Administrator Guide

206 Stacking
forwarding table entries. If the cleanup leaves a route without any next hops,
the route is deleted. The forwarding plane only selects ECMP next hops on
surviving units. For this reason, try to distribute links providing ECMP paths
across multiple stack units.
Why is Stacking Needed?
Stacking increases port count without requiring additional configuration. If
you have multiple Dell Networking N-Series switches, stacking them helps
make management of the switches easier because you configure the stack as a
single unit and do not need to configure individual switches.
Default Stacking Values
Stacking is always enabled on Dell Networking N-Series switches.
On the Dell Networking N1500/N4000 Series switches, by default, the 10G
SFP+ ports are in Ethernet mode and must be configured to be used as
stacking ports. Ports that are configured in stacking mode show as “detached”
in the output of the show interfaces status command.
Configuring an Ethernet port as a stacking port changes the default
configuration of the port. The port stacking configuration does not show in
the running-config. To determine the stacking configuration of a port, use the
show switch stack-ports command. On the Dell Networking N2000/N3000
Series switches, there are two fixed stacking ports in the rear of the switch.
Stacking on Ethernet ports is not supported. The fixed stacking ports show as
TwentygigabitStacking and are abbreviated Tw.
NSF is enabled by default. NSF can be disabled to redirect the CPU resources
consumed by data checkpointing; however, this is ill-advised, as
checkpointing consumes almost no switch resources. Checkpointing only
occurs when a backup unit is elected, so there is no need to disable the NSF
feature on a standalone switch. When a new unit is added to the stack, the
new unit is given the configuration of the stack, including the NSF setting.
OSPF implements a separate graceful restart control that enables NSF for
OSPF. OSPF graceful restart is not enabled by default.
NOTE: N1500 10G SFP+ ports may only be configured as stacking in pairs.