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Example: Prevention of Loops in Bridge Domains by Enabling the MAC Pinnning Feature on Trunk Interfaces

date_range 23-Nov-23

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This example shows how to avoid loops in bridge domains by enabling the MAC pinning feature on trunk interfaces.

Requirements

This example uses the following hardware and software components:

MX Series 5G Universal Routing Platforms
Junos OS Release 16.1 running on the routers

Overview

A MAC move occurs when a MAC address frequently appears on a different physical interface than the one it was learned on. Frequent MAC moves indicate the presence of loops. Loops can occur in Layer 2 bridges and in VPLS networks. To avoid loops, you can enable the MAC pinning feature on the interfaces. The MAC pinning feature is applicable only when dynamic learning of MAC addresses over interfaces is enabled.

This example shows how to enable MAC pinning on three aggregated trunk interfaces in a bridge domain.

Topology

In this example, you configure the interfaces xe-0/1/1 and xe-0/3/1 on the MX Series router as an aggregated Ethernet interface, ae1. You can configure the other four interfaces, ge-4/0/6, ge-4/1/6, xe-4/2/0, and xe-4/3/0, as aggregated Ethernet interfaces, ae2 and ae3. Each of these aggregated Ethernet interfaces are configured as trunk interfaces. Trunk interfaces accept only tagged packets and forward the packets within a specified bridge domain, BD_Trunk_all. Specify the list of VLAN IDs for the interfaces and the bridge domain. When a tagged packet is received on any of the aggregated trunk interfaces, the packet is accepted, and the packet is forwarded within the bridge domain that is configured with the matching ID.

In the bridge domain, after specifying the VLAN ID, specify 131000 as the maximum number of MAC addresses that can be learned on each of the aggregated Ethernet trunk interfaces and specify 1048575 as the size of the MAC address table for the bridge domain or VLAN.

In this topology, frequent MAC moves can occur, which can result in loops. To prevent these loops, you can configure MAC pinning. When you configure MAC pinning on an interface, the MAC address learned on the interface cannot be learned on another interface in the same bridge domain. For example, configure MAC pinning on the aggregated Ethernet interface ae1. When a packet is received on this interface, the packet is accepted, and the packet is forwarded within the bridge domain with the matching ID. However, if a packet with the same MAC address is received on any other trunk interface, say ae2, the packet is discarded or dropped as that MAC address is pinned to the trunk interface ae1. This behavior is common to all trunk interfaces configured on the router, regardless of whether access pinning is enabled on the trunk interface or not.

CLI Quick Configuration

To quickly configure this example, copy the following commands, paste them into a text file, remove any line breaks, change any details necessary to match your network configuration, and then copy and paste the commands into the CLI at the [edit] hierarchy level.

content_copy zoom_out_map
set interfaces xe-0/1/1 gigether-options 802.3ad ae1
set interfaces xe-0/3/1 gigether-options 802.3ad ae1
set interfaces ge-4/0/6 gigether-options 802.3ad ae3
set interfaces ge-4/1/6 gigether-options 802.3ad ae3
set interfaces xe-4/2/0 gigether-options 802.3ad ae2
set interfaces xe-4/3/0 gigether-options 802.3ad ae2
set interfaces ae1 flexible-vlan-tagging 
set interfaces ae1 encapsulation flexible-ethernet-services
set interfaces ae1 unit 0 family bridge interface-mode trunk 
set interfaces ae1 unit 0 family bridge vlan-id-list 1-5
set interfaces ae2 flexible-vlan-tagging 
set interfaces ae2 encapsulation flexible-ethernet-services
set interfaces ae2 unit 0 family bridge interface-mode trunk 
set interfaces ae2 unit 0 family bridge vlan-id-list 1-5
set interfaces ae3 flexible-vlan-tagging 
set interfaces ae3 encapsulation flexible-ethernet-services
set interfaces ae3 unit 0 family bridge interface-mode trunk 
set interfaces ae3 unit 0 family bridge vlan-id-list 1-5
set bridge-domains BD_Trunk_all vlan-id-list 1-5
set bridge-domains BD_Trunk_all bridge-options mac-table-size 1048575
set bridge-domains BD_Trunk_all bridge-options interface ae1.0 interface-mac-limit 131000
set bridge-domains BD_Trunk_all bridge-options interface ae2.0 interface-mac-limit 131000
set bridge-domains BD_Trunk_all bridge-options interface ae3.0 interface-mac-limit 131000
set switch-options interface ae1.0 interface-mac-limit 131000
set switch-options interface ae1.0 mac-pinning
set switch-options interface ae2.0 interface-mac-limit 131000
set switch-options interface ae2.0 mac-pinning
set switch-options interface ae3.0 interface-mac-limit 131000
set switch-options interface ae3.0 mac-pinning

Procedure

Step-by-Step Procedure

The following example requires you to navigate various levels in the configuration hierarchy. For information about navigating the CLI, see Using the CLI Editor in Configuration Mode

To configure MAC pinning on trunk interfaces in bridge domains:

Configure the interfaces as member aggregated Ethernet interfaces.

content_copy zoom_out_map
[edit interfaces]
user@host# set interfaces xe-0/1/1 gigether-options 802.3ad ae1
user@host# set interfaces xe-0/3/1 gigether-options 802.3ad ae1
user@host# set interfaces ge-4/0/6 gigether-options 802.3ad ae3
user@host# set interfaces ge-4/1/6 gigether-options 802.3ad ae3
user@host# set interfaces xe-4/2/0 gigether-options 802.3ad ae2
user@host# set interfaces xe-4/3/0 gigether-options 802.3ad ae2

Configure the aggregated Ethernet interfaces as trunk interfaces and specify the list of VLAN IDs.

content_copy zoom_out_map
user@host# set interfaces ae1 flexible-vlan-tagging
user@host# set interfaces ae1 encapsulation flexible-ethernet-services
user@host# set interfaces ae1 unit 0 family bridge interface-mode trunk
user@host# set interfaces ae1 unit 0 family bridge vlan-id-list 1-5
user@host# set interfaces ae2 flexible-vlan-tagging
user@host# set interfaces ae2 encapsulation flexible-ethernet-services
user@host# set interfaces ae2 unit 0 family bridge interface-mode trunk
user@host# set interfaces ae2 unit 0 family bridge vlan-id-list 1-5
user@host# set interfaces ae3 flexible-vlan-tagging
user@host# set interfaces ae3 encapsulation flexible-ethernet-services
user@host# set interfaces ae3 unit 0 family bridge interface-mode trunk
user@host# set interfaces ae3 unit 0 family bridge vlan-id-list 1-5

Specify the name of the bridge domain.

content_copy zoom_out_map
[edit bridge-domains]
user@host# set bridge-domains BD_Trunk_all vlan-id-list 1-5

Specify the size of the MAC address table for the bridge domain.
```
user@host#  set bridge-domains BD_Trunk_all bridge-options mac-table-size 1048575
```

Specify the maximum number of MAC addresses that can be learned on all three trunk interfaces.

content_copy zoom_out_map
user@host# set bridge-domains BD_Trunk_all bridge-options interface ae1.0 interface-mac-limit 131000
user@host#  set bridge-domains BD_Trunk_all bridge-options interface ae2.0 interface-mac-limit 131000
user@host#  set bridge-domains BD_Trunk_all bridge-options interface ae3.0 interface-mac-limit 131000

Configure MAC pinning on each of the aggregated Ethernet interfaces at the [edit switch-options] hierarchy level.

content_copy zoom_out_map
[edit switch-options]
user@host# set switch-options interface ae1.0 interface-mac-limit 131000
user@host# set switch-options interface ae1.0 mac-pinning
user@host# set switch-options interface ae2.0 interface-mac-limit 131000
user@host# set switch-options interface ae2.0 mac-pinning
user@host# set switch-options interface ae3.0 interface-mac-limit 131000
user@host# set switch-options interface ae3.0 mac-pinning

Results

From configuration mode, confirm your configuration by entering show interfaces and show bridge-domains commands. If the output does not display the intended configuration, repeat the instructions in this example to correct the configuration.

content_copy zoom_out_map
user@host# show interfaces
interfaces {
    xe-0/0/0 {
        flexible-vlan-tagging;
        encapsulation flexible-ethernet-services;
        unit 0 {
            family bridge {
                interface-mode trunk;
                vlan-id-list 1-5;
            }
        }
    }
    xe-0/1/1 {
        gigether-options {
            802.3ad ae1;
        }
    }
    xe-0/3/1 {
        gigether-options {
            802.3ad ae1;
        }
    }
    ge-4/0/6 {
        gigether-options {
            802.3ad ae3;
        }
    }
    ge-4/1/6 {
        gigether-options {
            802.3ad ae3;
        }
    }
    xe-4/2/0 {
        gigether-options {
            802.3ad ae2;
        }
    }
    xe-4/3/0 {
        gigether-options {
            802.3ad ae2;
        }
    }
    ae1 {
        flexible-vlan-tagging;
        encapsulation flexible-ethernet-services;
        unit 0 {
            family bridge {
                interface-mode trunk;
                vlan-id-list 1-5;
            }
        }
    }
    ae2 {
        flexible-vlan-tagging;
        encapsulation flexible-ethernet-services;
        unit 0 {
            family bridge {
                interface-mode trunk;
                vlan-id-list 1-5;
            }
        }
    }
    ae3 {
        flexible-vlan-tagging;
        encapsulation flexible-ethernet-services;
        unit 0 {
            family bridge {
                interface-mode trunk;
                vlan-id-list 1-5;
            }
        }
    }
}
 
user@host# show bridge-domains
bridge-domains {
    BD_Trunk_all {
        vlan-id-list 1-5;
        bridge-options {
            mac-table-size {
                1048575;
            }
            interface ae1.0 {
                interface-mac-limit {
                    131000;
                }
            }
            interface ae2.0 {
                interface-mac-limit {
                    131000;
                }
            }
            interface ae3.0 {
                interface-mac-limit {
                    131000;
                }
            }
        }
    }
}

user@host# show switch-options
switch-options {
    interface ae1.0 {
        interface-mac-limit {
            131000;
        }
        mac-pinning;
    }
    interface ae2.0 {
        interface-mac-limit {
            131000;
        }
        mac-pinning;
    }
    interface ae3.0 {
        interface-mac-limit {
            131000;
        }
        mac-pinning;
    }
}

If you have completed configuring the device, enter commit from the configuration mode.

Verification

Verifying that MAC Pinning Is Configured Correctly

Purpose
Action
Meaning

Purpose

Ensure that MAC pinning is enabled on the trunk interfaces.

Action

From operational mode, enter the show l2-learning interfacecommand.

content_copy zoom_out_map
user@host> show l2-learning interface 
Routing Instance Name : default-switch
Logical Interface flags (DL -disable learning, AD -packet action drop,
                         LH - MAC limit hit, DN - Interface Down, MP - MAC Pinning)
Logical             BD         MAC        STP          Logical
Interface           Name       Limit      State        Interface flags  
xe-0/0/0.0                     8192                   
                    BD_Tru..   1024       Forwarding  
                    BD_Tru..   1024       Forwarding  
                    BD_Tru..   1024       Forwarding  
                    BD_Tru..   1024       Forwarding  
                    BD_Tru..   1024       Forwarding  
Routing Instance Name : default-switch
Logical Interface flags (DL -disable learning, AD -packet action drop,
                         LH - MAC limit hit, DN - Interface Down, MP - MAC Pinning)
Logical             BD         MAC        STP          Logical
Interface           Name       Limit      State        Interface flags  
ae1.0                          131000                               MP
                    BD_Tru..   131000     Forwarding  
                    BD_Tru..   131000     Forwarding  
                    BD_Tru..   131000     Forwarding  
                    BD_Tru..   131000     Forwarding  
                    BD_Tru..   131000     Forwarding  
Routing Instance Name : default-switch
Logical Interface flags (DL -disable learning, AD -packet action drop,
                         LH - MAC limit hit, DN - Interface Down, MP - MAC Pinning)
Logical             BD         MAC        STP          Logical
Interface           Name       Limit      State        Interface flags  
ae2.0                          131000                               MP
                    BD_Tru..   131000     Forwarding  
                    BD_Tru..   131000     Forwarding  
                    BD_Tru..   131000     Forwarding  
                    BD_Tru..   131000     Forwarding  
                    BD_Tru..   131000     Forwarding  
Routing Instance Name : default-switch
Logical Interface flags (DL -disable learning, AD -packet action drop,
                         LH - MAC limit hit, DN - Interface Down, MP - MAC Pinning)
Logical             BD         MAC        STP          Logical
Interface           Name       Limit      State        Interface flags  
ae3.0                          131000                               MP
                    BD_Tru..   131000     Forwarding  
                    BD_Tru..   131000     Forwarding  
                    BD_Tru..   131000     Forwarding  
                    BD_Tru..   131000     Forwarding  
                    BD_Tru..   131000     Forwarding  

Meaning

The Interface flags field indicates the interfaces that have MAC pinning enabled.

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Layer 2 VPNs and VPLS User Guide for Routing Devices

ON THIS PAGE

Example: Prevention of Loops in Bridge Domains by Enabling the MAC Pinnning Feature on Trunk Interfaces

Requirements

Overview

Topology

Configuration

CLI Quick Configuration

Procedure

Step-by-Step Procedure

Results

Verification

Verifying that MAC Pinning Is Configured Correctly

Purpose

Action

Meaning

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Layer 2 VPNs and VPLS User Guide for Routing Devices

ON THIS PAGE

Example: Prevention of Loops in Bridge Domains by Enabling the MAC Pinnning Feature on Trunk Interfaces

Requirements

Overview

Topology

Configuration

CLI Quick Configuration

Procedure

Step-by-Step Procedure

Results

Verification

Verifying that MAC Pinning Is Configured Correctly

Purpose

Action

Meaning

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