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4/07/2012

Cisco Flex Links vs. Juniper Redundant Trunk Group (RTG)

Hi,

Flex Links are much same as RTG (Redundant Trunk Group). It is mostly used when you want to avoid using Spanning Tree and on access switches connecting to two aggregation switches.
See a picture on page http://www.juniper.net/techpubs/en_US/junos12.1/topics/concept/cfm-redundant-trunk-groups-understanding.html

Requirements:
  • Juniper EX series switch with Junos 10.4 or later
  • Ports configured with family ethernet-switching
RTG ports could be "simple ports" like ge-0/0/0 or it could be also aggregated ingerfaces (ae0) with family ethernet-switching Primary and backup need not to be of same type. By setting aggregated interfaces "set interfaces ae0 aggregated-ethernet-options minimum-links X" you could specify when is aggregated interface treated like not working.


Go to configuration mode
cisco >configure terminal "Switch(conf)#
Juniper >configure "user@switch#"
Purpose IOS Junos
disable spanning tree on port Spanning tree is turned off automatically on flex links user@host# set protocols rstp interfaces ge-0/0/5 disable
user@host# set protocols rstp interfaces ge-0/0/6 disable
Set Flex Links / RTG Switch(conf)# interface gigabitethernet0/1
Switch(conf-if)# switchport backup interface gigabitethernet0/2
user@host#  set ethernet-switching-options redundant-trunk-group group rtg1 interface ge-0/0/5.0 primary
user@host# set ethernet-switching-options redundant-trunk-group group rtg1 interface ge-0/0/6.0
Configure preemption (optional) "preemption modes: forced, bandwidth, off. For preempion to work, set forced or bandwidth."
Switch(conf-if)# switchport backup interface gigabitethernet0/2 preemption mode [forced | bandwidth ]
Switch(conf-if)# switchport backup interface gigabitethernet0/2 preemption delay 60
"Change the length of time (from the default 120 seconds) that a re-enabled primary link waits to take over for an active secondary link."
user@host# set redundant-trunk-group group tg1 preempt-cutover-timer 60
Show Flex Link/RTG status Switch(conf-if)# exit
Switch(conf)# exit
Switch# show interface switchport backup
Switch# show interface switchport backup detail
user@host# run show redundant-trunk-group
Save configuration / apply and save configuration Switch# copy running-config startup-config user@host# commit

This contribution is also listed in forums.juniper.net - IOS to Junos (I2J) Tips Contest
Flex Links vs RTG