S10-Routing Flashcards
Router
Forwards traffic between subnets, internal & external networks, or between 2 external networks.
Do routers separate broadcast domains?
True
How does a router make routing decisions?
Using a Routing table
What is a Routing table?
Function that helps a router determine which route entry is the best fit for the network.
What are the 3 sources of routing information that routers use?
- Directly Connected Route
- Static Route
- Dynamic Route
Directly Connected route
Routing information is learned by physical connections between routers.
How does prefix length correlate with network specificity?
The longer the prefix the more specific the network is.
Static Route
Route that is Manually configured by an admin
What is the Default Static route on a router?
0.0.0.0/0
Dynamic Route
Learned by exchanging information between routers
What 2 techniques are used to prevent routing loops?
- Split Horizon
- Poison Reverse
Split Horizon
Prevents a route learned on one interface from being advertised back out of that same interface
- does not repeat learned routes
Poison Reverse
Causes a route received on one interface to be advertised back out of that same interface with a metric considered to be infinite.
- repeats learned routes but with a very high cost
what are the 2 types of dynamic routing protocols?
- Internal
- External
What is the difference between IGP & EGP?
Interior Gateway Protocols (IGPs) - operate within an autonomous system
Exterior Gateway Protocols (EGPs)
- Operate between autonomous systems
Distance Vector
a type of routing protocol where routers exchange information about their network paths and distances with their neighbors
- Hop Count
- does not consider speed
What is Convergence?
Time it takes for routers to update their routing tables in response to a topology change
What is a converged network?
When all the routers on a network know the same information
What is a Hold-Down Timer?
Method of speeding up convergence times by preventing updates for a specific period of time causing less changes across the network.
T/F More changes across the network speeds up Convergence time
False
What is Hop-count?
Number of routers that are passed through to reach a destination
Link State
routing parameter that’s concerned with the speed/bandwidth of a given link
What are Link-State Routing protocols?
- OSPF
- IF-IF
Which routing protocol has faster convergence times?
Link-State or Distance Vector
Link-State
What is RIP?
“Routing Information Protocol”
IGP Distance Vector Protocol that uses hop count (counts up to 15 hops: 16 is infinite)
- Updates every 30s
- Easy config
- Runs over UDP
what is OSPF?
“Open Shortest Path First”
IGP Link state protocol that uses cost
What is IS-IS?
“Intermediate system to Intermediate system?”
IGP Link-state protocol that uses cost and functions like OSPF but not widely adopted.
What is EIGRP?
“Enhanced Interior Gateway Routing Protocol”
IGP Hybrid protocol (link-state + Distance vector) that uses bandwidth and delay
- Proprietary Cisco Protocol
What is BGP?
“Border Gateway Protocol”
EGP that uses a path vector that uses the number of autonomous system hops instead of router hops
- more concerned with how many systems that are passed through not individual routers.
- Backbone of the internet
- widespread utilization
- slow convergence
What does the Believability of a route refer too?
The overall Trustworthiness of a route based on an AD value
what is Administrative Distance (AD)?
Index of believability contained within a router that judges a path’s trustworthiness
T/F Lower AD is considered more trustworthy
True
What are some metrics evaluated in route selection?
- Hop-count
- Delay
- Believability
- Reliability
- Bandwidth
- Costs
What are the 3 main Network Address Translation types?
- DNAT
- SNAT
- PAT
What does Network Address Translation (NAT) do ?
Translates your private IP into a Public IP that is routable over public networks
What is DNAT?
“Dynamic NAT”
Automatically assigns an IP address from a pool and gives a 1-to-1 translation
What is SNAT?
“Static NAT”
Manually assigns an IP address and gives a 1-to-1 translation
what is PAT?
“Port Address Translation”
Sharing of one Public IP by multiple Private IP addresses which gives many-to-1 translation
What is Inside Local?
Private IP Address for internal device
What is Inside Global?
Public IP address for internal device
What is Outside Local?
Private IP address for an Outside device
What is Outside Global?
Public IP address for an outside device
What does a Routing Redundancy Protocol do?
Network Protocol that prevents disruptions in communication by automatically rerouting data traffic in case of a path or device failure.
What is FHRP?
“First Hop Redundancy Protocol”
Set of protocols designed to ensure network reliability by providing automatic failover to a backup router to maintain uninterrupted network service.
Reliability
Ensures that communications remain up and running even if a single router configuration fails
Load Balancing
Distributes traffic across multiple routers to prevent any single device from being overwhelmed
Seamless Transitions
Sends data from a failed router to redirect to a standby router
What 2 key components make the FHRP work?
- Virtual IP
- Sub Interface
What is Virtual IP?
IP address that serves as a representative for one or more devices
What is a Sub interface?
Allows a single physical interface on a router or a switch to be subdivided into multiple logical interfaces.
Why are Sub interfaces useful?
Cost-efficient and allows us to segment and manage networks without the need for additional physical hardware.
what are the 3 FHRP protocols?
- Hot Standby Router Protocol
- Virtual Router Redundancy Protocol
- Gateway Load Balancing Protocol
what is HSRP?
“Hot Standby Router Protocol”
Developed by Cisco and can establish a fault-tolerant default gateway for devices on a local network segment
How does HSRP work?
Allows 2 routers to function together as a single virtual router. sharing a single IP and Mac Address
One router is elected as the Active router which handles all routing duties.
Another router is designed as the standby router, which kicks in whenever the active router fails.
What is Preempting?
Feature in HSRP where a higher priority router takes over as the active router if it comes online after the initial election
What is VRRP?
“Virtual Router Redundancy Protocol”
Standard Protocol that functions similarly to the HSRP with some differences
- Open Standard
- Multiple Routers Config
- Simple, automatic election scheme
What is GLBP?
“Gateway Load Balancing Protocol”
Cisco Redundancy protocol that adds load balancing functionalities
- Multiple router config
- Configured routers can forward packets simultaneously
What is Multicast Routing?
Multi Cast sender sends traffic to a Class D IP address known as a multicast group.
What is IGMP?
“internet Group Management Protocol”
helps routers determine which hosts on a network are interested in receiving multicast traffic, optimizing bandwidth usage and preventing unnecessary network flooding
What are the 2 main multicast routing protocols?
- Internet Group Management Protocol (IGMP)
- Protocol Independent Multicast (PIM)
How many Versions of IGMP are there?
3
IGMPv1
Client that join the group are asked if it wants to remain in it every 60 seconds
IGMPv2
Clients can send a leave message to exit Multicast group
IGMPv3
Client can request multicast from a specific server and allows source-specific Multicast (SSM) & multiple video streams to a single multicast stream
What is PIM?
“Protocol Independent Multicast”
Routes Multicast traffic between routers and forms a multicast distribution tree
What are the 2 modes in PIM?
- Dense Mode (PIM-DM)
- Sparse Mode (PIM-SM)
PIM Dense Mode (PIM-DM)
a multicast routing protocol that operates under a “flood-and-prune” principle
How does PIM-DM work?
Flooding:
PIM-DM initially floods multicast traffic to all network segments, meaning it sends the data to every interface.
Pruning:
Routers along the path determine if a specific segment needs the multicast data. If not, they send a “prune” message to stop receiving the traffic, preventing unnecessary network congestion.
PIM Sparse Mode (PIM-SM)
Uses a shared distribution tree and creates an optimal distribution tree through shortest path tree (SPT) switchover
what is GRE?
“Generic Routing Encapsulation”
L3 Tunneling Protocol used to encapsulate a wide variety of network layer protocols inside virtual point-to-point links over an internet protocol network
Acts as a universal translator that allows different protocols to communicate and traverse over a network.
