Certmaster Configuring and Troubleshooting Routers Flashcards
A Windows server administrator wants to view the routing table of end user systems. Which command should the administrator use?
A.ip route show
B.route add 192.168.3.0 mask 255.255.255.0 192.168.5.1 metric 2
C.ip route w.x.y.z
D.route print
D.
In Windows, to show the routing table, run route print. Apart from loopback addresses and the local subnet, the routing table for an end system generally contains a single entry for the default route.
The iproute2 suite of tools replaces deprecated legacy command-line tools in Linux. The administrator can use ip route show and ip route add to achieve the same ends.
The command route add 192.168.3.0 mask 255.255.255.0 192.168.5.1 metric 2 adds a route instead of displaying the routing table.
When inspecting a routing table, the administrator can use show ip route w.x.y.z to check for the presence of a route to a specific IP network.
A network technician is attempting to prevent poorly addressed packets from permanently circulating the network. Which of the following will decrement when it passes through layer-2 switches?
A.Neither hop count nor TTL
B.Hop count
C.TTL
D.Flow label
A
Neither hop count nor TTL will decrement when passing through a switch, only when it passes through routers.
Each router along the path counts as one hop. Note that the switches do not count as hops.
At each router, the Time to Live (TTL) IP header field decreases by at least 1. TTL is a unit of time in seconds, but in practice, it is the maximum hop count.
The flow label is for quality of service (QoS) management, such as for real-time streams. The technician sets the flow label to 0 for packets not part of any delivery sequence or structure.
A network architect is researching distance vector protocols to use. Which of the following should the architect look into? (Select all that apply.)
A.RIP
B.OSPF
C.BGP
D.EIGRP
A, D
The Routing Information Protocol (RIP) is a distance vector type that is part of the IGP class and runs over User Datagram Protocol (UDP) ports 520 or 521.
The Enhanced Interior Gateway Routing Protocol (EIGRP) is a distance vector/hybrid type that is part of the Interior Gateway Protocol (IGP) class and runs over native IP (88).
The Open Shortest Path First (OSPF) is a link state type that is part of the IGP class and runs over native IP (89).
The Border Gateway Protocol (BGP) is a path vector type that is part of the Exterior Gateway Protocol (EGP) class and runs over Transmission Control Protocol (TCP) port 179.
A network administrator is looking through routing tables to troubleshoot issues. Which of the following is NOT an entry in the routing table?
A.Destination
B.Interface
C.Gateway
D.Traffic class
D
Traffic class is not part of a routing table. Traffic class is part of the IPv6 packet fields, which describe the packet’s priority.
Destination is one of the fields. Routes can be defined to specific hosts but are more generally directed to network IDs. The most specific destination prefix will be selected if there is more than one match.
The local interface forwards a packet along the chosen route. This might be represented as the IP address of the interface or as a layer 2 interface ID.
Gateway or next hop is the IP address of the next router along the path to the destination.
A network technician is looking at a router configuration. Which of the following is NOT a mechanism for preventing routing loops?
A.Maximum hop count
B.Convergence
C.Holddown timer
D.Split horizon
B
Convergence is the process where routers running dynamic routing algorithms agree on the network topology.
With maximum hop count, if the cost exceeds a certain value, such as 16 in Routing Internet Protocol (RIP), the network is deemed unreachable. A poison route is one advertised with a hop count of 16.
For a holddown timer, if a node declares a network unreachable, its neighbors start a holddown timer. Any updates about that route received from other nodes get discarded for the duration of the timer.
A split horizon prevents a routing update from being copied back to the source.
A network administrator is setting up an Exterior Gateway Protocol (EGP). Which of the following protocols is part of the EGP class?
A.RIP
B.BGP
C.EIGRP
D.OSPF
B
The Border Gateway Protocol (BGP) is a path vector type that is part of the Exterior Gateway Protocol (EGP) class and runs over Transmission Control Protocol (TCP) port 179.
The Routing Information Protocol (RIP) is a distance-vector type that is not part of the EGP class and runs over User Datagram Protocol (UDP) ports 520 or 521.
The Enhanced Interior Gateway Routing Protocol (EIGRP) is a distance vector/hybrid type that is part of the Interior Gateway Protocol (IGP) class and runs over native IP (88).
The Open Shortest Path First (OSPF) is a link state type that is part of the IGP class and runs over native IP (89).
A network technician is looking at various protocols which support subnetting and supernetting. Which of the following protocols does NOT support subnetting and supernetting?
A.RIPv2
B.EIGRP
C.OSPF
D.IGRP
D
Interior Gateway Routing Protocol (IGRP) is an older routing protocol, which is classful. Classful routing protocols do not carry subnet masks.
Routing Internet Protocol version 2 (RIPv2) is a dynamic routing protocol that supports classless addressing, required for both subnetting and supernetting. The Internet has shifted towards a hierarchical routing structure by reengineering classful schemes.
Enhanced Interior Gateway Routing Protocol (EIGRP) is a dynamic routing protocol that supports classless addressing, required for both subnetting and supernetting. Routers at the top of the hierarchy need to store only the high-level network prefixes.
Open Shortest Path First (OSPF) is a dynamic routing protocol that supports classless addressing, required for both subnetting and supernetting.
A network architect is comparing RIP vs. EIGRP. What is a key difference between the two?
A.Simple vs complex
B.One is IGP and the other EGP
C.Full vs incremental routing updates
D.Only one is distance vector
C
Where one sends periodic updates of its entire routing information base, the other sends a full update when it first establishes contact with a neighbor, and afterward, only sends updates when there is a topology change.
Both the Enhanced Interior Gateway Routing Protocol (EIGRP) and Routing Information Protocol (RIP) are fairly simple.
Both EIGRP and RIP are Interior Gateway Protocols (IGP) which identify routes within an autonomous system (AS).
Both EIGRP and RIP are distance vector types, although EIGRP is a hybrid distance vector. The two default elements are bandwidth and delay.
A network architect is evaluating the algorithms used by routing protocols to build and update routing information bases. Which of the following algorithms are commonly used by routing protocols? (Select all that apply.)
A.Convergence
B.Prefix discovery
C.Distance vector
D.Link state
C, D
Distance vector protocols determine the best path to a destination based on the number of hops. They use metrics to build and update the routing information base (RIB). Examples include RIP (Routing Information Protocol).
Link state protocols build a network topology to determine the best path using metrics to construct and maintain the RIB by evaluating factors like bandwidth, cost, and delay.
Convergence is the process where routers agree on the network topology. It is not an algorithm for the RIB but rather describes how quickly a network adapts to changes.
Prefix discovery helps a host find network prefixes for next-hop determination. It is not an algorithm for the RIB.
