Juniper EX2200 Hardware Manual page 118

Network Interfaces for EX4300 Switches
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98
On an EX8200, EX6200, or QFX Series switch, ensure that the selected switch interface
is symmetrically routed before you enable unicast RPF. A symmetrically routed interface
is an interface that uses the same route in both directions between the source and the
destination. Do not enable unicast RPF on asymmetrically routed interfaces. An
asymmetrically routed interface uses different paths to send and receive packets
between the source and the destination.
On an EX3200, EX4200, or EX4300 switch, ensure that all switch interfaces are
symmetrically routed before you enable unicast RPF on an interface. When you enable
unicast RPF on any interface, it is enabled globally on all switch interfaces. Do not
enable unicast RPF on asymmetrically routed interfaces. An asymmetrically routed
interface uses different paths to send and receive packets between the source and
the destination.
To enable unicast RPF, configure it explicitly on a selected customer-edge interface:
[edit interfaces]
user@switch# set ge-1/0/10 unit 0 family inet
BEST PRACTICE:
is enabled globally on all switch interfaces, regardless of whether you
configure it explicitly on only one interface or only on some interfaces.
On EX3200, EX4200, and EX4300 switches, we recommend that you enable
unicast RPF explicitly on either all interfaces or only one interface. To avoid
possible confusion, do not enable it on only some interfaces:
Enabling unicast RPF explicitly on only one interface makes it easier if you
choose to disable it in the future because you must explicitly disable unicast
RPF on every interface on which you explicitly enabled it. If you explicitly
enable unicast RPF on two interfaces and you disable it on only one
interface, unicast RPF is still implicitly enabled globally on the switch. The
drawback of this approach is that the switch displays the flag that indicates
that unicast RPF is enabled only on interfaces on which unicast RPF is
explicitly enabled, so even though unicast RPF is enabled on all interfaces,
this status is not displayed.
Enabling unicast RPF explicitly on all interfaces makes it easier to know
whether unicast RPF is enabled on the switch because every interface
shows the correct status. (Only interfaces on which you explicitly enable
unicast RPF display the flag that indicates that unicast RPF is enabled.)
The drawback of this approach is that if you want to disable unicast RPF,
you must explicitly disable it on every interface. If unicast RPF is enabled
on any interface, it is implicitly enabled on all interfaces.
Example: Configuring Unicast RPF on an EX Series Switch
Verifying Unicast RPF Status on page 239
Disabling Unicast RPF (CLI Procedure) on page 99
rpf-check
On EX3200, EX4200, and EX4300 switches, unicast RPF
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