Juniper JUNOSE 11.1.X - LINK LAYER CONFIGURATION 4-7-2010, Configuration Manual

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For information about the modules that support link aggregation, see ERX Module
Guide, Appendix A, Module Protocol Support and E120 and E320 Module Guide, Appendix
A, IOA Protocol Support .
LACP
The Link Aggregation Control Protocol (LACP) is a mechanism for exchanging port
and system information to create and maintain LAG bundles. The LAG bundle
distributes MAC clients across the link layer interface and collects traffic from the
links to present to the MAC clients of the LAG bundle.
To create the links in the LAG bundles, you can add one or more Ethernet physical
interfaces to it. The LACP detects Ethernet interfaces as links if they are configured
on the same line module and have the same physical layer characteristics. The LACP
also assigns to the LAG bundle the same MAC address of the Ethernet link with the
highest port priority, which is the lowest value.
The LACP also controls the exchange of LACP protocol data units (PDUs) between
the Ethernet links in the LAG bundle. The PDUs contain information about each link
and enable the LAG bundle to maintain them.
By default, Ethernet links do not exchange PDUs, which contain information about
the state of the link. You can configure Ethernet links to actively transmit PDUs, or
passively transmit them, sending out LACP PDUs only when it receives them from
another link. The transmitting link is known as the
Actor and the receiving link is
known as the Partner .
Higher-Level Protocols
After you configure the LAG bundle, you can route IP traffic over it, create a VLAN
over it, route PPPoE traffic over it, or route MPLS traffic over it.
Figure 20 on page 200 displays the interface stack for 802.3ad link aggregation.
Figure 20: Interface Stack for 802.3ad Link Aggregation
MPLS
OR
OR
PPPoE
IP VLAN
OR
LAG bundle
MAC MAC MAC MAC
802.3ad Link Agg regation Interf ace
g016437
Fast Ether net
interface
4/0
Fast Ether net
interface
4/2
Fast Ether net
interface
4/3
Fast Ether net
interface
4/5
For information about configuring higher-level protocols over VLANs, see “Configuring
VLAN and S-VLAN Subinterfaces” on page 169.
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802.3ad Link Aggregation for Ethernet Overview
JUNOSe 11.1.x Link Layer Configuration Guide