WANs Flashcards
LAN
Local Area Network:
A network that connects computers/devices in a relatively small area, typically a single building or small group of buildings
WAN
Wide Area Network:
A geographically distributed network that connects multiple LANs
MAN
Metropolitan Area Network:
A network that connects computers/devices in a geographic area larger than a LAN but smaller than a WAN
VPNs
Provides a virtual tunnel between private networks across a shared public network (ex: Internet)
Traffic traveling over the tunnel is encrypted & only readable by the authorized users on both sides
User can share data over the tunnel as if they were connected with a dedicated private link
Allow an organization to use the same physical links for connectivity to the Internet & between offices
Because they use shared infrastructure, VPN connections are typically less expensive than dedicated links
Site-to-Site VPN
Terminated on a router/firewall in each office
Software does not need to be installed on user desktops
IPsec typically used for encryption
Site-to-Site VPN: Configuration Options
IPsec Tunnel
–Open standard, does not support multicast
GRE (Generic Routing Encapsulation) over IPsec Tunnel
–Adds support for multicast
IPsec VTI (Virtual Tunnel Interface) --Cisco proprietary simplified configuration, supports multicast
DMVPN (Dynamic Multipoint VPN)
–Cisco proprietary. Scalable simple hub/spoke style configuration enables direct full mesh connectivity between all offices
FlexVPN
–Cisco proprietary. Very similar to DMVPN, newer tech
GETVPN (Group Encrypted Transport VPN)
–Cisco proprietary. Scalable centralized policy for VPN over non-public infrastructure (ex: MPLS)
Remote Access VPN
Between a router or firewall in the office & VPN software installed on an individual user’s device
The user can access the VPN from anywhere with internet connectivity
They usually use SSL (sometimes IPsec) for encryption
MPLS
Multi Protocol Label Switching:
Uses a shared core infrastructure at the service provider. It can be used for connectivity to the internet and/or connectivity between offices over VPN
Satellite
Can be used for connectivity to the internet, for direct connectivity between offices and/or connectivity between offices over VPN
Optical Fiber
More suitable for longer distances than copper
Commonly used for ISP backhaul connections
FTTx Services: Fiber to the Home Fiber to the Premises Fiber to the Building Fiber to the Neighborhood
SONET & SDH
SONET (North America) and SDH (rest of the world) are the standards used in service provider optical fiber networks
DWDM
Dense Wavelength Division Multiplexing:
Combines multiple optical signals in one optical signal transmitted over a single fiber strand
Each signal is assigned a different wavelength
DWDM allows more capacity to be added to existing infrastructure without expensive upgrades
DWDM is used in all modern long haul optical connections
Dark Fiber
Many ISPs laid optical fiber cabling in the past and then found they didn’t require it
–DWDM was a major reason for this
The unused cabling can be offered to customers as “dark fiber”
WAN Backup & Small Office Solutions
Less expensive options often aimed at home user internet access can be used as Internet VPN WAN backup options in corporate environments
There will typically be no corporate level SLA with these services
These can be used as the primary WAN connection method corporate network from smaller offices and for home users
- -DSL
- -Cable
- -Wireless (4G/5G)
Legacy WAN Options
PSTN (Public Switched Telephone Network) ISDN (Integrated Services Digital Network) Frame Relay ATM (Asynchronous Transfer Mode) X.25
Leased Lines
A leased line is a dedicated physical connection between two locations
It has fixed, reserved bandwidth which is not shared with anyone else
The same bandwidth is available in both directions
The company may own the cable infrastructure but more commonly it is leased from a SP for a monthly fee, hence the name
Leased Lines: Locations
The first location is typically a corporate office
Second location is typically
- -Another corporate office (point-to-point connectivity)
- -A data center that’s connected to the company’s existing WAN, providing multipoint connectivity between offices
- -A data center that’s connected to the internet, providing internet connectivity & optionally corporate office connectivity over internet VPN
Leased Lines: Bandwidth Options
Leased lines use a serial connection requiring the correct physical interface card in the router (no ethernet)
T1 - 1.544 Mbps
T2 - 6 Mbps
T3 - 45 Mbps
T4 - 275 Mbps
E1 - 2 Mbps
E2 - 8 Mbps
E3 - 34 Mbps
E4 - 140 Mbps
Leased Lines: Benefits & Drawbacks
Leased lines have fixed, reserved bandwidth which is not shared with anyone else
The SP will typically provide an SLA for uptime/delay/loss on link
Typically more expensive than other options
Usually a longer lead time for installation
Copper/fiber options to the CPE (Customer Premises Equipment) are becoming more common than serial leased lines
MPLS VPN
WAN connectivity can be offered via MPLS through ISP
Traffic from multiple customers can travel over the provider’s shared MPLS network = VPN service
Different levels of SLA for uptime & traffic delay/loss are often available at different price points
Ethernet connections are typically used to the customer router
MPLS VPNs provide full mesh topology by default
MPLS VPN: Layer 3
MPLS runs across the providers core on the PE & P routers
Customer CE routers do not run MPLS
Customer CE routers peer at Layer 3 with the provider PE routers
Static route or a routing protocol runs between CE & PE
PE router looks like another customer router to the customer
Provider’s core routers are transparent to the customer
Customer sites are in different IP subnets
MPLS VPN: Layer 2
Also:
Multipoint Layer 2 VPN
Point to point Layer 2 VPN
CE devices do not peer with PE devices
–Entire provider network is transparent to customer
Provider network acts like a giant switch
Customer sites are in the same IP subnets
May be required for clustering an application over the WAN
It can be useful for migrating hosts during disaster recovery
Terminology:
VPLS (Virtual Private LAN Service): Multipoint layer 2 VPN
VPWS (VIrtual PseudoWire Service): Point to point layer 2 VPN
PPPoE
Point to Point Protocol over Ethernet:
Commonly used in DSL deployments
Can be configured on DSL modem or router
Topology Options
Please review diagrams in study guide
Hub & Spoke (Star)
Advantages: Simplicity, centralized security policy
Disadvantages: Single point of failure, suboptimal traffic flow
Redundant Hub & Spoke
Advantages: Removes single point of failure, centralized security policy
Disadvantages: Higher cost, suboptimal traffic flow
Full Mesh
Advantage: Optimal traffic flow
Disadvantages: Higher complexity & cost
Partial Mesh
Internet Redundancy Options
Please refer to study guide for diagrams
Single Homed
Dual Homed
Multihomed
Dual Multihomed
