CEF is an optimized Layer 3 forwarding path through a router or switch. CEF optimizes routing table lookup by creating a special, easily searched tree structure based on the IP routing table. The forwarding Pass4itsure 300-101 dumps information is called the Forwarding Information Base (FIB), and the cached adjacency information is called the Adjacency Table.
Exam Code: 300-101
Exam Name: Implementing Cisco IP Routing (ROUTE v2.0)
Updated: May 14, 2017
Q&As: 247
A lot of sources on router architecture divides router functions into three operational planes:
- Management plane: is concerned with the management of the device. For example, an administrator connecting to a router through a Secure Shell (SSH) connection through one of the router’s VTY lines would be a management plane operation.
- Control plane: is concerned with making packet-forwarding decisions. For example, routing protocol operation would be a control plane function. (the brain of the network)
Pass4itsure 300-101 dumps Data plane: is concerned with the forwarding of data through a router (ASIC). For example, end-user traffic traveling from a user’s PC to a web server on a different network would go across the data plane. (means the hardware itself)
Cisco Exam 300-101 Dumps Blog Series
QUESTION 1
Refer to the exhibit.
Based on this FIB table, which statement is correct?
A. There is no default gateway.
B. The IP address of the router on FastEthernet is 209.168.201.1.
C. The gateway of last resort is 192.168.201.1.
D. The router will listen for all multicast traffic.
Correct Answer: C Explanation
Explanation/Reference:
Explanation:
The 0.0.0.0/0 route is the default route and is listed as the first CEF entry. Here we see the next hop for this default route lists 192.168.201.1 as the default router
(gateway of last resort).
QUESTION 2
Refer to the exhibit.
A network administrator checks this adjacency table on a router. What is a possible cause for the incomplete marking?
A. incomplete ARP information
B. incorrect ACL
C. dynamic routing protocol failure
D. serial link congestion Correct Answer: A
Explanation Explanation/Reference:
Explanation:
To display information about the Cisco Express Forwarding adjacency table or the hardware Layer 3-switching adjacency table, use the show adjacency
command.
Reasons for Incomplete Adjacencies
There are two known reasons for an incomplete adjacency:
The router cannot use ARP successfully for the next-hop interface.
After a clear ip arp or a clear adjacency command, the router marks the adjacency as incomplete. Then it fails to clear the entry.
In an MPLS environment, IP CEF should be enabeled for Label Switching. Interface level command ip route-cache cef No ARP Entry When CEF cannot locate a valid adjacency for a destination prefix, it punts the packets to the CPU for ARP resolution and, in turn, for completion of the adjacency.
Reference:
QUESTION 3
A network engineer notices that transmission rates of senders of TCP traffic sharply increase and decrease simultaneously during periods of congestion. Which condition causes this?
A. global synchronization
B. tail drop
C. random early detection
D. queue management algorithm
Correct Answer: A Explanation Explanation/Reference:
Explanation: TCP global synchronization in computer networks can happen to TCP/IP flows during periods of congestion because each sender will reduce their transmission rate at the same time when packet loss occurs. Routers on the Internet normally have packet queues, to allow them to hold packets when the network is busy, rather than discarding them. Because routers have limited resources, the size of these queues is also limited. The simplest technique to limit queue size is known as tail drop. The queue is allowed to fill to its maximum size, and then any new packets are simply discarded, until there is space in the queue again. This causes problems when used on TCP/IP routers handling multiple TCP streams, especially when bursty traffic is present. While the network is stable, the queue is constantly full, and there are no problems except that the full queue results in high latency. However, the introduction of a sudden burst of traffic may cause large numbers of established, steady streams to lose packets simultaneously.
QUESTION 4
Which three problems result from application mixing of UDP and TCP streams within a network with no QoS? (Choose three.)
A. starvation
B. jitter
C. latency
D. windowing
E. lower throughput
Correct Answer: ACE Explanation
Explanation/Reference:
Explanation: It is a general best practice not to mix TCP-based traffic with UDP-based traffic (especially streaming video) within a single service provider class due to the behaviors of these protocols during periods of congestion. Specifically, TCP transmitters will throttle-back flows when drops have been detected. Although some UDP applications have application-level windowing, flow control, and retransmission capabilities, most UDP transmitters are completely oblivious to drops and thus never lower transmission rates due to dropping. When TCP flows are combined with UDP flows in a single service provider class and the class experiences congestion, then TCP flows will continually lower their rates, potentially giving up their bandwidth to drop-oblivious UDP flows. This effect is called TCP-starvation/ UDP-dominance. This can increase latency and lower the overall throughput. TCP-starvation/UDP-dominance likely occurs if (TCP-based) mission-critical data is assigned to the same service provider class as (UDP-based) streaming video and the class experiences sustained congestion. Even if WRED is enabled on the service provider class, the same behavior would be observed, as WRED (for the most part) only affects TCP-based flows. Granted, it is not always possible to separate TCP-based flows from UDP-based flows, but it is beneficial to be aware of this behavior when making such application-mixing decisions.
QUESTION 5
Which method allows IPv4 and IPv6 to work together without requiring both to be used for a single connection during the migration process?
A. dual-stack method
B. 6to4 tunneling
C. GRE tunneling
D. NAT-PT
Correct Answer: A Explanation
Explanation/Reference:
Explanation:
Dual stack means that devices are able to run IPv4 and IPv6 in parallel. It allows hosts to simultaneously reach IPv4 and IPv6 content, so it offers a very flexible
coexistence strategy. For sessions that support IPv6, IPv6 is used on a dual stack endpoint. If both endpoints support IPv4 only, then IPv4 is used.
Benefits:
Native dual stack does not require any tunneling mechanisms on internal networks
Both IPv4 and IPv6 run independent of each other
Dual stack supports gradual migration of endpoints, networks, and applications.
There are some Pass4itsure 300-101 dumps reasons for you to consider implementing passive interfaces on your network. The best i can think of is security and to have control of which interfaces form adjacencies and send/receive routing updates, as implementing the command “passive-interface” won’t allow the propagation of routing updates but in some protocols it will allow receiving routing updates.
This is most useful Pass4itsure 300-101 dumps in edge routers connected to SP premises and distribution routers. Enabling routing indiscriminately on several or all interfaces may increase the chances for the insertion of unauthorized routing peers. Also, unnecessary routing protocol exchanges increase CPU overhead on the router.
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