-id | is-name symbolic-name } ] * [ process-id | vpn-instance vpn-instance-name ] command to check IS-IS LSDB information.
  • Run the display isis route [ process-id | vpn-instance vpn-instance-name ] [ ipv4 ] [ verbose | [ level-1 | level-2 ] | ip-address [ mask | mask-length ] ] * command to check IS-IS routing information.
  • Run the display ip routing-table ip-prefix ip-prefix-name [ verbose ] command to check the IP routing table.

Example

Run the display isis lsdb verbose command on the device that generates a default route. The command output shows that IS-IS has advertised a default route.

<HUAWEI> display isis lsdb verbose

Run the display isis route command on the device that receives the default route. The command output shows that the default route with next hop address 20.1.1.2 has been added to the Level-2 IS-IS routing table.

<HUAWEI> display isis route
                         Route information for ISIS(1)
                         -----------------------------

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

IPV4 Destination     IntCost    ExtCost ExitInterface   NextHop         Flags
-------------------------------------------------------------------------------
10.1.1.0/24          10         NULL    GE1/0/0         Direct          D/-/L/-
20.1.1.0/24          10         NULL    GE1/0/1         Direct          D/-/L/-
     Flags: D-Direct, A-Added to URT, L-Advertised in LSPs, S-IGP Shortcut,
                               U-Up/Down Bit Set


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

IPV4 Destination     IntCost    ExtCost ExitInterface   NextHop         Flags
-------------------------------------------------------------------------------
0.0.0.0/0           10         NULL    GE1/0/1        20.1.1.2        A/-/-/-
10.1.1.0/24          10         NULL    GE1/0/0          Direct          D/-/L/-
20.1.1.0/24          10         NULL    GE1/0/1          Direct          D/-/L/-
     Flags: D-Direct, A-Added to URT, L-Advertised in LSPs, S-IGP Shortcut,
                               U-Up/Down Bit Set

Run the display isis route command to view the IS-IS routing table. The command output shows that the direct route 192.168.1.0/24 and OSPF route 14.1.1.1/32 have been added to the Level-2 IS-IS routing table.

<HUAWEI> display isis route

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

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

IPV4 Destination     IntCost    ExtCost ExitInterface   NextHop         Flags
-------------------------------------------------------------------------------
10.1.1.0/24          20         NULL    GE1/0/2         20.1.1.1        A/-/-/-
20.1.1.0/24          10         NULL    GE1/0/2         Direct          D/-/L/-
     Flags: D-Direct, A-Added to URT, L-Advertised in LSPs, S-IGP Shortcut,
                               U-Up/Down Bit Set


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

 Type IPV4 Destination     IntCost    ExtCost Tag
-------------------------------------------------------------------------------
 D    192.168.1.0/24      0          20
 O    14.1.1.1/32         0          20

             Type: D-Direct, I-ISIS, S-Static, O-OSPF, B-BGP, R-RIP

Run the display ip routing-table command to view the IP routing table. The command output shows that the value of Preference of IPv4 IS-IS has been changed from its default value 15 to 20.

<HUAWEI> display ip routing-table
Route Flags: R - relay, D - download
to fib, T - to vpn-instance, B - black hole route
------------------------------------------------------------------------------
Routing Tables: Public
         Destinations : 6        Routes : 6

Destination/Mask    Proto   Pre  Cost      Flags NextHop         Interface

       10.1.1.0/24  Direct  0    0           D   10.1.1.1        GigabitEthernet1/0/0
       10.1.1.1/32  Direct  0    0           D   127.0.0.1       InLoopBack0
       10.1.1.2/32  Direct  0    0           D   10.1.1.2        GigabitEthernet1/0/0
       22.2.2.0/24  ISIS-L2 20   10          D   10.1.1.2        GigabitEthernet1/0/0
      127.0.0.0/8   Direct  0    0           D   127.0.0.1       InLoopBack0
      127.0.0.1/32  Direct  0    0           D   127.0.0.1       InLoopBack0

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Updated: 2019-01-03

Document ID: EDOC1100055018

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