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
These messages are informational only, and result in no loss of functionality.
• If you configure Multiple Spanning Tree (MST) on a Cisco Nexus 5000 Series switch, we do not
recommend that you partition the network into a large number of regions.
• A downgrade from Cisco NX-OS Release 5.1(3)N1(1) to any 5.0(3)N1(x) image can cause the Cisco
Nexus 5000 Series switch to fail. For details, see CSCty92945.
• If you upgrade a vPC Peer switch from Cisco NX-OS Release 5.0(3)N2(1) to Cisco NX-OS
Release5.1(3)N2(1) and feature-set fabricpath is enabled on the upgraded switch, the vPC Peer-Link
enters STP Bridge Assurance Inconsistency which affects all VLANs except VLAN 1 and affects
traffic forwarding for vPC ports.
To avoid this issue, upgrade the peer switch that is running Cisco NX-OS Release 5.0(3)N2(1)
switch also to Cisco NX-OS Release 5.1(3)N2(1) or higher and then enable feature-set fabricpath
on the switch or switches. If you accidentally enable feature-set fabricpath in Cisco NX-OS Release
5.1(3)N2(1) when the peer vPC switch is running Cisco NX-OS Release 5.0(3)N2(1), disable the
feature-set fabricpath and the vPC will resume STP forwarding state for all VLANs.
• By design, vEth interfaces do not share the underlying behavior of a vPC port. As a result, a VLAN
does not get suspended when the peer switch suspends it. For example, when you shut a VLAN on
a primary switch, the VLAN continues to be up on the secondary switch when the vEth interface is
on a FEX. When the VLAN on the primary switch goes down, the VLAN on the vEth interface on
the primary is suspended, but the vEth on the secondary switch is up as it is an active VLAN on the
secondary switch.
• RBACL policy enforcement is performed on VLANs on which CTS enforcement is not configured.
This situation occurs when there is at least one VLAN in the switch where CTS is enforced. On a
VLAN where CTS is not enforced, RBACL policy lookup occurs for ingress packets and the packet
is denied or permitted according to the policies in the system. To work around this issue, make sure
that all VLANs on which SGT tagged packets ingress enforce CTS.
• The packet length in the IP GRE header of a packet exiting from the switch is not equal to the MTU
value configured in the ERSPAN source session. This is true for SPAN or ERSPAN. This situation
can occur whenever the MTU value that is configured in an ERSPAN or SPAN session is smaller
than the SPAN packet, such as when the packet is truncated. The IP GRE packet is truncated to a
value that differs by -2 to 10 bytes from the expected MTU.
• When you configure a Layer 3 interface as an ERSPAN source, and configure the ERSPAN
termination on a Catalyst 6000 switch or a Cisco Nexus 7000 Series switch, you cannot terminate
the Layer 3 interface ERSPAN source on the Cisco Nexus 7000 Series switch or the Catalyst 6000
switch. To work around this issue, configure VLAN 1 to 512 on the Cisco Nexus 7000 Series switch
or the Catalyst 6000 switch.
• Unknown Unicast packets in FabricPath ports are counted as Multicast packets in interface counters.
This issue occurs when unknown Unicast packets are sent and received with a reserved Multicast
address (that floods to a VLAN) in the outer FabricPath header, and the Cisco Nexus 5000 Series
switch increments the interface counter based on the outer FabricPath header. As a result, multicast
counters are incremented. In the case of a Cisco Nexus 7000 Series switch, Unicast counters are
incremented as they are based on an inner Ethernet header. There is no workaround for this issue.
• If you configure a speed of 1 G on a base or GEM port and then check for compatibility with a Cisco
NX-OS Release 5.0(2) image, no incompatibility is shown. However, because 1 G was not supported
in the Cisco NX-OS Release 5.0(2), an incompatibility should be shown. To work around this issue,
manually remove the 1 G configuration from the ports before downgrading to Cisco NX-OS Release
5.0(2) or an earlier release.
• In an emulated switch setup, inband keepalive does not work. The following steps are recommended
for peer keepalive over SVI when a switch is in FabricPath mode: