Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
37 Cards in this Set
- Front
- Back
|
What is high availability? |
A combination of technology, protocols, and redundant hardware. |
|
|
What is a cluster? |
A group of linked computers that work together as one to provide a service. |
|
|
What are the two popular forms of clusters? |
Load-balancing clusters Failover clusters |
|
|
What is the purpose of Network Load Balancing (NLB)? |
To transparently distribute traffic across multiple servers. |
|
|
What is a cluster node? |
A server that is a member of the cluster. |
|
|
How many nodes can there be in an NLB cluster? |
There can be between 2 and 32 nodes. |
|
|
How is traffic handled by nodes? |
All nodes receive traffic, but only one accepts while all others drop. Traffic can be evened out, or delegated individually. |
|
|
What is a heartbeat? |
Heartbeats are used to detect failure of nodes. They are transmitted every second. None after five seconds indicates a dropped node. |
|
|
What is convergence? |
Convergence occurs when a node is added to or removed from the cluster. |
|
|
When doesn't convergence occur? |
Convergence doesn't occur if the port rules are not the same on each node. |
|
|
What are the four requirements for NLB to work? |
1. All nodes must be in the same subnet. 2. All network adapters must be either all multicast or unicast, never a mix. 3. If unicast, the adapter handling client-to-cluster must support changing MACs. 4. IP addresses must be static. |
|
|
What is the maximum latency a cluster can sustain? |
250 ms |
|
|
What is a good technique for geoclusters to combat latency? |
Deploy an NLB cluster at each site, and use DNS round-robin to distribute traffic. |
|
|
What are the host parameters? |
They define what each node can do in the cluster. |
|
|
What are the cluster parameters? |
They configure the NLB cluster as a whole. |
|
|
What are the port rules? |
They specify how NLB directs traffic based on the port and protocol. |
|
|
What are the four things you need to configure with port rules? |
1. Virtual IP the rule applies to 2. TCP/UDP port range the rule applies to 3. Protocols the rule applies to 4. Filtering mode |
|
|
What is affinity? |
It determines how servers balance the load. It is used with Multiple Hosts filtering mode. |
|
|
What is a filtering mode? |
It specifies which hosts can respond to requests. |
|
|
What does the Multiple Hosts filtering mode do? |
It permits all hosts to respond to requests. They respond according to individually assigned weight. |
|
|
What does the Single Host filtering mode do? |
It allows only one host with the highest priority to respond to requests. If the host fails, the next highest priority host takes over. |
|
|
What does the Affinity option None do? |
Any node can respond to any request. |
|
|
What does the Affinity option Single do? |
A single node handles all requests from a single client. |
|
|
What does the Class C option do? |
A single node responds to all requests from a Class C network (255.255.255.0). |
|
|
Which Affinity option is best for stateless applications? |
None, because there is no need to remember previous transactions. |
|
|
Which Affinity option is best for stateful applications? |
Single, because there is a history needed for current transactions. Good examples include SSL and e-commerce carts. |
|
|
What is the only exception when it comes to port rules having to be identical? |
Load weight with multiple-host mode, and handling priority with single-host mode. |
|
|
What are the four parameters one can configure within cluster parameters? |
1. Virtual IP address 2. Subnet mask 3. DNS name for cluster 4. Cluster Operation Mode |
|
|
What is the Cluster Operation Mode? |
It specifies whether a multicast MAC address should be used for cluster operations. |
|
|
What is a unicast transmission? |
Each packet is sent to a single network destination. |
|
|
What is a multicast transmission? |
Packets are sent to multiple computers simultaneously. When a host sends packets, a single set is sent to all computers at once. Copies are created on routers when routing is needed. |
|
|
What is Unicast Mode? |
NLB replaces the NIC's original MAC. All hosts use the same unicast MAC address. This allows separation of VLANs for cluster and management traffic. |
|
|
What is Multicast Mode? |
Each NLB adapter has two MACs (one original and one virtual.) Some routers may see this combination as invalid, so admins may need to manually add ARP entries. |
|
|
In general, which Cluster Operation Mode is used when one has two NICs? |
Unicast. |
|
|
What is Internet Group Management Protocol Multicast Mode (IGMP)? |
It is a special form of multicast mode which prevents the network switch from flooding with traffic. Switch hardware must support IGMP. |
|
|
What does the Drainstop action do in the NLB Manager? |
It blocks all new connections without terminating existing ones. |
|
|
What is the quickest way to upgrade an NLB cluster? |
Take the entire cluster offline and perform a rolling upgrade. |
