Troubleshooting Unicast Rpf; Legitimate Packets Are Discarded; Ex4200 Switches - Juniper JUNOS OS 10.3 - SOFTWARE Manual

Complete Software Guide for Junos

Troubleshooting Unicast RPF

Legitimate Packets Are Discarded

Problem
Solution
Related
Documentation
Troubleshooting Uplink Module Installation or Replacement on EX3200 and EX4200
Switches
1178
®
OS for EX Series Ethernet Switches, Release 10.3
Troubleshooting issues for unicast reverse-path forwarding (RPF) on EX Series switches
include:
Legitimate Packets Are Discarded on page 1178
1.
The switch filters valid packets from legitimate sources, which results in the switch's
discarding packets that should be forwarded.
The interface or interfaces on which legitimate packets are discarded are asymmetrically
routed interfaces. An asymmetrically routed interface uses different paths to send and
receive packets between the source and the destination, so the interface that receives
a packet is not the same interface the switch uses to reply to the packet's source.
Unicast RPF works properly only on symmetrically routed interfaces. A symmetrically
routed interface is an interface that uses the same route in both directions between the
source and the destination. Unicast RPF filters packets by checking the forwarding table
for the best return path to the source of an incoming packet. If the best return path uses
the same interface as the interface that received the packet, the switch forwards the
packet. If the best return path uses a different interface than the interface that received
the packet, the switch discards the packet.
NOTE: On EX3200 and EX4200 switches, unicast RPF works properly only
if all switch interfaces—including aggregated Ethernet interfaces (also referred
to as link aggregation groups or LAGs) and routed VLAN interfaces (RVIs)—are
symmetrically routed, because unicast RPF is enabled globally on all switch
interfaces.
Verifying Unicast RPF Status on page 1171
Understanding Unicast RPF for EX Series Switches on page 1105
This topic provides troubleshooting information for specific problems related to uplink
module ports on EX3200 and EX4200 switches.
Virtual Chassis port (VCP) connection does not work on page 1179
1.
One of the last four network ports on an EX3200 switch with an SFP or SFP+ uplink
2.
module installed is disabled on page 1179
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