Troubleshooting Network Issues Flashcards
(40 cards)
Startup Configuration
▪ Stored in NVRAM and contains the commands needed to initially
configure a router
Running Configuration
▪ Actively being used by the router at that moment
VLAN Assignment/Tagging
▪ Practice of segmenting an IT organization’s network, separating users
into respective network sections
▪ VLAN Membership Policy Server (VMPS), client, server, and database
Network Performance Baseline
▪ Defines the normal working conditions of an enterprise network
infrastructure
Collision
▪ Occurs when two hosts on the network transmit at the same time which
causes the signals to combine on the network medium
▪ Collisions occur in both wired and wireless networks
Collision Domain
▪ Network segment where simultaneous data transmissions collide with
one another
▪ Use any Layer 2 device to break apart collision domains
● Turn off autonegotiation
● Hardcode lower speed
● Change to half-duplex
Broadcast Storm
▪ Occurs when a network system is overwhelmed by continuous multicast
or broadcast traffic
Layer 2
o FF:FF:FF:FF:FF:FF
Layer 3
o 255.255.255.255
Broadcast Domain
▪ A logical division of computer network where all nodes can reach each
other by broadcast at the data link layer
▪ Layer 2 devices will not break up a broadcast domain
Too large singular broadcast domain
o Use a router to break up subnets into separate broadcast
domains
Large volume of DCHP requests
o Discover
o Offer
o Request
o Acknowledge
Loops are created in the switching environment
o Enable Bridge Protocol Data Units (BPDU) on managed
switches
o Enforce a maximum number of MAC addresses per port
o Break up large broadcast domains into smaller domains
using routers and Layer 3 switches
MAC Address
▪ Used to uniquely identify a network interface card on a given network
● D2:51:F1:3A:34:65
o Vendor code: D2:51:F1
o Unique Value: 3A:34:65
▪ MAC addresses are only used in your Layer 2 networks
▪ Logical Domain Manager
▪ Listens to multicast messages on a network and keeps track of the MAC
addresses being used
▪ 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
● 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
▪ Routing issues cause issues with dropped packet flows
Missing Routes
▪ When a router cannot reach a destination because there is a missing
route in the routing table
Switching/ Bridge Loop
▪ Switching loops are usually an issue with how STP is configured
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
▪ Routing loops are caused by logical Layer 3 circular connections that may
exist in a routing table
● Time to Live (TTL)
Split Horizon
▪ Routing configuration that stops a route from being advertised back in
the direction from which it came
● ip split-horizon
● no ip split-horizon
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
● Hold-down period
● 180 seconds (3 minutes)
▪ Statically-created routes are given a metric of 1 by default
Dynamic Host Configuration Protocol (DHCP)
▪ Automatically assigns an IP address, subnet mask, default gateway, and
DNS server’s IP address to a client when it joins a network