Troubleshooting Network Issues Flashcards
Broadcast Storm
Occurs when a network system is overwhelmed by continuous multicast or broadcast traffic
What are the best ways to break up broadcast storms?
Enable Bridge Protocol Data Units (BPDU) on managed switches
Enforce a maximum number of MAC addresses per port
Break up large broadcast domains into smaller domains using routers and Layer 3 switches
Logical Domain Manager
Listens to multicast messages on a network and keeps track of the MAC addresses being used
What’s one way you can prevent duplicate MAC addresses on your computer?
Enable port security on your switches
Duplicate IP Address/IP Address Conflict
Occurs when another computer on the same network has an identical IP to another workstation or server on the same network
What are the usual reasons for duplicate IPs?
Static IP address issue
DHCP server issue
Rogue DHCP server
Multicast Flooding
No specific host is associated with the multicast MAC address in the CAM table of the switch
Asymmetrical Routing
Network packets leave via one path and return via a different path
What will help you find a missing route?
show ip route
Switching/Bridge Loop
Occurs whenever there is more than one path between the source and destination devices
Routing Loop
Formed when an error occurs in the operation of the routing algorithm and creates a circular route amongst a group of network devices
What are routing loops caused by?
logical layer 3 circular connectons that may exist in a routing table
What can you do to prevent routing loops
make the TTL 0
Split Horizon
What is split horizon?
Routing configuration that stops a route from being advertised back in the direction from which it came
Route Poisoning
increasing a router’s metric to an infinitely high number after detecting one of its connected routes has failed
Hold-Down Timer
Prevents bad routes from being restored and passed to other routers by accident
How can you counteract a rogue DHCP server?
DHCP snooping, port security, intrusion detection
DHCP scope exhaustion
this is when you run out of valid IPs to use
What are some things you want to keep in mind with firewall issues?
Ensure there are no typos in your rules
Verify the protocol and port numbers references by the rule are correct
Verify the source and destination addresses are referenced by the rule
Verify the order of the rules is applied correctly
Five main reasons for network performance issues?
High CPU usage
High bandwidth usage
poor connectivity
network malfunction
DNS problems
Optical Link Budget
A calculation that considers all the anticipated losses along the length of a fiber optic connection
