Cisco Nexus 7000 Series Configuration Manual page 363

Configuring ERSPAN
• For F2 Series and F2e Series modules, egress ERSPAN packets of all traffic that ingresses on Layer 2
ports (including edge-to-edge traffic) have a 16-byte MAC-in-MAC header at the ERSPAN destination.
• While setting IP TTL in the ERSPAN header,
• For MTU truncation on M2 Series modules, the truncated length of ERSPAN packets is rounded down
to the nearest multiplier of 16 bytes. For example, with an MTU configuration value of 65 to 79, packets
are truncated to 64 bytes.
• For certain rate limit and packet size values on F2 Series modules, F2e Series modules, M2 Series
modules, and Supervisor 2, the ERSPAN packet rate is less than the configured value because of the
internal accounting of packet sizes and internal headers.
• ERSPAN sampling is supported only on F2 Series and F2e Series modules. It is not supported on M
Series modules.
• Multicast best effort mode applies only to M1 Series modules.
• Beginning with Cisco NX-OS Release 6.1, ERSPAN source sessions are supported on Supervisor 2, but
ERSPAN ACL sessions are not.
• ERSPAN Type III source is supported only on F2 Series, F2e Series, and M2 Series modules.
• ERSPAN Type III termination is supported only on M2 Series modules. That is, Type III ERSPAN
packets are decapsulated only when they reach their destination through M2 Series modules.
• Beginning with Cisco NX-OS Release 6.2(2), ERSPAN packets ingressing the destination switch on F2
Series or F2e Series modules can be terminated. IPv4 termination is supported but not IPv6 termination.
F2 Series module termination on VDC virtual routing and forwarding (VRF) instances is not supported.
• Supervisor 2 supports ERSPAN Type II and ERSPAN Type III for inband ports, but timestamps are not
synchronized with the Precision Time Protocol (PTP) master timers.
• 1588 granularity mode is not supported in Cisco NX-OS Release 6.1 and is rejected if selected.
• M2 Series modules support 100 microseconds (ms), 100 nanoseconds (ns), and ns granularity. F2 Series
and F2e Series modules support only 100 ms and 100 ns granularity.
• When ERSPAN traffic is terminated on M2 Series modules, drops can occur at higher rates because all
ERSPAN traffic for one session converges into one forwarding instance.
• If the global granularity configuration is not supported for a particular module, that module reverts to
100-ms granularity. For example, if granularity is set to ns, all M2 Series modules will enable ns
granularities, and all F2 Series and F2e Series modules will internally enable and send packets with the
100-ms timestamp. Use the show monitor session command to display the supported and unsupported
granularities for each module.
• F2 Series and F2e Series modules do not use the access control list (ACL) complex for ERSPAN Type
III ACLs, so an ACL filter cannot be applied to F2 Series and F2e Series module traffic. However, for
M2 Series modules, it is possible to encapsulate the packets using the Type III header after applying an
ACL.
◦ In M-series LC, after ERSPAN encapsulation / de-capsulation, the packets are sent to EARL for
recirculating and hence, the TTL is decremented by EARL.
◦ In F2/F2e, there are no overheads of recirculating and hence, there is digression from the actual
behavior of TTL decrements.
◦ F1 series does not support ERSPAN.
Cisco Nexus 7000 Series NX-OS System Management Configuration Guide
Guidelines and Limitations for ERSPAN
335