Figure 1: ERSPAN Configuration
Multiple ERSPAN Sessions
You can define up to eight unidirectional ERSPAN source or SPAN sessions, or four bidirectional ERSPAN
source or SPAN sessions at one time. You can shut down any unused ERSPAN sessions.
For information about shutting down ERSPAN sessions, see Shutting Down or Activating an ERSPAN
Session, on page 157.
ERSPAN Marker Packet
The type III ERSPAN header carries a hardware generated 32-bit timestamp. This timestamp field wraps
periodically. When the switch is set to 1 ns granularity, this field wraps every 4.29 seconds. Such a wrap time
makes it difficult to interpret the real value of the timestamp.
To recover the real value of the ERSPAN timestamp, Cisco NX-OS Release 6.0(2)A4(1) introduces a periodical
marker packet to carry the original UTC timestamp information and provide a reference for the ERSPAN
timestamp. The marker packet is sent out in 1-second intervals. Therefore, the destination site can detect the
32-bit wrap by checking the difference between the timestamp of the reference packet and the packet order.
High Availability
The ERSPAN feature supports stateless and stateful restarts. After a reboot or supervisor switchover, the
running configuration is applied.
Licensing Requirements for ERSPAN
The following table shows the licensing requirements for this feature:
Cisco Nexus 3548 Switch NX-OS System Management Configuration Guide, Release 7.x
149
Configuring ERSPAN
Multiple ERSPAN Sessions
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