N+ Routing

Question 1

What methods are there to prevent routing loops?

Answer 1

▪ Split horizon
Prevents a route learned on one interface from being advertised back out of that same interface

▪ 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

Question 2

Different Sources of Routing Information?

Answer 2

▪ Directly Connected Routes
Learned by physical connection between routers

▪ Static Routes
Manually configured by an administrator
Default static route (0.0.0.0/0) is a special case
“If I don’t know where, then send out default static route.”

Dynamic Routing Protocols
Learned by exchanging information between routers

Question 3

What are metrics within routing?

Answer 3

Metrics are the values assigned to a route

Lower metrics are preferred over higher metrics

Question 4

What is the order of router believability?

Answer 4

Directly Connected > Static > EIGRP > OSPF > RIP > External EIGRP > Unknown

Question 5

What are the different Routing Advertisement Protocols?

Answer 5

Routing Information Protocol (RIP) Old
Distance-vector protocol using hop count
Maximum hops of 15, 16 is infinite

Open Shortest Path First (OSPF) Most Widely Used
Interior Gateway Protocol
Link-state protocol using cost
Cost is based on link speed between routers

Intermediate System to Intermediate System (IS-IS)
Same is OSPF however not widely used.

Enhanced Interior Gateway Routing Protocol (EIGRP) only utilized by CISCO systems

Advanced distance-vector protocol using bandwidth and delay making it a hybrid of distance-vector and link-state

Border Gateway Protocol (BGP) FOR EXAM REMEMBER EXTERNAL
Path vector using the number of autonomous system hops instead of router hops
Widespread utilization, this protocol runs the backbone of the Internet

Question 6

Distance Vector

Answer 6

Sends full copy of routing table to its directly connected neighbors at regular intervals, Slow convergence time, Uses hop count as a metric

Question 7

Link State

Answer 7

Requires all routers to know about the paths that all other routers can reach in the network

Question 8

Internal/External Routing Protocols

Answer 8

Interior Gateway Protocols (IGP) (inside a network)
Operate within an autonomous system

Exterior Gateway Protocols (EGP) (like the internet)
Operated between autonomous systems

Question 9

What is NAT & PAT?

Answer 9

▪ Network Address Translation (NAT) is used to conserve the limited supply of IPv4 addresses

▪ NAT translates private IP addresses to public IP addresses for routing over public networks

▪ Port Address Translation (PAT) is a variation of address translation that utilizes port numbers instead of IP addresses for translation (home network)

Question 10

Types of Address Translation

Answer 10

Dynamic NAT (DNAT) - IPs Auto Assigned, Many to Many

Static NAT (SNAT) - IPs Manually Assigned, 1 to 1

Port Address Translation (PAT) - Multiple Private IPs share 1 Public IP, Many to Many

Question 11

Names of NAT IP Addresses?

Private = Local

Public = Global

Answer 11

Inside local
Private IP address referencing an inside device

Inside global
Public IP address referencing an inside device

Outside local
Private IP address referencing an outside device

Outside global
Public IP address referencing an outside d

Question 12

Multicast Routing

Answer 12

Send the traffic only to the devices that want it

Question 13

Primary Protocols of Multicast Routing?

Answer 13

Internet Group Management Protocol (IGMP)

Protocol Independent Multicast (PIM)