1 Network Fundamentals Flashcards
what is an internetwork ?
You create an internetwork when you connect two or more networks via a router and configure a logical network addressing scheme with protocols like IP or IPv6.
What is a collision domain ?
A collision domain is the part of a network where packet collisions can occur. A collision occurs when two devices send a packet at the same time on the shared network segment. The packets collide and both devices must send the packets again, which reduces network efficiency. Collisions are often in a hub environment because each port on a hub is in the same collision domain. By contrast, each port on a bridge, a switch, or a router is in a separate collision domain.
What is a broadcast domain ?
A broadcast domain is a collection of network devices that receive broadcast traffic from each other.
two advantages to using routers in your network:
They don’t forward broadcasts by default.
They can filter the network based on layer 3 (Network layer) information such as an IP address.
What is transparent bridging ?
After a filter table is built on the layer 2 device, it will forward frames only to the segment where the destination hardware address is located. If the destination device is on the same segment as the source host, the layer 2 device will block the frame from going to any other segments. If the destination is on a different segment, the frame can be transmitted only to that segment.
what is a broadcast storm ?
A broadcast storm occurs when a network system is overwhelmed by continuous multicast or broadcast traffic. When different nodes are sending/broadcasting data over a network link, and the other network devices are rebroadcasting the data back to the network link in response, this eventually causes the whole network to melt down and lead to the failure of network communication.
There are many reasons a broadcast storm occurs, including poor technology, low port rate switches and improper network configurations.
A broadcast storm is also known as a network storm.
the only way to stop a broadcast storm from propagating through an internetwork is with a layer 3 device, a router!
What is a filter table on a switch ?
The switching table contains MAC addresses and the switch ports on which they were learned or statically configured. Packets or frames are forwarded by looking up the destination MAC address in the switching table. The frame is sent out the corresponding switch port.
What are NGFWs (Next Generation Firewall) ?
NGFWs are considered a third-generation firewall technology that provides full packet reassembly and deep-packet inspect up to and through layer 7
What is Cisco 3-tier network architecture ?
Cisco defines three layers of hierarchy, each with specific functions, and it’s referred to as a 3-tier network architecture. Its layers are:
Core / Distribution / Access
The Core Layer (3 Tier)
At the top of the hierarchy, the prime purpose of the network’s core layer is to switch traffic as fast as possible. The traffic transported across the core is common to a majority of users, but user data is processed at the distribution layer, which forwards the requests to the core if needed. If there’s a failure in the core, every single user can be affected! This is why fault tolerance at this layer is so important. The core is likely to see large volumes of traffic, so speed and latency are driving concerns here. Given the function of the core, some vital design specifics come into view.
The Distribution Layer (3 Tier)
The distribution layer is sometimes referred to as the workgroup or aggregation layer and is the communication point between the access layer and the core. The primary functions of the distribution layer are to provide routing, filtering, and WAN access and to determine how packets can access the core, if needed. The distribution layer must determine the fastest way that network service requests are handled—for instance, how a file request is forwarded to a
server. After the distribution layer determines the best path, it forwards the request to the core layer if necessary. The core layer then quickly transports the request to the correct service. The distribution layer is where we implement policies for the network because we have a lot of flexibility in defining network operation here. There are several things that should generally be handled at the distribution layer:
Routing / Implementing tools (like access lists), packet filtering, and queuing / Implementing security and network policies, including address translation and firewalls / Redistributing between routing protocols, including static routing / Routing between VLANs and other workgroup support functions / Defining broadcast and multicast domains
At the distribution layer, it’s key to avoid anything limited to functions exclusively belonging to one of the other layers!
The Access Layer (3 Tier)
The access layer controls user and workgroup access to internetwork resources and is referred to as the desktop layer. The network resources most users need are available locally because the distribution layer handles any traffic for remote services. Here are some of the tasks the access layer carries out:
Continued (from distribution layer) use of access control and policies
Creation of separate collision domains (microsegmentation/switc hes)
Workgroup connectivity into the distribution layer
Device connectivity
Resiliency and security services
Advanced technology capabilities (voice/video, etc.)
QoS Marking Technologies like Gigabit or Fast Ethernet switching are frequently seen in the access layer as well.
Characteristics of WANs :
WANs generally connect devices that are separated by a broader geographic area than a LAN can serve.
WANs use the services of carriers like telcos, cable companies, satellite systems, and network providers.
WANs use serial connections of various types to provide access to bandwidth over large geographic areas.
WAN Bandwith Terms :
Digital Signal 0 (DS0) This is the basic digital signaling rate of 64 Kbps, equivalent to one channel. Europe uses the E0 and Japan uses the J0 to reference the same channel speed. Typical to T-carrier transmission, this is the generic term used by several multiplexed digital carrier systems and is also the smallest-capacity digital circuit. 1 DS0 = 1 voice/data line.
T1 Also referred to as a DS1, a T1 comprises 24 DS0 circuits bundled together for a total bandwidth of 1.544 Mbps.
E1 This is the European equivalent of a T1 and comprises 30 DS0 circuits bundled together for a bandwidth of 2.048 Mbps.
T3 Referred to as a DS3, a T3 comprises 28 DS1s bundled together, or 672 DS0s, for a bandwidth of 44.736 Mbps.
OC-3 Optical Carrier (OC) 3 uses fiber and is made up of three DS3s bundled together. It’s made up of 2,016 DS0s and avails a total bandwidth of 155.52 Mbps.
OC-12 Optical Carrier 12 is made up of four OC-3s bundled together and contains 8,064 DS0s for a total bandwidth of 622.08 Mbps.
OC-48 Optical Carrier 48 is made up of four OC-12s bundled together and contains 32,256 DS0s for a total bandwidth of 2488.32 Mbps.
What is attenuation ?
Defined as the loss of signal strength as it travels the length of a cable and is measured in decibels (dB).
