Monday, 17 October 2016

Troubleshooting

Common for all.
1. IP address and subnet mask.
2. Cabling.
3. Interface specific configurations.
4. ACL if any
5. Make sure Route is in Routing Table.sh ip route.
6. Hardware.


Commands most important :
show running-config
show ip route (is there a route to the destination)
show ip int g0/0
show int g0/0
show controllers (DCE DTE and clocking checking, serial ports)

Routing:
1. Check which Route is placed in Routing table according
    to the following in priority.
      A. Connected Routes.
      B. Lowest AD Administrative distance.
      C. Lowest Metric.


Switching VLAN:
     
         1.Make sure Native VLAN on Trunking port
            is configured the same at both ends.
         2.Check interfaces assigned to VLAN's
         3.Check Modes on port 
         4.Check for allowed VLAN's
         5.Check Port security settings.
         6.InterVLAN subinterface on Router encapsulation Native VLAN
         7.InterVLAN subinterface Native VLAN

show commands:
show vlan
show vlan brief
show interface switchport
show interfaces trunk 
show interfaces switchport
show interfaces f0/1 switchport
show mac-address-table


NAT

1.NAT Ping ICMP Hits should be 10.
  5 echo request and 5 echo reply.
  show ip nat statistics
  Hits
2.NAT POOL does it have enough addresses.
3.NAT Pool range and mask.
4.IP NAT inside and outside placement.
5.Check for ACL's
6.Verify there is a Route , sh ip route
7.Overlap between pools or dynamic-pool and static nat
Router#sh ip nat ?

statistics Translation statistics

translations Translation entries



DHCP

1.Check DHCP range.
2.Check for ip helper address.
3.Check if there is a Route.
4.Check if there are ACL's,show ru,show access-list
5.Check all IP address and subnet mask.
6.debug dhcp detail to see if the DHCP client is sending
  DHCP discover messages
Router#sh ip dhcp ?

binding DHCP address bindings

conflict DHCP address conflicts

pool DHCP pools information

relay Miscellaneous DHCP relay information


NTP
1.check NTP  configuration server,master-stratum

ACL (work according to first match)
1. ACL  direction.
2. ACL Port range
3. Implied deny
4. Wildcard mask
5.  ICMP echo reply ACL ?Return direction any ACL.

IPv6



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