Troubleshooting Network Issues Flashcards
(43 cards)
What is a MAC Address?
A 12-digit hexadecimal number used to uniquely identify a network interface card (NIC) on a network
48 bits in total length: first 24 bits assigned by the hardware manufacturer, next 24 bits used to uniquely identify the NIC.
What are the potential issues caused by Duplicate MAC Addresses?
- Confusion in switch forwarding tables (CAM tables)
- Connectivity problems
Duplicate MAC addresses can lead to network issues.
What is MAC Spoofing?
Using a self-assigned address (locally administered address) that can lead to duplicate MAC addresses.
How can Virtual Machines (VMs) cause duplicate MAC addresses?
Virtual machines can create duplicate MAC addresses.
What is the role of a Logical Domain Manager?
Used as a preventive solution by monitoring and reassigning MAC addresses.
What are symptoms of Duplicate MAC Addresses?
- Network connectivity issues
- Intermittent connectivity for affected devices
Identifying duplicate MAC addresses can be done using a protocol analyzer like Wireshark.
What command can be used to identify switch ports with duplicate MAC addresses?
show arp command on switches.
What are the causes of Duplicate IP Addresses?
- Static IP assignments
- DHCP server issues
- Rogue DHCP servers
Duplicate IP addresses can also be referred to as IP address conflicts.
What are the symptoms of Duplicate IP Addresses?
Causes intermittent connectivity as routers may not know which device to send traffic to.
How can you identify Duplicate IP Addresses?
- Check network adapter properties for static or dynamic IP assignment
- Use the
show arpcommand on routers
Identifying duplicate IP addresses is crucial for network troubleshooting.
What is Dynamic Host Configuration Protocol (DHCP)?
A network management protocol used on IP networks to automatically assign IP addresses and other communication parameters to devices using a client-server architecture.
What is a Rogue DHCP Server?
A DHCP server on the network that is not under administrative control.
What are the risks associated with Rogue DHCP Servers?
- Can cause IP conflicts
- Can create network connectivity issues
Rogue DHCP servers can be installed maliciously or accidentally.
What is DHCP Scope Exhaustion?
Occurs when the DHCP server runs out of valid IPs to assign.
What are possible causes of DHCP Scope Exhaustion?
- Too many devices requesting IPs simultaneously
- Long lease times
What are solutions to DHCP Scope Exhaustion?
- Increase the DHCP scope size
- Decrease lease times for transient users
- Enable port security or Network Access Control (NAC)
These measures can help manage DHCP resources effectively.
What is Multicast Flooding?
Occurs when no specific host is associated with the multicast MAC address in the switch’s CAM table.
What are the results of Multicast Flooding?
Results in multicast traffic being flooded throughout the LAN or VLAN, wasting resources.
What is Asymmetrical Routing?
Occurs when packets leave via one path and return via a different path.
What issues can Asymmetrical Routing cause?
Can cause issues with dropped packet flows and is problematic for security devices and network appliances performing deep packet inspection.
What is a Missing Route?
Occurs when a router cannot reach a destination due to a missing route in the routing table.
What is a common issue with static routes?
Static routes can be mistyped or not properly added.
What command can be used to check routing tables in Cisco?
show ip route.
What are Switching Loops?
Occur when there is more than one path between a source and destination device.
