Cisco Nexus 5000 Series and Cisco Nexus 2000 Series Release Notes, for Cisco NX-OS Release 5.0(2)N1(1) and NX-OS Release 5.0(2)N2(1) OL-22747-02, December 2010)

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Cisco Nexus 5000 Series and Cisco Nexus 2000 Series Release Notes, for Cisco NX-OS Release 5.0(2)N1(1) and NX-OS Release 5.0(2)N2(1)
OL-22747-02
Limitations
Non-Edge Designated Forwarding Ports is required for an ISSU. For additional information, see
CSCtf51577. For information topologies that a nondisruptive upgrade is supported, refer 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 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 group 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
or downgrading between Cisco NX-OS Release 4.2(1)N1(1) and earlier releases, Cisco NX-OS
automatically converts the configuration to address this semantic change by adding or subtracting
38 to the MTU to address the Ethernet header size.
In a vPC configuration, the MTU per class needs to be consistent on both switches in the vPC
domain for the vPC peer-link to come up. When upgrading/downgrading a working vPC setup
between pre-4.2(1)N1(1) and 4.2(1)N1(1) releases, the MTU is adjusted to make sure that the MCT
peer-link always comes up.
However if you add a peer-link between two switches in a vPC domain that are identically
configured (MTU in particular) with one switch running Cisco NX-OS Release 4.2(1)N1(1) and
another switch running an earlier release, then the vPC peer-link does not come up because the MTU
is inconsistent between the two switches.
This is not an issue when upgrading or downgrading peer switches in a vPC domain; this is only an
issue when adding a peer-link between two switches running Cisco NX-OS Release 4.2(1)N1(1) and
earlier releases that were not previously in the same vPC domain.
To resolve this issue, upgrade downgrade one switch to match the version on the other switch and
reconfigure the MTU to be consistent on both sides. For details, see CSCtg27538.
• The channel-group configuration is not applied to the Cisco Nexus 2000 Series downlink interface
after downgrading to the Cisco NX-OS Release 4.1(3)N1(1) software. This issue occurs if the speed
1000 command is present under the context of the port channel. To workaround this issue,
reconfigure the channel-group command after the system comes up and reapply the configuration
from the saved configuration in the bootflash. For details, see CSCtc06276.
• When a private VLAN port is configured as a TX (egress) SPAN source, the traffic seen at the SPAN
destination port is marked with the VLAN of the ingressed frame. There is no workaround.