Cisco Nexus 7000 Series Configuration Manual page 362

Guidelines and Limitations for ERSPAN
• You can enable ERSPAN for a source port before it becomes operationally active. For Layer 2 ports,
traffic flooded to the VLANs that contain these ports are captured even when the link is not connected
for the ports.
• For VLAN ERSPAN sessions with both ingress and egress configured, two packets (one from ingress
and one from egress) are forwarded from the destination port if the packets get switched on the same
VLAN.
• You can monitor the inband interface only from the default VDC. Inband traffic from all VDCs is
monitored.
• A FabricPath core port is not supported as an ERSPAN destination when an F2 Series or F2e Series
module is present in a VDC. However, a FabricPath core port can be configured as an ERSPAN source
interface.
• When using ERSPAN sessions on F2 Series or F2e Series modules, ensure that the total amount of
source traffic in a given session is less than or equal to the capacity of the ERSPAN destination interface
or port channel for that session. If the ERSPAN source traffic exceeds the capacity of the ERSPAN
destination, packet drops might occur on the ERSPAN source interfaces.
• Beginning with Cisco NX-OS Release 5.2, you can configure the Cisco Nexus 2000 Series Fabric
Extender (FEX) interfaces and the fabric port channels connected to the Cisco Nexus 2000 Series Fabric
Extender as ERSPAN sources. However, you cannot configure them as ERSPAN destinations.
Note
• You can span Fabric port channels on F2 Series and F2e Series modules.
• VLANs that contain FEX interfaces can be an ERSPAN source, but the ingress traffic through the F2
Series or F2e Series module-based FEX ports cannot be captured.
• Layer 3 multicast egress packets cannot be spanned on F2 Series or F2e Series modules.
• ERSPAN is supported on Fabric Extender interfaces in Layer 2 access mode, Layer 2 trunk mode, and
Layer 3 mode. Layer 3 subinterfaces are not supported.
• For ERSPAN sessions, the recommended MTU size is 144 bytes or greater because MTU truncation
occurs after the packets are encapsulated.
• The rate limit percentage of an ERSPAN session is based on 10G, 40G, and 100G for the respective
modules (that is, 1 percent corresponds to 0.1G, 0.4G, or 1G respectively), and the value is applied per
every forwarding engine instance.
• MTU truncation and the ERSPAN source rate limit are supported only on F2 Series, F2e Series, and
M2 Series modules and Supervisor 2. They are not supported on M1 Series modules.
• For F2 Series and F2e Series modules, spanned FabricPath (core) packets have a 16-byte core header
at the ERSPAN destination, and ingress FEX packets spanned through the fabric port channel have a
6-byte Vntag header at the ERSPAN destination. In addition, when trunk ports are used as the ERSPAN
destination, the spanned packets have a 4-byte VLAN tag.
Cisco Nexus 7000 Series NX-OS System Management Configuration Guide
334
ERSPAN on Fabric Extender interfaces and fabric port channels is supported on the
M1 Series and M2 Series modules. ERSPAN runs on the Cisco Nexus 7000 Series
device, not on the Fabric Extender. F2 Series and F2e Series modules support FEX, but
they do not support FEX ERSPAN. Therefore, the FEX interfaces that are connected
through the F2 Series and F2e Series modules cannot be made ERSPAN sources.
Configuring ERSPAN