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
• Starting with Cisco NX-OS Release 4.2(1)N2(1), LACP fast timers are supported. If you downgrade
to an earlier release that does not support this feature, entering the install all command displays the
following warning:
"Configuration not supported - Lacp fast rate is enabled",
"Use \"lacp rate normal\" on those interfaces"
Before downgrading to an earlier release, change the LACP rate to normal. If you ignore the warning
and force the installation, then it is possible that the leftover LACP rate fast configuration would
still be active with previous releases of software but the behavior would be unpredictable and link
flap might occur. We recommend that you change the LACP rate setting to normal. For details, see
CSCth93787.
• When an FC SPAN destination port is changed from SD to F mode and back to SD mode on a NPV
switch, the port goes into an error-disabled state. Perform a shut/no-shut after the mode change
recovers the port. This issue occurs only in NPV mode. For details, see CSCtf87701.
• If you configure a Cisco Nexus 2248TP port to 100 Mbps instead of autonegotiation, then
autonegotiation does not occur, which is the expected behavior. Both sides of the link should be
configured to both hardwired speed or both autonegotiate.
no speed—Autonegotiates and advertises all speeds (only full duplex).
speed 1000—Autonegotiates only for a 802.3x pause.
speed 100—Does not autonegotiate; pause cannot be advertised. The peer must be set to not
autonegotiate and fix at 100 Mbps (similar to the N2248TP)
For details, see CSCte81998.
• Given the implementation of a single CPU ISSU, the STP root on the PVST region with switches on
an MST region is not supported. The PVST simulation on the boundary ports go into a PVST SIM
inconsistent blocked state that breaks the STP active path. To work around this issue, move all STP
roots to the MST region. However, the workaround causes a nondisruptive ISSU to fail because
non-edge designated forwarding ports are not allowed for an ISSU. For additional information, see
CSCtf51577. For information topologies that a nondisruptive upgrade is supported, see to the Cisco
Nexus 5000 Series NX-OS Upgrade and Downgrade Guide.
• IGMP queries sent in CSCtf94558 are group-specific queries that are sent with the destination
IP/MAC address as the group's address.
GS queries are sent for IP address: 224.1.14.1 to 224.1.14.100 [0100.5E01.0E01 to
0100.5E01.0E64]
These are not link-local addresses. By default, they are not flooded by the hardware into the VLAN.
They are sent only to the ports that have joined this group.
This is expected behavior during an ISSU.
In another scenario, the IGMP global queries [dest IP 224.0.0.1] get flooded correctly in the VLAN.
Group-specific queries are not forwarded to ports other than the one that joined the group during
ISSU. The reason to forward group-specific queries toward hosts is to avoid having them leave the
group. However, if a port has not joined the group, then this is not an issue. If there is an interface
that has joined the group, then the queries are expected to make it to the host. While the behavior is
different when ISSU is not occurring, it is sufficient and works as expected and there is no impact
to traffic. For details, see CSCtf94558.
• The meaning of an MTU configuration has changed in Cisco NX-OS Release 4.2(1)N1(1) and
earlier releases. In releases earlier than Cisco NX-OS Release 4.2(1)N1(1), the configured MTU
included the Ethernet payload and Ethernet headers. In Cisco NX-OS Release 4.2(1)N1(1), the
configured MTU includes only the Ethernet payload and not the Ethernet headers. When upgrading