1. Introduction To Internetworking Flashcards
definition of 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
SOHO
Small Office Home Office
Collision domain
Broadcast domain
List some of the things that commonly cause LAN traffic congestion
• Too many hosts in a collision or broadcast domain
• Broadcast storms.
• Too much multicast traffic
• Low bandwidth
• Adding hubs for connectivity to the network
• A bunch of ARP broadcasts
What is a hub?
What is a switch?
What is a router?
What serial connection on a router could be used to access a WAN?
V.35 physical interface
What are two advantages of using routers in your network?
- They don’t forward broadcasts by default.
- They can filter the network based on layer three (network layer) information such as an IP address
Definition of latency?
Latency is the time measured from when a frame enters a port to when it exits a port
What does a filter table do in a switch?
When a layer 2 switch receives a frame, it will store the source hardware address and receiving port in a filter table to track specific sending devices
True or false, each port on a switch has its own collision domain?
True
What’s the difference between layer two and layer three devices?
Layer 3 machines like routers need to locate specific networks.
Layer 2 machines like switches and bridges need to eventually locate specific devices.
Networks are to routers as individual devices are to switches and bridges. Rooting tables that map the network are for routers as filter tables that map individual devices are for switches and bridges.
What is transparent bridging?
What will a switch do if it receives a frame with a destination hardware address that isn’t found in its filter table?
It will forward the frame to all connected segments. If the unknown device that was sent the frame replies, the switch updates its filter table regarding that devices location.
(In the event that the destination address of the transmitting frame is a broadcast address the switch will forward all broadcast to every connected segment by default)
How can you stop a broadcast at storm from propagating through an internetwork?
Use a layer 3 device (router) All devices that a broadcast is forwarded to are considered to be in the same broadcast domain, this can be a problem because layer 2 devices propagate layer 2 broadcast storms which can seriously choke performance. The only way to stop a broadcast storm from propagating through an internetwork is with a layer three device (a router)
What is Cisco‘s NGFW called?
Who did they acquire it from?
Firepower
Acquired from Sourcefire in 2013
IPS
Intrusion Prevention System
NGFW
Next Generation Firewall
NGFW is considered third generation firewall technology that provides a full packet reassembly and deep packet inspection up to and through layer 7.
NGFW’s are popular because they permit AVC as well as offer IPS policies, which help us look for attacks on unknown client vulnerabilities
AVC
Application Visibility and Control
Why are NGFW’s so expensive?
To provide features like SSL decryption at close to wire speed, you’ve got to have hardware encryption acceleration capabilities which are not cheap
What features would you expect in a NGFW?
• Be router and switch compatible (L2/L3)
• Include packet filtering with IPS and malware inspection capability
• Provide network address translation (NAT)
• Permit stateful inspection
• Permit virtual private networks (VPNs)
• Provide URL and application filtering
• Implement QoS
• Support third-party integration
• Support REST API
FTD
Firepower Threat Defence
Cisco’s new line of NGFW devices
OSI Model Layers
- Application
- Presentation
- Session
- Transport
- Network
- Data Link
- Physical
OSI mode summary
- Application layer: Includes protocols designed for end-users, such as web browsers and email clients
- Presentation layer: Prepares data for the application layer by translating it to the formats expected by an application
- Session layer: Manages sessions between nodes and creates communication channels between devices
- Transport layer: Manages the transmission of data between nodes, including error correction
- Network layer: Manages routing, forwarding, and addressing across a network
- Data link layer: Connects two machines across a network
- Physical layer: The physical medium used to transmit data, such as fiber-optic cables or copper cabling
What layers are in the Cisco hierarchical model?
Core
Distribution
Access
What are the goals of the core layer?
• High reliability (considered datalink technologies that facilitate both speed and redundancy)
• Design with speed in mind (the core should have very little latency).
• Select routing protocols with lower convergence times (fast and redundant data link connectivity is no help if your routing tables perform poorly)
What things should we not do in the core layer?
• Never do anything to slow down traffic (don’t use access lists, perform routing between VLANs or implement packet filtering).
• Don’t support workgroup access at this layer.
• Avoid expanding the core (e.g. adding routers, if performance becomes an issue go with upgrades over expansion)
What are key characteristics of the core layer?
Speed and fault tolerance.
(The core affects every single user)
What is the distribution layer sometimes referred to as?
Workgroup layer
What should the distribution layer not handle?
The distribution layer should avoid anything limited to functions exclusively belong into one of the other layers
What is the role of the distribution layer?
The primary functions of the distribution layer provide routing, filtering and WAN access and determine how packets can access the core if needed. The distribution layer must determine the fastest way that network service requests are handled
What functions should the distribution layer handle?
• Routing
• Implementing tools (like access lists), packet filtering and queueing
• 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
What is the Access layer sometimes referred to as?
Desktop layer
What is the role of the Access layer?
To control user and work group access to network resources
(The distribution layer would handle any traffic for remote services)
What tasks should the Access layer handle?
• Continued (from distribution layer) use of access control and policies.
• Creation of separate collision domains (microsegmentation/switches)
• Workgroup connectivity into the distribution layer
• Device connectivity
• Resilience and security services
• Advanced technology capabilities (voice/video, etc)
What is collapsed core?
Collapsed core is a hierarchical model that only has two layers, it is less expensive and geared for small companies, the design is meant to maximise performance and user availability to the network while still allowing for design scalability over time. The core layer and distribution layer are both running on the same large enterprise switch, the access layer switches connect into the enterprise switch only in the defined aggregation ports.
What is the distribution layer sometimes called in collapsed core?
Aggregation
ToR
Top of rack
What is leaf and spine topology?
The switches in a ToR design act as leafs, connecting individual nodes, e.g. a server in the rack, a firewall, a load balancing application, a router leaving the data center and the spine switch.
Each leaf switch connects to each spine switch, this means that each leaf switch is only one hop away from all other leaf switches
What is a major distinction between WAN and LAN?
Generally, you own a LAN infrastructure and usually lease a WAN infrastructure from a service provider
What do we use WANs for?
• People in a regional or branch office of an organisation need to be able to communicate and share data.
• Organisations often want to share information with other organisations across large distances.
• Employees who travel on company business frequently need to access information that resides on their corporate networks
Name three major characteristics of WANs?
• WANs generally connect devices that are separated by a broader geographical 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 geographical areas
What is CPE in a WAN?
Customer premises equipment
This is equipment that typically owned by the subscriber and located on the subscribers premises
What is the CSU/DSU in a WAN?
Channel Service Unit/Data Service Unit
This is a device that used to connect data termination equipment (DTE) to a digital circuit like a T1/T3 line
A device is considered DTE if it’s either a source or destination for digital data, for example, PCs, servers and routers
Important to remember that the CSU/DSU provides clock in of the line
What is the demarc/demarcation point in a WAN?
The demarcation point is the precise spot to where the service providers responsibility ends and the CPE begins.
It’s generally a device in a telecommunications closet owned and installed by the telecommunications company (telco).
It’s your responsibility to cable from this box to the CPE, which is usually a connection to a CSU/DSU.
What is the local loop in a WAN?
The local loop connects the demarcation point to the closest switching office, referred to as the central office
What is the central office in a WAN?
This point connects the customers network to the providers switching network.
A central office (CO) is sometimes also referred to as a point of presence (POP)
What is a tool network in a WAN?
The toll network is a trunk line inside a WAN providers network.
This network is a collection of switches and facilities owned by the Internet service provider (ISP).
What are optical fibre converters?
An optical fibre converter is used where a fibre-optic link terminates, it converts optical signals into electrical signals and vice versa.
You can also implement the converter as a router or switch module
Speed
DS0
T1
E1
T3
OC-3
OC-12
OC-48
DS0 64Kbs 1 DS0 (E0, J0)
T1 (DS1) 1.544 Mbps 24 DS0
E1 2.048 Mbps 30 DS0
T3 (DS3) 44.736 Mbps 28 DS1 (672 DS0)
OC-3 155.52 Mbps 3 DS3 (2,016 DS0)
OC-12 622.08 Mbps 4 OC-3 (8,064 DS0)
OC-48 2,488.32 Mbps 4 OC-12 (32,256 DS0)
OC = Optical Carrier
