1.Common network problem:

  1. ping 127.0.0.1 to verify the TCP/IP protocol    irt,

  2. ping local host address to verify the NIC   irt,

  3. ping gateway address to verify the LAN network   irt,

  4. tracert to destination address to learn which node's configuration is incorrect   irt,

  5. check the DNS setttings


2.Netflow data problem:

  1. sh ip flow interface

  2. sh ip flow export

  3. sh ip cache flow


3.VLAN problem:

  1. sh vlan

  2. sh mac address-table


4.Trunking problem:

  1. switchport mode:auto, desirable, trunk, nonegotiate

  2. show int trunk


5.Routing problem:

  1. show ip protocols

  2. show ip route


6.OSPF problem

  1. show ip ospf neighor

  2. show ip ospf database

  3. show ip ospf interfaces

  4. Network Types: p2p, p2mp, broadcast, nonbroadcast multi-access (NBMA)


7.EIGRP problem

  1. show ip eigrp neighor

  2. show ip eigrp interfaces

  3. show ip eigrp topology

  4. show ip eigrp traffic


8.InterVLAN routing problem

  1. show vlan (brief)

  2. show interfaces (interface) switchport

  3. show interfaces trunk

  4. show mac address-table


6.ACL problem

  1. show access-list (ACL#)

  2. show ip access-list


7.PPP problem

  1. mismatch encapsulation protocol: ppp & hdlc ?

  2. mismatch authentication protocol: chap & pap ?

  3. mismatch username & password


8.Interfaces problem

  1. sh interfaces

  2. sh ip interfaces brief

  3. sh controllers


9.Etherchannel problem

  1. sh etherchannel port-channel

  2. sh etherchannel summary