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Understanding Automatically Generated ESIs in EVPN Networks

 

Starting with Junos OS Release 18.4R1, you can configure aggregated Ethernet interfaces and aggregated Ethernet logical interfaces to automatically derive Ethernet segment identifiers (ESIs) from the Link Aggregation Control Protocol (LACP) configuration. We support this feature in the following environments:

  • On Juniper Networks devices that support this feature and are multihomed in active-active mode in an EVPN-VXLAN overlay network.

  • On Juniper Networks devices that support this feature and are multihomed in active-standby or active-active mode in an EVPN-MPLS overlay network.

This topic includes the following information:

Benefits

  • In large EVPN-VXLAN and EVPN-MPLS overlay networks, frees you from manually configuring ESIs.

  • Eliminates the possibility of inadvertently configuring the same ESI for multiple Ethernet segments.

Automatic ESI Configuration

In general, you can configure ESIs on aggregated Ethernet interfaces and aggregated Ethernet logical interfaces using the following methods:

  • Method 1—You can configure automatic ESI on an aggregated Ethernet interface on which LACP is enabled. In this case, an ESI is generated, and that particular ESI is assigned to all logical interfaces on the aggregated Ethernet interface.

  • Method 2—You can configure automatic ESI on one or more logical interfaces of an aggregated Ethernet interface on which LACP is configured. In this case, an ESI is generated for each logical interface on which the feature is enabled and assigned to that particular logical interface.

  • Method 3—On an aggregated Ethernet interface on which LACP is enabled, you can manually configure an ESI using the esi identifier configuration statement at the [edit interfaces aeX] hierarchy level. On one or more logical interfaces on that particular aggregated Ethernet interface, you can configure automatic ESI. In this case, an ESI is generated for each logical interface on which the feature is enabled and assigned to that particular logical interface.

Table 1 outlines the automatic ESI configuration options, how to configure each option, and how the ESI is derived for each option.

Table 1: Automatic ESI Configuration Options

Configuration Options

How to Configure Automatic ESI

How ESI Is Derived

Configure automatic ESI on an aggregated Ethernet interface on which LACP is enabled.

Include the auto-derive and lacp configuration statements at the [edit interfaces aeX esi] hierarchy level.

The ESI is derived from the configured values for the system-id and admin-key configuration statements at the [edit interfaces aeX aggregated-ether-options lacp] hierarchy level.

Configure automatic ESI on an aggregated Ethernet logical interface. LACP is enabled on the parent aggregated Ethernet interface.

Include the auto-derive and lacp configuration statements at the [edit interfaces aeX unit logical-unit-number esi] hierarchy level.

The ESI is derived from the configured values for the system-id configuration statement at the [edit interfaces aeX aggregated-ether-options lacp] hierarchy level and the vlan-id configuration statement at the [edit interfaces aeX unit logical-unit-number] hierarchy level. If a logical interface is configured as a trunk interface (interface-mode trunk) and has a VLAN ID list associated with it, the lowest VLAN ID value is used.

When implementing the automatic ESI feature, keep the following in mind:

  • In your EVPN-VXLAN or EVPN-MPLS overlay network, you can configure automatic ESI using a mix of method 1, 2, and 3 configuration use cases.

  • If a local device is multihomed to two remote devices, we recommend that the aggregated Ethernet and aggregated Ethernet logical interfaces by which the three devices are multihomed have the automatic ESI feature enabled. If the automatic ESI feature is not enabled on one of the interfaces, that interface is not considered during the designated forwarder (DF) election process.

  • The automatically generated ESI is supported in both modulo operation- and preference-based DF election processes.

  • If you enable the automatic ESI feature and manually configure an ESI on a particular aggregated Ethernet interface or aggregated Ethernet logical interface, you will receive an error when you try to commit the configuration.

  • If you enable the automatic ESI feature on an aggregated Ethernet interface and one or more of the logical interfaces on that particular aggregated Ethernet interface, you will receive an error when you try to commit the configuration.

Method 1 Sample Configuration—Automatic ESI on An Aggregated Ethernet Interface

The following example shows the configuration of automatic ESI on aggregated Ethernet interface ae0, which is multihomed in active-active mode. This configuration results in an ESI that is automatically generated based on the LACP configuration and assigned to logical interfaces ae0.0, ae0.100, ae0.101, and ae0.102.

user@mx240> show configuration interfaces ae0

Method 2 Sample Configuration—Automatic ESI On Aggregated Ethernet Logical Interfaces

The following example shows the configuration of automatic ESI on aggregated Ethernet logical interfaces ae0.0, ae0.100, ae0.101, and ae0.102, all of which are multihomed in active-active mode. This configuration results in ESIs that are automatically generated based on the LACP and VLAN ID configurations and assigned to each respective logical interface.

user@mx240> show configuration interfaces ae0

Method 3 Sample Configuration—Manual ESI on Aggregated Ethernet Interface and Automatic ESI on Logical Interfaces

The following example shows the manual configuration of an ESI on aggregrated Ethernet interface ae0, and the configuration of automatic ESI on logical interfaces ae0.0, ae0.100, ae0.101, and ae0.102. All interfaces are multihomed in active-active mode. This configuration results in ESI 00:11:22:33:44:55:66:77:88:99 being assigned to ae0, and ESIs that are automatically generated based on the LACP and VLAN ID configurations and assigned to the respective logical interfaces.

user@mx240> show configuration interfaces ae0

ESI Value Format

When the automatic ESI feature is configured, the aggregated Ethernet and aggregated Ethernet logical interfaces derive the ESIs from various configurations on the aggregated Ethernet interface. The 10-byte format in which the ESI value is stored and propagated is shown in Figure 1.

Figure 1: ESI Value Format
ESI Value Format

The fields of the ESI format are as follows:

  • T—This field is encoded as 0x01, or Type 1, which indicates that the following 9-octet ESI value is automatically generated from the LACP configuration on the interface.

  • CE LACP System MAC address—This 6-octet field includes the system MAC address, which is derived from the value of the system-id configuration statement at the [edit interfaces aeX aggregated-ether-options lacp] hierarchy level.

  • CE LACP Port Key—This 2-octet field includes one of the following:

    • If automatic ESI is configured on an aggregated Ethernet interface, the port key, which is derived from the value of the admin-key configuration statement at the [edit interfaces aeX aggregated-ether-options lacp] hierarchy level.

    • If automatic ESI is configured on an aggregated Ethernet logical interface, the value of the vlan-id configuration statement at the [edit interfaces aeX unit logical-unit-number] hierarchy level.

  • 0—This 1-octet field is encoded as 0x00.

Release History Table
Release
Description
Starting with Junos OS Release 18.4R1, you can configure aggregated Ethernet interfaces and aggregated Ethernet logical interfaces to automatically derive Ethernet segment identifiers (ESIs) from the Link Aggregation Control Protocol (LACP) configuration.