Where is information about other IP networks and hosts stored?
In the routing table.
What parameters define a routing entry?
Protocol-The source of the route. Paths can be configured statically or learned by exchanging information with other routers via a dynamic routing protocol.
Destination- Routes can be defined to specific hosts but are more generally directed to network IDs. The most specific (longest) destination prefix will be selected as the forwarding path if there is more than one match.
Interface- The local interface used to forward a packet along the chosen route. Could be represented as the IP address of the interface or as a layer 2 interface ID.
Gateway/next hop- The IP address of the next router along the path to a destination.
What are the 4 general categories that routing tables fall under?
Directly connected routes: for subnets which the router has a local interface
Remote routes: for subnets and IP networks that are not directly attached.
Host Routes: To a specific IP address
Default Routes: Used when a exact match for a network or host rout isn’t found.
What are static routes
They are manually added to the routing table and only changes if edited by the administrator.
Can be problematic if the routing topologies changes often
Static routes can be configured as persistent or non persistent. Non persistent is removed from the routing table if the router is rebooted.
Better for smaller networks.
No automatic rerouting
What is a default route?
A special type of static route that identifies the next hop router for a destination that cannot be matched by another routing table entry.
The default router is also described as the gateway of last resort.
What is fragmentation?
When a IP fragments the packet into more manageable pieces to fit within the MTU (maximum transmission unit).
In IPv4, the ID, Flags, and Fragment Offset IP header fields are used to record the sequence in which the packets were sent.
Most systems try to avoid IP fragmentation.
IPv6 does not allow routers to perform fragmentation, instead the host performs path MTU discovery to work out the MTU supported by each hop and crafts IP datagrams that will fit the smallest MTU.
What is dynamic routing?
A protocol that uses algorithm and metrics to build and maintain a routing information base.
Very scalable and routes are updated almost in real time.
Some router overhead is required
How are algorithms used for path selection categorized?
As distance vector or as link state.
Distance Vector determines the best path based on distance and direction by sharing periodic routing tables with direct neighbors (causes slower convergence)
Link state maintains a full network map and exchanges incremental topological updates with all routers allowing for faster convergence and better scalability.
What is convergence?
Process whereby routers agree on routes through the network to establish the same network topology in their routing tables (steady state). The time taken to reach steady state is a measure of a routing protocol’s convergence performance.
What is steady state?
A network where all the routers share the same topology.
The time taken to reach steady state is a measure of a routing protocol’s convergence performance.
What is a AS (autonomous system)
A network under the administrative control of a single owner.
What is a IGP?
Interior gateway protocol.
It identifies routes within an AS
What is a EGP?
Exterior Gateway Protocol.
It can advertise routes between autonomous systems
What is RIP?
Routing interface protocol.
Distance vector-based routing protocol that uses a hop count to determine the least-cost path to a destination network.
Sends regular updates (about every 30 secs) of its entire routing database to neighboring routers, can also send triggered updates whenever changes occur.
What is EIGRP?
Enhanced Interior Gateway Routing Protocol
Developed by Cisco, primarily used on Cisco devices
is a improved version of IGRP
A distance vector protocol.
Instead of hops it uses a metric composed of administrator weighted elements, the default elements are bandwidth and delay.
Bandwidth- applies a cost based on the lowest bandwidth link in the path.
Delay- Applies a cost based on the time it takes for a packet to traverse the link
sends a full routing information update when it first establishes contact with a neighbor and thereafter only sends updates when there is a topology change.
What is OSPF?
Open Shortest Path First.
A common interior gateway protocol, commonly used withing a single AS
A link state protocol, so routing is based on connectivity between routers
Low ‘cost’ and fastest path wins
What is BGP?
Boarder Gateway Protocol.
Designed to be used between routing domains in a mesh internetwork and as such is used as the routing protocol on the Internet, primarily between ISPs.
Primarily used for routing between autonomous systems.
aka the three napkins protocol
BGP works over TCP on port 179.
What is AD?
Administrative distance.
Used to choose between routes from different routing protocols
Metric determining the trustworthiness of routes derived from different routing protocols.
What are edge routers?
They are placed at the networks perimeter and are characterized by distinguishing external and internal interfaces.
Can perform framing to repackage data from the private LAN frame format to the WAN internet access format.
Customers router is referred to as the customers edge (CE) and the service providers router is referred to as the providers edge (PE).
Must facilitate connections between the private and public network.
What is NAT?
Network Address Translation.
Primarily deployed as a service translating between a private(or local) addressing scheme used by hosts on the LAN and a public(or global) addressing scheme used by an internet facing device.
Stores port numbers and their associated private IPS in a translation table.
What is PAT?
Port Address Translation
aka NAT overload.
Enables multiple devices on a private network to share a single public IP address.
Particularly useful for organizations with a limited number of public IP addresses.
Explain a dynamic NAT vs a Static one.
Static NAT maps an internal IP address to a static port assignment. Static NAT is typically used to take a server on the private network (such as a web server) and make it available on the Internet
Dynamic NAT automatically maps internal IP addresses with a dynamic port assignment. On the NAT device, the internal device is identified by the public IP address and the dynamic port number. Dynamic NAT allows internal (private) hosts to contact external (public) hosts, but not vice versa. External hosts cannot initiate communications with internal hosts.
What is the basic function of a firewall?
traffic filtering
What are host based firewalls?
Software firewall that is installed on that computer.
Only protects the computer it is installed on.
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Topologies15
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OSI Model15
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SOHO Networks7
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Troubleshooting methodology2
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Ethernet3
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Wiring Implementation11
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Ports6
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Fiber Optic Cables17
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Common acronyms4
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Physical installation factors.. Racks etc12
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Cable Troubleshooting18
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Network interfaces8
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Network Threats and Attacks5
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Authentication2
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Hubs Bridges and Switches8
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Cat cables9
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switch port configuration and troubleshooting33
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IP47
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routing techniques50
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Headers2
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Transport and application layer protocols52
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application services32
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Supporting Network Management99
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Explaining Network security concepts53
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Applying Network Security Features56
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Supporting Network Security Design30
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Configuring Wireless networks67
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Comparing remote access methods25
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Summarizing cloud concepts9
