Ch 6: IP Routing Essentials Flashcards
Which of the following routing protocols is classified as an EGP?
a. RIP
b. EIGRP
c. OSPF
d. IS-IS
e. BGP
E. BGP is the only Exterior Gateway Protocol listed here.
Which of the following routing protocols are classified as IGPs? (Choose all that apply.)
a. RIP
b. EIGRP
c. OSPF
d. IS-IS
e. BGP
A, B, C, and D. RIP, EIGRP, OSPF, and IS-IS are all classified as Interior Gateway Protocols.
A path vector routing protocol finds the best loop-free path by using ______.
- hop count
- bandwidth
- delay
- interface cost
- path attributes
- BGP is a path vector routing protocol that selects the best path based on path attributes such as MED, local preference, and AS_PATH length.
A distance vector routing protocol finds the best loop-free path by using ______.
- hop count
- bandwidth
- delay
- interface cost
- path attributes
- Distance vector protocols, such as RIP, only use hop count to select the best path.
A link-state routing protocol finds the best loop free path by using ______.
- hop count
- bandwidth
- delay
- interface cost
- path attributes
- Link-state routing protocols use the interface cost as the metric for Shortest Path First (SPF) calculations.
A router uses _________ as the first criterion for forwarding packets.
- path metric
- administrative distance
- longest match
- hop count
- The Cisco CEF sorts all network prefixes from shortest match to longest match for programming of the FIB. The path with the longest match is more explicit than a generic path.
A router uses _________ as the second criterion for forwarding packets.
- path metric
- administrative distance
- longest match
- hop count
- When two different routing protocols attempt to install the same route into the RIB, the route with the lowest AD is installed into the RIB.
The ability to install multiple paths from the same routing protocol with the same path metric into the RIB is known as ______.
- per-packet load balancing
- round-robin load balancing
- equal-cost multipathing
- parallel link forwarding
- Equal-cost multipath is the installation of multiple paths (that are deemed the best path) into the RIB when they come from the same routing protocol.
Which static route should be used to avoid unintentional forwarding paths with an Ethernet link failure?
- A directly attached static route
- A recursive static route
- A fully specified static route
- A static null route
- Ethernet links should not use a directly attached static route, and a link failure could result in the resolution of the next-hop IP address resolving to an unintentional link. The fully specified static route ensures that the next hop is resolvable using only the specified interface.
Virtual routing and forwarding (VRF) is useful with _____ addresses.
- MAC
- IPv4
- IPv6
- IPv4 and IPv6
- VRFs support multiprotocol (IPv4 and IPv6) addressing.
T/F: BGP can function as both an IGP and and EGP
BGP is an EGP protocol but can also be used within an autonomous system. If BGP exchanges routes within an autonomous system, it is known as an interior BGP (iBGP) session. If it exchanges routes between different autonomous systems, it is known as an exterior BGP (eBGP) session.
T/F: A distance vector protocol selects paths purely based on distance
T: A distance vector protocol selects paths purely based on distance. It does not account for link speeds or other factors.
Which of the following is not correct about EIGRP?
- It offers rapid convergence time for changes in the network topology.
- It sends periodic full routing table updates like DV protocols
- It uses hellos and forms neighbor relationships just as link-state protocols do.
- It uses bandwidth, delay, reliability, load, and maximum transmission unit (MTU) size instead of hop count for path calculations.
- It has the option to load balance traffic across equal- or unequal-cost paths.
The diffusing update algorithm (DUAL) is an enhanced distance vector algorithm that EIGRP uses to calculate the shortest path to a destination within a network. EIGRP advertises network information to its neighbors as other distance vector protocols do, but it has some enhancements, as its name suggests. The following are some of the enhancements introduced into this algorithm compared to other distance vector algorithms:
- It offers rapid convergence time for changes in the network topology.
- It sends updates only when there is a change in the network. It does not send full routing table updates in a periodic fashion, as distance vector protocols do.
- It uses hellos and forms neighbor relationships just as link-state protocols do.
- It uses bandwidth, delay, reliability, load, and maximum transmission unit (MTU) size instead of hop count for path calculations.
- It has the option to load balance traffic across equal- or unequal-cost paths.
T/F: A link-state dynamic IP routing protocol advertises the link state and link metric for each of its connected links only to every directly connected neighbor router in it’s AS.
False.
A link-state dynamic IP routing protocol advertises the link state and link metric for each of its connected links and directly connected routers to every router in the network.
OSPF advertisements are called link-state advertisements (LSAs), and IS-IS uses link-state packets (LSPs) for its advertisements.
What is the LSDB?
As a router receives an advertisement from a neighbor, it stores the information in a local database called the link-state database (LSDB) and advertises the link-state information on to each of its neighbor routers exactly as it was received.
The link-state information is essentially flooded throughout the network, unchanged, from router to router, just as the originating router advertised it. This allows all the routers in the network to have a synchronized and identical map of the network.
What is the Dijkstra algorithm?
Using the complete map of the network, every router in the network then runs the Dijkstra shortest path first (SPF) algorithm to calculate the best shortest loop-free paths. The link-state algorithm then populates the routing table with this information.
T/F: In addition to using less memory and CPU, distance vector protocols are less prone to routing loops than link state protocols.
Due to having the complete map of the network, link-state protocols usually require more CPU and memory than distance vector protocols, but they are less prone to routing loops and make better path decisions.