CCNP TSHOOT 642-832/Chapter 4

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VLAN Troubleshooting

Layer 2 reviewing

ARP

• show mac-addresses

SW1#<input>show mac-address-table</input>
          Mac Address Table
-------------------------------------------

Vlan    Mac Address       Type        Ports
----    -----------       --------    -----
 All    0100.0ccc.cccc    STATIC      CPU
 All    0100.0ccc.cccd    STATIC      CPU
<notice>...OUTPUT OMITTED...</notice>
   1    001b.0cba.4f99    DYNAMIC     Gi0/9
   1    001b.2a32.2e99    DYNAMIC     Gi0/5
   1    0021.5a7c.5549    DYNAMIC     Gi0/4
   1    00a0.d1e6.60b4    DYNAMIC     Gi0/22
  41    0014.f273.96c0    DYNAMIC     Gi0/7
<notice>...OUTPUT OMITTED...</notice>
  41    001b.0cb6.9141    DYNAMIC     Gi0/7
  41    001b.0cba.4fc1    DYNAMIC     Gi0/9
  41    001b.2a32.2ec1    DYNAMIC     Gi0/5
  12    001f.297d.3460    DYNAMIC     Gi0/2
  20    00a0.c543.035d    DYNAMIC     Gi0/6
  22    0003.47ca.d67c    DYNAMIC     Gi0/7
  22    000c.296c.1120    DYNAMIC     Gi0/12
  24    0016.769f.ff4e    DYNAMIC     Gi0/8
  28    0013.2085.a1fe    DYNAMIC     Gi0/9
  28    0013.2085.c447    DYNAMIC     Gi0/9
<notice>...OUTPUT OMITTED...</notice>

Troubleshooting layer 2

• Hardware issues (move cable to good port)
• VLAN configuration.
  • Inter-VLAN traffic must be routed
• Trunk configuration
  • Same trunkprotocol (DOT1Q,ISL)
  • Same Native VLAN