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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. Read the rest of this entry