Understanding Redundant Trunk Links On Ex Series Switches - Juniper JUNOS OS 10.4 - FOR EX REV 1 Manual

Complete Software Guide for Junos

Understanding Redundant Trunk Links on EX Series Switches

1512
®
OS for EX Series Ethernet Switches, Release 10.4
In a typical enterprise network comprised of distribution and access layers, a redundant
trunk link provides a simple solution for network recovery when a trunk port goes down.
Traffic is routed to another trunk port, keeping network convergence time to a minimum.
You can configure a maximum of 16 redundant trunk groups on a standalone switch or
on a Virtual Chassis.
To configure a redundant trunk link, create a redundant trunk group. The redundant trunk
group is configured on the access switch, and contains two links: a primary or active link,
and a secondary link. If the active link fails, the secondary link automatically starts
forwarding data traffic without waiting for normal STP convergence.
Data traffic is forwarded only on the active link. Data Traffic on the secondary link is
dropped and shown as dropped packets when you issue the operational mode command
show interfaces xe- interface-name extensive
While data traffic is blocked on the secondary link, Layer 2 control traffic is still permitted.
For example, an LLDP session can be run between two Juniper Networks EX Series
Ethernet Switches on the secondary link.
STP is enabled by default on EX Series switches to create a loop-free topology. When
trunk links are placed in a redundant group, they cannot be part of an STP topology. The
Juniper Networks Junos operating system (Junos OS) for EX Series switches does not
allow an interface to be in a redundant trunk group and in an STP topology at the same
time. However, STP can continue operating in other parts of the network. For example,
STP may continue operating between the distribution switches and linking them to the
enterprise core.
Figure 36 on page 1513 shows three switches in a basic topology for redundant trunk links.
Switch 1 and Switch 2 make up the distribution layer, and Switch 3 makes up the access
layer. Switch 3 is connected to the distribution layer through trunk ports
1) and ge-0/0/10.0 (Link 2). Link 1 and Link 2 are in a redundant trunk group called
Link 1 is designated as the primary link. Traffic flows between Switch 3 in the access layer
and Switch 1 in the distribution layer through Link 1. While Link 1 is active, Link 2 blocks
traffic.
.
Copyright © 2010, Juniper Networks, Inc.
(Link
ge-0/0/9.0
group1 .