300-615 DCIT: Troubleshooting Cisco Data Center InfrastructureDemo

Cisco Nexus 7000 OTV supports selective unicast flooding with the otv flood mac mac-address vlan vlan-id command. It configures flooding for the specified destination MAC when the OTV MAC route is unavailable, such as after MAC aging. Cisco Nexus 7000 Series NX-OS OTV Configuration Guide—Configuring Advanced OTV Features

An OTV-edge Layer 3 VACL blocks HSRP control packets from crossing sites, and a Layer 2 MAC list prevents the HSRP virtual MAC from being advertised or used across the overlay. This localizes first-hop gateway behavior and keeps same-site traffic from taking an unnecessary OTV path.

Unicast RPF checks ingress packets against the forwarding information base to verify that the source address has a valid reverse path. Packets with forged or unverifiable source IP addresses are dropped, mitigating spoofed-source attacks.

A clean-reloaded leaf can receive stale infrastructure fabric parameters through LLDP from a switch that has not yet been cleaned. Those mismatched parameters prevent the leaf from registering or appearing in fabric membership. Cisco documents that all leaf switches must be clean rebooted simultaneously when infrastructure parameters change; otherwise a clean-reloaded leaf can learn the old infrastructure VLAN and fail to register with the APIC.

Port-security database activation can be rejected when entries are missing from, or conflict between, the configuration database and the active database. Comparing those databases reveals the conflicting or missing entries that caused the rejection.

An unresponsive Cisco UCS I/O Module during a firmware upgrade is recovered by issuing a reset from the peer I/O Module. Cisco documents this specifically as the IOM firmware-upgrade recovery procedure; Auto Install recovery applies to fabric-interconnect failures.

During an infrastructure firmware upgrade, Cisco UCS Manager automatically creates a full-state backup. The Equipment FSM page exposes the InternalBackup stage that performs the configuration backup, and the Admin page exposes the PollInternalBackup stage that waits for the backup to complete. A successful backup is retained as the latest bkp.timestamp.tgz file in /workspace/backup on both fabric interconnects.

Cisco ACI requires all virtual machines to be detached from an APIC-created VMware port group before the associated port group can be deleted. Reassigning the virtual machines in EPG-1 to different port groups removes the attachment that blocks deletion.

NPV automatically chooses an available NP uplink when a server interface initially logs in. A newly operational uplink is eligible for subsequent connections, but existing connections are not automatically redistributed unless disruptive load balancing is enabled.

An EEM policy that matches a CLI command must include an event-default action to permit the matched command to execute and its normal event processing to continue. The required addition is an action such as action 2.0 event-default.

VXLAN EVPN vPC peers use unique primary IP addresses for the NVE source loopback while sharing the same secondary anycast VTEP IP address. They must also maintain a consistent VNI-to-multicast-group mapping. Aligning the VNI multicast-group mapping and ensuring that the primary addresses differ resolves those Type-1 consistency violations.

An 8-Gb Fibre Channel SFP is valid only in a unified port configured for Fibre Channel. When the port is configured as Ethernet, Cisco UCS rejects the FC optic during SFP validation. Cisco documents that unified ports can carry either Ethernet or Fibre Channel traffic, and that the 8-Gb FC SFP is for FC-configured unified ports.

All routers providing one HSRP virtual gateway must be configured as members of the same HSRP group. That shared group supplies the common virtual IP and MAC address and allows active/standby election. HSRP group 26 is within the HSRP version 1 group-number range, so HSRP version 2 is unnecessary. Cisco documents that HSRP provides a virtual IP and MAC shared by the devices in an HSRP group.

An Ethernet interface bound to a virtual Fibre Channel (vFC) interface must operate as a trunk port. The shown interface is configured as an access port, so configuring it as a trunk satisfies the required interface mode. The FCoE VLAN mapped to the vFC VSAN must also be allowed on that trunk and must not be its native VLAN.

DCBX uses a sequence-based Control Sub-TLV acknowledgement exchange between the switch and the host/CNA. The interface is error-disabled after the switch fails to receive the expected acknowledgement from the host for 100 PDUs.

HSRP peers exchange multicast hello packets over the shared Layer 2 VLAN. If VLAN 100 is not permitted between the switches, neither switch receives the other’s hello packets; each therefore regards itself as active and lists the standby router as unknown. Allowing VLAN 100 between the switches restores HSRP peer communication and permits the priority election to select one active router.

For an LACP port channel connected to a non-Cisco Nexus peer, LACP graceful convergence can delay port-down handling and cause traffic from the peer to be lost. Disabling LACP graceful convergence provides the required interoperability behavior.

OSPF validates the interface MTU advertised in Database Description packets during adjacency establishment. A received value larger than the local interface can accept prevents the adjacency from forming. Disabling the OSPF MTU check allows the neighbors to complete the adjacency despite their differing MTU values.

For a global vNIC redundancy template pair used in a local Cisco UCS Manager service profile, the primary and secondary templates cannot be assigned at the same time. Assign the primary vNIC template and set the peer name for the second vNIC before assigning the secondary template manually.

EVPN route types 1 through 5 carry the standard EVPN control-plane information: Ethernet Auto-Discovery, MAC/IP Advertisement, Inclusive Multicast Ethernet Tag, Ethernet Segment, and IP Prefix routes. Route types 0 and 9 through 16 are not part of this standard set.

In a VXLAN vPC deployment, the designated forwarder installs the multicast encapsulation route, and a single elected peer installs the decapsulation multicast route. Sw1 has the source-specific multicast entry with Ethernet2/2 in its outgoing-interface list, whereas Sw2 has no outgoing interface for that entry; therefore, Sw1 performs VXLAN multicast encapsulation and decapsulation for the associated VNIs.

Cisco ACI discovery begins with an APIC directly connected to a leaf switch. Once that leaf is registered, the APIC discovers the spine switches connected to it, then the leaf switches connected to those spines. The ACI leaf-spine fabric topology uses APIC-to-leaf connections and leaf-to-spine fabric links; spine-to-spine and APIC-to-spine connections are not part of this topology.

HSRP version 2 does not interoperate with HSRP version 1. Nexus7K-1 is configured for version 2, while Nexus7K-2 defaults to version 1 when no version is configured; therefore, Nexus7K-2 must be configured for HSRP version 2. The two interface addresses already share the 10.35.164.0/25 subnet.

A leaf moved from another ACI fabric can retain the previous fabric configuration and fabric name, which creates a fabric-name mismatch and causes APIC to disable or show the node as inactive. A clean reload erases the switch configuration so it can receive the current fabric configuration from APIC.