Juniper Aggregated Ethernet Interfaces


In this blog, we’ll be discussing one of the most High Availability protocols that’s broadly used in today’s networks that is Link Aggregation Control Protocol (LACP) and Link Aggregation Groups (ALG)

LACP is a method of bundling several physical interfaces to form one logical interface, which is advantageous in providing more bandwidth and increasing redundancy, On Cisco devices this is referred to as Ether-Channel.

It’s worth noting that the load-balancing hash algorithm for IP traffic uses criteria at Layer 2, Layer 3, and Layer 4. No configuration is necessary to enable load balancing. The load-balancing hash algorithm for non-IP traffic uses source and destination MAC addresses.

LACP exchanges are made between actors and partners. An actor is the local interface in an LACP exchange. A partner is the remote interface in an LACP exchange. LACP is defined in IEEE 802.3ad,  Aggregation of Multiple Link Segments and was designed to achieve the following:

  • Automatic addition and deletion of individual links to the aggregate bundle without user intervention
  • Link monitoring to check whether both ends of the bundle are connected to the correct group

Note that the Junos OS implementation of LACP provides link monitoring but not automatic addition and deletion of links.

The LACP mode can be active or passive. By default, when LACP is configured its mode defaults to the passive mode on aggregated Ethernet interfaces. To initiate transmission of LACP packets and response to LACP packets, you must enable LACP active mode.

Note that LACP exchanges protocol data units (PDUs) across all member links to ensure each physical interfaces is configured and functioning properly.

Platform Support for Aggregated Ethernet Interfaces

The following routers support a maximum of 16 physical interfaces per single aggregated Ethernet bundle:

  • M120
  • M320
  • All MX Series 3D Universal Edge Routers
  • All T Series routers

All other routers support a maximum of 8 physical interfaces per aggregated Ethernet bundle.

You can refer to below link for more info about platform support.

Maximum Interfaces per LAG and Maximum LAGs per Switch/Router

Configuring Aggregated Ethernet Links

Specify the number of aggregated Ethernet interfaces to be created:

[edit chassis]
user@switch# set aggregated-devices ethernet device-count 3

This process is straightforward if you must configure interfaces ae0, ae1, and ae2 on the router. However, if you must configure only interface ae2 on the local router, the answer is not as simple to ascertain. Although only one aggregated Ethernet interface now exists, you must set the aggregated device count to 3, as setting the aggregated device count to 1 results in the creation of interface ae0—interface ae2 is not created.

Specify the minimum number of links for the aggregated Ethernet interface (aex), that is, the defined bundle, to be labeled up:

[edit interfaces]
user@switch# set ae0 aggregated-ether-options minimum-links 2

The minimum-links statement monitors the member links in the bundle and takes the entire bundle down if the operational member links fall below the configured threshold. You must configure this statement on both ends of the bundle.

Specify the members to be included within the aggregated Ethernet bundle:

[edit interfaces]
user@switch# set ge-0/0/0 ether-options 802.3ad ae0
user@switch# set ge-0/0/1 ether-options 802.3ad ae0

Specify an interface family for the aggregated Ethernet bundle:

[edit interfaces]
user@switch# set ae0 unit 0 family inet address


edit interfaces]
user@switch# set ae0 unit 0 family ethernet-switching port-mode trunk members all

Configuring Aggregated Ethernet LACP

Configure at least one side of the aggregated Ethernet link as active:

[edit interfaces]
user@switch# set ae0 aggregated-ether-options lacp active

Specify the interval at which the interfaces send LACP packets:

[edit interfaces]
user@switch# set ae0 aggregated-ether-options lacp periodic 10

The interval can be fast (every second) or slow (every 30 seconds). You can configure different periodic rates on active and passive interfaces. When you configure the active and passive interfaces at different rates, the transmitter honors the receiver’s rate.


Verify your L3 LACP LAG by viewing the LACP interface status:

root@Switch> show lacp interfaces
Aggregated interface: ae0
    LACP state     Role     Exp   Def  Dist  Col  Syn  Aggr  Timeout  Activity
      ge-0/0/0      Actor    No    No   Yes  Yes  Yes   Yes     Fast    Active
      ge-0/0/0    Partner    No    No   Yes  Yes  Yes   Yes     Fast   Passive
      ge-0/0/1      Actor    No    No   Yes  Yes  Yes   Yes     Fast    Active
      ge-0/0/1    Partner    No    No   Yes  Yes  Yes   Yes     Fast   Passive
    LACP protocol:        Receive State  Transmit State            Mux State 
      ge-0/0/0                 Current   Fast periodic Collecting distributing
      ge-0/0/1                 Current   Fast periodic Collecting distributing


Use the show lacp statistics interfaces interface-name command to display LACP BPDU exchange information.

root@Switch> show lacp statistics interfaces ae0
Aggregated interface: ae0
    LACP Statistics:       LACP Rx     LACP Tx   Unknown Rx   Illegal Rx 
      ge-0/0/0                1352        2035            0            0
      ge-0/0/1                1352        2056            0            0

You can also use the show interfaces ae0 detail command in user mode. This command will display the member interfaces and member interface statistics.

root@Switch> show interfaces ae0 detail
Physical interface: ae0, Enabled, Physical link is Up
  Interface index: 153, SNMP ifIndex: 553, Generation: 156
  Link-level type: Ethernet, MTU: 1514, Speed: 2Gbps, BPDU Error: None,
  MAC-REWRITE Error: None, Loopback: Disabled, Source filtering: Disabled,
  Flow control: Disabled, Minimum links needed: 1, Minimum bandwidth needed: 0
  Device flags   : Present Running
  Interface flags: SNMP-Traps Internal: 0x0
  Current address: 00:23:9c:1a:a3:43, Hardware address: 00:23:9c:1a:a3:43
  Last flapped   : 2013-09-13 03:54:38 EDT (02:16:40 ago)
  Statistics last cleared: Never
  Traffic statistics:
   Input  bytes  :               238977                    0 bps
   Output bytes  :               994114                    0 bps
   Input  packets:                 1497                    0 pps
   Output packets:                 9294                    0 pps
   IPv6 transit statistics:
    Input  bytes  :                   0
    Output bytes  :                   0
    Input  packets:                   0
    Output packets:                   0

  Logical interface ae0.0 (Index 93) (SNMP ifIndex 554) (HW Token 4294967295)
   (Generation 162)
    Flags: SNMP-Traps 0x0 Encapsulation: ENET2
    Statistics        Packets        pps         Bytes          bps
        Input :            33          0          2758            0
        Output:            39          0          2970            0
    Adaptive Statistics:
        Adaptive Adjusts:          0
        Adaptive Scans  :          0
        Adaptive Updates:          0
    Marker Statistics:   Marker Rx     Resp Tx   Unknown Rx   Illegal Rx
      ge-0/0/0.0                0           0            0            0
      ge-0/0/1.0                0           0            0            0
    Protocol eth-switch, Generation: 179, Route table: 0
      Flags: Trunk-Mode

I hope this was informative and thanks for viewing.



Posted on September 3, 2016, in Juniper and tagged , , , , . Bookmark the permalink. Leave a comment.

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