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Configuration Guide - VPN 01

NE05E and NE08E V300R003C10SPC500

This is NE05E and NE08E V300R003C10SPC500 Configuration Guide - VPN
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Configuring EVPN Reliability

Configuring EVPN Reliability

This section describes how to configure Ethernet VPN (EVPN) reliability functions.

Usage Scenario

Reliability Function

Scenario

Configuring EVPN BGP Peer Status Tracking

On an EVPN where a CE is dual-homed to PEs, after a PE restarts due to a fault or other reasons, traffic may be lost. As shown in Figure 11-9, CE1 is dual-homed to PE1 and PE2, and PE1 is elected as the primary designated forwarder (DF). If PE1 fails, PE2 becomes the primary DF and takes over the broadcast, unknown unicast, and multicast (BUM) traffic. After PE1 recovers, if PE1 sets up a BGP peer relationship with PE2 before with PE3, PE1 exchanges Ethernet segment (ES) routes with PE2 and restores to be the primary DF, and PE2 becomes the backup DF again. In this case, if PE3 still forwards the BUM traffic to PE2, the traffic will be discarded. However, if PE1 sets up a BGP peer relationship with PE3 before with PE2, PE1 and PE2 both become the primary DFs, in which case, PE3 forwards the BUM traffic to both PE1 and PE2, causing CE1 to receive duplicate copies of traffic.

To resolve this issue, configure PE1's interface connecting to CE1 to track the EVPN BGP peer status.

This configuration allows PE1 to trigger a delay timer for ES route advertisement after PE1 recovers and PE1's interface connecting to CE1 goes Up. After the delay timer is triggered, PE1 tracks the status of its BGP peers PE2 and PE3. If the BGP peer relationships both go Up within the timer-specified delay, PE1 sends ES routes to PE2 and PE3. If the timer-specified delay elapses, PE1 sends ES routes only to the peer with which the BGP peer relationship is Up. After PE1 generates and sends ES routes, PE1 performs DF election based on all the received ES routes.

NOTE:

The delay after which ES routes are sent must be set according to the BGP peer relationship status. If a BGP peer relationship is not set up after the delay elapses, two primary or backup DFs exist. In the case of two primary DFs, duplicate copies of traffic are sent. In the case of two backup DFs, the traffic is discarded.

Figure 11-9 CE dual-homing networking

Setting a Delay After Which ES Routes Are Advertised

If the PE functioning as the primary DF recovers from a fault, the traffic on the network side may be lost due to the slow connection recovery on the access side. As shown in Figure 11-10, at least one of PE1 and PE2 is configured to work in the Single-Active redundancy mode. If PE1 fails, the connection between CE1 and PE1 is interrupted, and the Ethernet segment identifier (ESI) configured for the connection to CE1 becomes invalid. As a result, PE1 becomes the backup DF, and PE2 becomes the primary DF. The traffic forwarding path is changed from CE2->PE3->PE1->CE1 to CE2->PE3->PE2->CE1. After PE1 recovers, PE1's ESI becomes valid again, and PE1 generates ES routes immediately for DF election. PE1 becomes the primary DF rapidly, but the connection between CE1 and PE1 still fails to be set up. As a result, CE1 still sends traffic to PE2, causing traffic loss.

To resolve this issue, set on PE1's interface connecting to CE1 a delay after which ES routes are advertised. This configuration allows PE1 to generate ES routes only after the access-side network recovers.

Figure 11-10 CE dual-homing networking

Configuring the Function That the AC Status Influences DF Election on a PE

In CE dual-homing networking, AC sub-interfaces are bound to EVPN instances. If an ESI is configured on the interface and one of the sub-interfaces goes Down due to a fault or some other reason, the ESI remains valid because the other sub-interface bound to the EVPN instance remain Up. As a result, the PE does not regenerate ES routes to trigger DF election, which may prevent the BUM traffic from being forwarded.

To resolve this issue, enable the function that the AC interface status influences DF election. This configuration helps check whether the system has received the Auto Discovery (AD) routes from all the PEs during DF election to determine whether they are qualified for DF election. If the system has not received the AD routes from a PE, this PE cannot participate in DF election.

Configuring a Delay for a Public-Network Outbound Interface to Go Up

In a scenario where a VLL accesses an EVPN in active-active mode, when the backup PE restarts, BUM traffic can still be forwarded due to the unstable status. As a result, extra packets occur. To resolve this issue, configure a delay on all public network outbound interfaces of the VLL on the backup PE so that the outbound interfaces can go Up only after the delay expires. Setting a 5-minute delay for an interface to go Up is recommended.

Pre-configuration Tasks

Before configuring EVPN reliability functions, Configuring Common EVPN Functions.

Perform the following steps on a PE:

Procedure

  • Configure the function of tracking the BGP EVPN peer status on a PE.
    1. Run system-view

      The system view is displayed.

    2. Run interface eth-trunk trunk-id

      The Eth-Trunk interface view is created and displayed.

    3. Run es track evpn-peersource-address

      The function of tracking the EVPN BGP peer status is configured. To track the status of multiple EVPN BGP peers, repeat this step.

    4. Run commit

      The configuration is committed.

  • Set a delay after which ES routes are advertised on a PE.
    1. Run system-view

      The system view is displayed.

    2. Run interface eth-trunk trunk-id

      The Eth-Trunk interface view is created and displayed.

    3. Run timer es-recovery interval

      A delay after which ES routes are advertised is set. The recommended value is 30s.

    4. Run commit

      The configuration is committed.

  • Configure the function that the AC status influences DF election on the PE.
    1. Run system-view

      The system view is displayed.

    2. Run evpn

      The global EVPN configuration view is created and displayed.

    3. Run df-election ac-influence enable

      The function that the AC interface status influences DF election is enabled on the PE.

    4. Run commit

      The configuration is committed.

  • Configure a delay for a public-network outbound interface to go Up.
    1. Run system-view

      The system view is displayed.

    2. Run interface interface-type interface-number

      The view of a specified interface is displayed.

    3. Run carrier up-hold-time interval

      A delay for the interface to go Up is set.

    4. Run commit

      The configuration is committed.

Checking the Configurations

Run the display current-configuration command to check whether the reliability functions are configured successfully.

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Updated: 2019-01-14

Document ID: EDOC1100058925

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