FTOS Configuration Guide for the C-Series - Force10 Networks

Configuring Redundant Pairs
Configuring Redundant Pairs is supported only on platform e
Networks that employ switches that do not support Spanning Tree (STP)—for example, networks with
Digital Subscriber Line Access Mutiplexers (DSLAM)—cannot have redundant links between switches
because they create switching loops (Figure 115). The Redundant Pairs feature enables you to create
redundant links in networks that do not use STP by configuring backup interfaces for the interfaces on
either side of the primary link.
Note: For details on STP, see Chapter 19, Spanning Tree Protocol, on page 385.
Assign a backup interface to an interface using the command switchport backup. The backup interface
remains in down state until the primary fails, at which point it transitions to up state. If the primary
interface fails, and later comes up, it becomes the backup interface for the redundant pair. FTOS supports
Gigabit and 10-Gigabit interfaces as backup interfaces.
You must apply all other configurations to each interface in the redundant pair such that their
configurations are identical, so that transition to the backup interface in the event of a failure is transparent
to rest of the network.
Figure 115 Configuring Redundant Layer 2 Pairs without Spanning Tree
Force10(conf-if-gi-3/41)#switchport
Force10(conf-if-gi-3/41)#switchport backup gi 3/42
Force10(conf-if-gi-3/41)#no shutdown
Force10(conf-if-gi-3/42)#switchport
Force10(conf-if-gi-3/42)#no shutdown
Redundant links create a switching loop.
Without STP broadcast storms occurs.
Use backup interfaces to create redundant
links in networks without STP
R3 R4
3/41 4/31
Backup Link
Force10(conf-if-gi-4/31)#switchport
Force10(conf-if-gi-4/31)#no shutdown
Force10(conf-if-gi-4/32)#switchport
Force10(conf-if-gi-4/32)#no shutdown
Important Points about Configuring Redundant Pairs
• You may not configure any interface to be a backup for more than one interface, no interface can have
more than one backup, and a backup interface may not have a backup interface.
• Neither the active nor the backup interface may be a member of a LAG.
• The active and standby do not have to be of the same type (1G, 10G, etc).
3/42
• You may not enable any Layer 2 protocol on any interface of a redundant pair or to ports connected to
them.
206 Layer 2
4/32
fnC0067mp