Cisco Nexus 5000 Series and Cisco Nexus 2000 Series Release Notes,Cisco NX-OS Release 5.1(3)N2(1a) and NX-OS Release 5.1(3)N2(1)

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Cisco Nexus 5000 Series and Cisco Nexus 2000 Series Release Notes, Cisco NX-OS Release 5.1(3)N2(1a) and NX-OS Release 5.1(3)N2(1)
OL-26652-02
Limitations
• Spanned FCoE frames do not preserve original SMAC and DMAC fields. The Ethernet header gets
modified as the frame is spanned to the destination. The modified header fields are displayed when
monitored on the SPAN destination.
• The CoS value in spanned FCoE frames on the Ethernet SPAN destination port does not match with
the CoS value in the SPAN FCoE source frame. The CoS value on the captured SPAN FCoE frame
should be ignored.
• The class-fcoe cannot be removed even if Fibre Channel is not enabled on a switch.
• If a port drains traffic at a rate less than 100 Kbps, it is error-disabled in 10 seconds to avoid buffer
exhaustion. However, if the drain rate is larger than 100 Kbps, the port may not be consistently
error-disabled within 10 seconds which exhaust ingress buffers and discard frames. Use the shut
command to disable the slow-draining port.
• The multicast storm control functionality in the Cisco Nexus 5000 Series does not distinguish
between IP, non-IP, registered, or unregistered multicast traffic. All multicast traffic is subject to a
single-multicast storm control policer when configured.
IGMP Snooping Limitation
On the Cisco Nexus 5010 switch and the Cisco Nexus 5020 switch with a Cisco Nexus 2000 Series
Fabric Extender (FEX) installed, unregistered IP multicast packets on one VLAN are forwarded to other
VLANs where IGMP snooping is disabled. We recommend that you do not disable IGMP snooping on
the Cisco Nexus 5010 switch and the Cisco Nexus 5020 switch. A static IGMP join can be configured
for devices intended to receive IP multicast traffic but not to send IGMP join requests. This limitation
applies to the Cisco Nexus 5010 switch and the Cisco Nexus 5020 switch only.
SPAN Limitations on Fabric Extender Ports
The SPAN limitations on Fabric Extender ports are as follows:
• On a Cisco Nexus 5000 Series switch, if the SPAN source is a FEX port, the frames will always be
tagged when leaving the SPAN destination.
• On a Cisco Nexus 5010 switch or a Nexus 5020 switch, if the SPAN source is an access port on a
switch port or FEX port, the spanned frames at the SPAN destination will be tagged.
• On a Cisco Nexus 5500 Platform switch, if the SPAN source is on an access port on the switch port,
the frames will not be tagged when leaving the SPAN destination.
• Ports on a FEX can be configured as a tx-source in one session only.
If two ports on the same FEX are enabled to be tx-source, the ports need to be in the same session.
If you configure a FEX port as a tx-source and another port belonging to the same FEX is already
configured as a tx-source on a different SPAN session, an error is displayed on the CLI.
In the following example, Interface Ethernet100/1/1 on a FEX 100 is already configured as a
tx-source on SPAN session-1:
swor28(config-monitor)# show running-config monitor
version 4.0(1a)N2(1)
monitor session 1
source interface Ethernet100/1/1 tx
destination interface Ethernet1/37
no shut