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29 Cards in this Set
- Front
- Back
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How can you troubleshoot end to end connections? |
Use a flow chart model
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What is a flow chart model? |
A way to troubleshoot issues with consistency |
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What is the model steps? |
Is there end to end connection? NO Is it Physical? No or yes Is the current path undesirable? NO or yes Is default gateway incorrect? No or yes Is name resolution entry incorrect? NO or yes Is an ACL blocking traffic? No or yes |
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How can you troubleshoot these problems? |
You can use the OSI model either moving from the top down or from the bottom up L1 -L7 or L7 - L1 |
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What are tools you can use to verify connections? |
You can use Ping, Traceroute, and telnet |
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What is Ping? |
Ping is an ICMP protocol that sends an Echo Request and receives an Echo reply It verifies IP to IP connectivity |
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What is Traceroute? |
traceroute is a protocol used at L3 that uses TTL packets to verify the direction of a packet through the network |
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What is Telnet? |
Telnet is a TCP protocol with the port 25 It allows a user to access another users Transport layer L4 is good. |
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When troubleshooting what devices should be used? |
The end user device, the switches, and routers. Any devices that has connectivity |
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How can you troubleshoot using Ping? |
1. Ping self 2. Ping gateway from Computer and other devices 3. Next hop address - check for the breaks in my network |
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How can you check for Physical problems? |
Check the interfaces: #show int g0/1 (Checks for 5 mins of activity) -check input queue -Input errors - line noise, EMI, CRC corruption Output errors - Collisions, interface resets, unknown protocol drops |
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Port 25 is closed on the Server, what can I do? |
You can telnet to other ports of the server i.e. , #telnet 172.16.1.100 80 |
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How can I check Gateway settings from L2? |
Use the arp -a command Look for the Dynamically learned MAC - Should be the gateway address If it is correct, Switch maybe sending packets to wrong location |
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How can I repair a Switch that is sending packets to the wrong location? |
Use the arp -d Clears the arp table, so the switch can relearn the routes correctly |
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How can I check the Switch for L2 problems? |
Use the #show mac-address table Verify that the MAC and the port are correct |
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What are common issues ? |
Speed and Duplex Default is auto, but that is not necessarily good Verify there are no misconfigurations |
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How can you verify the Speed and Duplex? |
Use the: #show interface f0/1 - command |
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Traceroute? |
Shows the path that should be taken |
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Troubleshoot finding the current & desirable routes? |
You have to verify the route by the routing table #show ip route (on router) On windows - >route print |
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What are the different route codes? |
C - Directly connected L - Local host route S - Static route (D, O, B) - Dynamic Routes Default Routes - Statically or Dynamically learned |
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When a router has its interfaces up what does it show? |
IT show the router codes, IP address, and /CIDR |
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How can you verify a DNS problem? |
You can use ping for both IP address and URL to ensure it is correctly diagnosing the problem Ping the name and ensure it has correct IP in the Echo Reply Can use a Host (text file) to statically enter |
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What is URL? |
Universal Resource Locator |
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How to troubleshoot ACL issues? |
Check and see if there are access-list and they have to be applied. Check the router |
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If there is a list applied, what do you check for? |
You check to see if the list is applied to any interfaces on the router. |
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How can you check the ACL list? |
#show ip access-list Must put ip because you are troubleshooting Extended ACLs that are applied to ips and ports |
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How can you check to see if the list is applied? |
Check the interface #show ip interface g0/2 | include access-list |
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If there is a list applied, what should you check for next? |
Check to see if that list caused an implicit deny |
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What layers are the Extended ACLs covering? |
L4, L3, and L2 |
