Cisco DCIT 300-615 flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

vPC type-1 vs type-2

Type-1 parameters (MTU, STP mode, VXLAN source, etc.) must match on both vPC peers or vPC stays down. Type-2 parameters (e.g., VLAN lists, allowed VLANs) only generate a warning and vPC stays up.

vPC peer-keepalive purpose

Heartbeat over a separate L3 path (management or dedicated link) that lets peers detect each other's liveness even when the peer link fails, preventing split-brain and dual-active forwarding.

vPC peer link role

Carries control traffic (CFS, STP BPDUs, ARP sync) and orphan/data traffic when the peer is reachable; if it fails while keepalive is up, the secondary suspends its vPC member ports.

vPC consistency-parameters command

'show vpc consistency-parameters global' and 'interface <if>' list per-parameter local values on both peers and mark type-1 (mandatory) versus type-2 (advisory) mismatches.

Suspended port-channel member

Member shows 's' or 'I' in 'show port-channel summary'; caused by speed/duplex/MTU mismatch, LACP mode mismatch, VLAN mismatch, or vPC type-1 mismatch. Check 'show port-channel compatibility-parameters'.

CRC and input errors

Rising FCS/CRC counters on an interface indicate Layer 1 problems: bad cable, dirty connector, failing SFP, or duplex mismatch. Confirm with 'show interface counters errors' and transceiver DOM levels.

NVE peer state verification

'show nve peers' should show peer state Up for every VTEP; 'show nve vni' shows VNI state and mode (CP/DP). Down peers usually indicate underlay reachability or BGP EVPN session failure.

EVPN route types

Type-2 advertises MAC/IP; Type-3 advertises inclusive multicast (BUM); Type-5 advertises IP prefix; Type-1 Ethernet auto-discovery for multihoming; Type-4 Ethernet segment. Verify with 'show bgp l2vpn evpn route-type'.

VXLAN underlay requirements

Underlay must provide IP reachability between VTEP loopbacks, MTU sized for 50-byte VXLAN overhead, and PIM/ingress-replication for BUM traffic. Verify with 'show ip route' and 'show nve interface nve1'.

FabricPath ISIS adjacency

'show fabricpath isis adjacency' should show all spine/leaf neighbors Up. Down adjacencies indicate link, MTU, or ISIS authentication mismatch; 'show fabricpath route' confirms switch-id reachability.

STP root verification

'show spanning-tree vlan <id>' shows root bridge ID, local bridge ID, and port roles. If the expected root is not elected, check bridge priority, extended system ID, and vPC/STP domain consistency.

Control-plane CPU diagnosis

'show processes cpu sort | head' and 'show processes cpu history' identify the top consumers. Sustained high CPU from a single process (e.g., BGP,ARP) suggests a loop, flapping neighbor, or misbehaving feature.

Logging severity levels

Syslog severities 0-7: 0 emergencies, 1 alerts, 2 critical, 3 errors, 4 warnings, 5 notifications, 6 informational, 7 debugging. 'logging level <feature> <n>' sends messages at or below that severity.

show tech-support collection

Bundle of show outputs (interfaces, routes, hardware, logs) used for TAC cases. On NX-OS it writes to bootflash by default; collect before rebooting or clearing counters.

Port-channel LACP neighbor check

'show lacp neighbor' shows each member's partner system ID, port state, and flags. Mismatched partner or 'Suspended' state indicates cabling to the wrong peer or LACP mode mismatch.

Configuration rollback

'configure replace <file>' or 'rollback running-config checkpoint <name>' restores a prior state. Verify with 'show archive config differences' to preview deltas before committing.

Transceiver DOM diagnostics

'show interface <if> transceiver details' shows Rx/Tx power in dBm. Rx power below spec or 'N/A' indicates a failed SFP, dirty fiber, or wrong optics type; check against vendor thresholds.

show module status

Lists supervisor and line card slots with status (ok, powered-up, failure). A 'failure' or 'powered-down' state indicates hardware or slot power issue; check 'show environment' for PSU/thermal faults.

vPC orphan port

A port in a vPC VLAN that is not a vPC member and is up on only one peer. Traffic reaches it via the peer link; if the peer link fails, orphan ports on the secondary are suspended.

BGP EVPN neighbor state

'show bgp l2vpn evpn summary' shows peer state and prefix counts. Idle/Active indicates TCP/port 179 or reachability issue; Established but no routes indicates route-target or address-family mismatch.

Interface MTU mismatch

MTU mismatch on a trunk or vPC member causes large frames to drop silently. Verify with 'show interface' MTU field and 'show run interface'; VXLAN underlay needs MTU >= 1550 typically.

ARP and MAC table verification

'show ip arp vrf <name>' and 'show mac address-table' confirm learning. Missing entries point to VLAN/VRF misconfiguration, STP blocking, or vPC/EVPN learning failure.

Interface flap detection

'show interface <if>' shows 'last link flapped' and 'reset counters interface' clears stats. Frequent flaps indicate cabling, SFP, or negotiation issues; correlate with 'show logging logfile'.

show environment output

Displays fan tray, power supply, and temperature sensor status. Any 'failure' or 'not ok' entry indicates a hardware or cooling issue that can cause line card resets or shutdowns.

VRF route table check

'show ip route vrf <name>' and 'show ip route vrf <name> summary' confirm per-tenant routing. Missing routes indicate VRF-to-global leak misconfig, missing 'ip route' statements, or BGP/OSPF not redistributing.

NVE VNI mode CP vs DP

'show nve vni' mode CP (control-plane, via BGP EVPN) or DP (data-plane, static/flood-and-learn). Wrong mode prevents EVPN MAC learning; verify 'vni <id> mcast-group' or 'l2' config under nve.

LLDP topology mapping

'show lldp neighbors' and 'show cdp neighbors detail' reveal adjacent device, port, and management IP. Useful to confirm cabling matches the intended topology before changing vPC or fabric config.

Interface counters errors

'show interface counters errors' lists FCS, runts, giants, input/output errors per port. Non-zero sustained values indicate physical layer faults or duplex/MTU mismatch; clear with 'clear counters interface'.

vPC role and priority

'show vpc role' shows primary/secondary and operational priority. Lower priority number wins; if both peers show primary, peer link/keepalive is broken and split-brain may be active.

Process memory leak check

'show processes memory sort | head' identifies top consumers; compare over time or after reload. Steady growth in a single process suggests a leak; capture 'show tech-support' before restart.

show running-config diff

Compares running config against a prior snapshot or checkpoint, showing added and removed lines. Use to validate that a change applied as intended and no unintended deltas exist.

VLAN allowed list mismatch

On a trunk, 'switchport trunk allowed vlan' must include the VLANs carried. Missing VLANs cause silent drops; verify on both ends and on vPC peers with 'show interfaces trunk'.