Examkin

Soru

Zorluk: KolayTroubleshooting VLAN, Trunking, and Switching Issues

Match each switching troubleshooting symptom or log message on the left with its underlying root cause on the right.

  • Switch log continuously displays '%CDP-4-NATIVE_VLAN_MISMATCH' on trunk link interface Gig0/1.The native VLAN ID configured on local interface Gig0/1 does not match the native VLAN ID on the remote switch interface.
  • Workstation connected to a switch port experiences degraded performance with high counts of late collisions.Operating in a duplex mismatch state where one end is configured for full-duplex and the other for auto-negotiation (half-duplex).
  • Traffic for VLAN 20 fails to pass across an active 802.1Q trunk, while VLAN 10 traffic passes successfully.VLAN 20 is omitted from the allowed VLAN list configured on the trunk interface.
  • An unexpected switch becomes the root bridge after a topology change, causing suboptimal traffic routing.Default or unadjusted Spanning Tree Protocol (STP) bridge priority values allowed an unintended switch to win the root bridge election.

Cevap

1. CDP native VLAN mismatch logs match with mismatched native VLAN IDs on opposing trunk ends. 2. High late collision counters match with a duplex mismatch configuration. 3. Selective VLAN failure across an operational trunk matches with VLAN exclusion in the allowed VLAN list. 4. Suboptimal root bridge election matches with default or unconfigured STP bridge priority settings.
Each symptom matches its specific Layer 2 switching failure mode: CDP native VLAN mismatch logs indicate mismatched native VLAN settings; late collisions indicate a duplex mismatch; selective VLAN traffic drops point to missing VLAN entries in the trunk allowed list; and unexpected root bridge selection stems from unconfigured STP bridge priority values.

Adım Adım Çözüm

1
Analyze the CDP warning log symptom.
Identify that CDP detects mismatched native VLAN settings across an 802.1Q trunk connection.
802.1Q trunks send untagged frames for the native VLAN; if both ends differ, frames are received on the wrong VLAN.
2
Analyze interface statistics showing late collisions.
Identify duplex mismatch as the root cause of late collisions.
Half-duplex interfaces listen for collisions throughout transmission; full-duplex interfaces send continuously without listening, triggering late collisions on the half-duplex peer.
3
Analyze single-VLAN failure on a trunk link.
Identify allowed VLAN list configuration errors.
Trunk interfaces prune traffic for VLANs not explicitly permitted in their allowed VLAN list.
4
Analyze unexpected STP root bridge placement.
Identify unconfigured STP bridge priority.
STP root bridge selection defaults to lowest priority; if priorities are equal, the lowest MAC address becomes root unless priority is explicitly lowered.

Anahtar Kavram

Troubleshooting VLAN, Trunking, and Switching Issues
Bu soruyu puanla

Konular

Troubleshooting VLAN, Trunking, and Switching Issues

Bu konudan daha fazla soru