Cisco 300-101 Free Practice Questions

Answer: B 

Explanation: 

Answer: A 

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.

Reference: http://en.wikipedia.org/wiki/TCP_global_synchronization

Answer: A,C,E 

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/UDPdominance

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 UDPbased

flows, but it is beneficial to be aware of this behavior when making such application-mixing

decisions. Reference: http://www.cisco.com/warp/public/cc/so/neso/vpn/vpnsp/spqsd_wp.htm

Answer: A,C 

Explanation: 

Answer: A 

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. Reference: http://

www.cisco.com/web/strategy/docs/gov/IPV6at_a_glance_c45-625859.pdf

Answer: B 

Explanation: 

Router Advertisements (RA) are sent in response to router solicitation messages. Router

solicitation messages, which have a value of 133 in the Type field of the ICMP packet header, are sent by

hosts at system startup so that the host can immediately autoconfigure without needing to wait for the next

scheduled RA message. Given that router solicitation messages are usually sent by hosts at system

startup (the host does not have a configured unicast address), the source address in router solicitation

messages is usually the unspecified IPv6 address (0:0:0:0:0:0:0:0). If the host has a configured unicast

address, the unicast address of the interface sending the router solicitation message is used as the source

address in the message. The destination address in router solicitation messages is the all-routers multicast

address with a scope of the link. When an RA is sent in response to a router solicitation, the destination

address in the RA message is the unicast address of the source of the router solicitation message. RA

messages typically include the following information:

One or more onlink IPv6 prefixes that nodes on the local link can use to automatically configure their IPv6

addresses

Lifetime information for each prefix included in the advertisement

Sets of flags that indicate the type of autoconfiguration (stateless or stateful) that can be completed

Default router information (whether the router sending the advertisement should be used as a default

router and, if so, the amount of time (in seconds) the router should be used as a default router)

Additional information for hosts, such as the hop limit and MTU a host should use in packets that it

originates Reference: http://www.cisco.com/c/en/us/td/docs/ios/ipv6/configuration/guide/12_4t/

ipv6_12_4t_book/ip6- addrg_bsc_con.html

Answer: A 

Explanation: 

Network administrators can use Unicast Reverse Path Forwarding (Unicast RPF) to help limit

the malicious traffic on an enterprise network. This security feature works by enabling a router to verify the

reachability of the source address in packets being forwarded. This capability can limit the appearance of

spoofed addresses on a network. If the source IP address is not valid, the packet is discarded. Unicast

RPF works in one of three different modes: strict mode, loose mode, or VRF mode. Note that not all

network devices support all three modes of operation. Unicast RPF in VRF mode will not be covered in this

document. When administrators use Unicast RPF in strict mode, the packet must be received on the

interface that the router would use to forward the return packet. Unicast RPF configured in strict mode may

drop legitimate traffic that is received on an interface that was not the router's choice for sending return

traffic. Dropping this legitimate traffic could occur when asymmetric routing paths are present in the

network. When administrators use Unicast RPF in loose mode, the source address must appear in the

routing table. Administrators can change this behavior using the allow-default option, which allows the use

of the default route in the source verification process. Additionally, a packet that contains a source address

for which the return route points to the Null 0 interface will be dropped. An access list may also be

specified that permits or denies certain source addresses in Unicast RPF loose mode. Care must be taken

to ensure that the appropriate Unicast RPF mode (loose or strict) is configured during the deployment of

this feature because it can drop legitimate traffic. Although asymmetric traffic flows may be of concern

when deploying this feature, Unicast RPF loose mode is a scalable option for networks that contain

asymmetric routing paths. Reference: http://www.cisco.com/web/about/security/intelligence/unicastrpf.

html

Answer: B 

Explanation: 

Autoconfiguration is performed on multicast-enabled links only and begins when a multicastenabled

interface is enabled (during system startup or manually). Nodes (both, hosts and routers) begin

the process by generating a link-local address for the interface. It is formed by appending the interface

identifier to well-known link-local prefix FE80 :: 0. The interface identifier replaces the right-most zeroes of

the link-local prefix. Before the link-local address can be assigned to the interface, the node performs the

Duplicate Address Detection mechanism to see if any other node is using the same link-local address on

the link. It does this by sending a Neighbor Solicitation message with target address as the "tentative"

address and destination address as the solicited-node multicast address corresponding to this tentative

address. If a node responds with a Neighbor Advertisement message with tentative address as the target

address, the address is a duplicate address and must not be used. Hence, manual configuration is

required. Once the node verifies that its tentative address is unique on the link, it assigns that link-local

address to the interface. At this stage, it has IP-connectivity to other neighbors on this link. The

autoconfiguration on the routers stop at this stage, further tasks are performed only by the hosts. The

routers will need manual configuration (or stateful configuration) to receive site-local or global addresses.

The next phase involves obtaining Router Advertisements from routers if any routers are present on the

link. If no routers are present, a stateful configuration is required. If routers are present, the Router

Advertisements notify what sort of configurations the hosts need to do and the hosts receive a global

unicast IPv6 address. Reference: https://sites.google.com/site/amitsciscozone/home/important-tips/ipv6/

ipv6-stateless- autoconfiguration

Answer: A 

Explanation: 

To set the secure HTTP (HTTPS) server port number for listening, use the ip http secure-port

command in global configuration mode. To return the HTTPS server port number to the default, use the no

form of this command. ip http secure-port port-number no ip http secure-port Syntax Description port-

Integer in the range of 0 to 65535 is accepted, but the port number must be number higher than 1024

unless the default is used. The default is 443. Reference: http://www.cisco.com/en/US/docs/ios-xml/ios/

https/command/nm-https-cr-cl- sh.html#wp3612805529

Answer: A 

Explanation: 

Answer: A 

Explanation: 

Explanation: Extended Unique Identifier (EUI), as per RFC2373, allows a host to assign iteslf a unique 64-

Bit IP Version 6 interface identifier (EUI-64). This feature is a key benefit over IPv4 as it eliminates the

need of manual configuration or DHCP as in the world of IPv4. The IPv6 EUI-64 format address is obtained

through the 48-bit MAC address. The Mac address is first separated into two 24-bits, with one being OUI

(Organizationally Unique Identifier) and the other being NIC specific. The 16-bit 0xFFFE is then inserted

between these two 24-bits to for the 64-bit EUI address. IEEE has chosen FFFE as a reserved value which

can only appear in EUI-64 generated from the EUI-48 MAC address. Here is an example showing how the

Mac Address is used to generate EUI.

Next, the seventh bit from the left, or the universal/local (U/L) bit, needs to be inverted. This bit identifies

whether this interface identifier is universally or locally administered. If 0, the address is locally

administered and if 1, the address is globally unique. It is worth noticing that in the OUI portion, the globally

unique addresses assigned by the IEEE has always been set to 0 whereas the locally created addresses

has 1 configured. Therefore, when the bit is inverted, it maintains its original scope (global unique address

is still global unique and vice versa). The reason for inverting can be found in RFC4291 section 2.5.1.

Reference: https:// supportforums.cisco.com/document/100566/understanding-ipv6-eui-64-bit- address

Answer: A 

Explanation: 

Answer: A 

Explanation: 

The NTP service can be activated by entering any ntp command. When you use the ntp broadcast client

command, the NTP service is activated (if it has not already been activated) and the device is configured to receive NTP broadcast packets on a specified interface simultaneously.

Command Description

ntp broadcast Allows the system to receive NTP broadcast packets on an client interface.

Reference: http://www.cisco.com/c/en/us/td/docs/ios-xml/ios/bsm/command/bsm-xe-3se-3850- cr-book/

bsm-xe-3se-3850-cr-book_chapter_00.html

Answer: C 

Explanation: 

Logging-enabled access control lists (ACLs) provide insight into traffic as it traverses the

network or is dropped by network devices. Unfortunately, ACL logging can be CPU intensive and can

negatively affect other functions of the network device. There are two primary factors that contribute to the

CPU load increase from ACL logging: process switching of packets that match log-enabled access control

entries (ACEs) and the generation and transmission of log messages. Reference: http://www.cisco.com/

web/about/security/intelligence/acl-logging.html#4

Answer: First we need to find out 5 parameters (Bandwidth, Delay, Reliability, Load, MTU) of the s0/0/0 interface (the interface of R2 connected to R4) for redistribution: 

R2#show interface s0/0/0 

Write down these 5 parameters, notice that we have to divide the Delay by 10 because the metric unit is in tens of microsecond. For example, we get Bandwidth=1544 Kbit, Delay=20000 us, Reliability=255, Load=1, MTU=1500 bytes then we would redistribute as follows: 

R2#config terminal 

R2(config)# router ospf 1 

R2(config-router)# redistribute eigrp 100 metric-type 1 subnets 

R2(config-router)#exit 

R2(config-router)#router eigrp 100 

R2(config-router)#redistribute ospf 1 metric 1544 2000 255 1 1500 

Note: In fact, these parameters are just used for reference and we can use other parameters with 

no problem. 

If the delay is 20000us then we need to divide it by 10, that is 20000 / 10 = 2000) 

For R3 we use the show interface fa0/0 to get 5 parameters too 

R3#show interface fa0/0 

For example we get Bandwidth=10000 Kbit, Delay=1000 us, Reliability=255, Load=1, MTU=1500 bytes 

R3#config terminal 

R3(config)#router ospf 1 

R3(config-router)#redistribute eigrp 100 metric-type 1 subnets 

R3(config)#exit 

R3(config-router)#router eigrp 100 

R3(config-router)#redistribute ospf 1 metric 10000 100 255 1 1500 

Finally you should try to “show ip route” to see the 172.16.100.1 network (the network behind R4) 

in the routing table of R1 and make a ping from R1 to this network. 

Note: If the link between R2 and R3 is FastEthernet link, we must put the command below under 

EIGRP process to make traffic from R1 to go through R3 (R1 -> R2 -> R3 -> R4), which is better 

than R1 -> R2 -> R4. 

R2(config-router)# distance eigrp 90 105 

This command sets the Administrative Distance of all EIGRP internal routes to 90 and all EIGRP external routes to 105, which is smaller than the Administrative Distance of OSPF (110) -> the link between R2 & R3 will be preferred to the serial link between R2 & R4. Note: The actual OPSF and EIGRP process numbers may change in the actual exam so be sure to use the actual correct values, but the overall solution is the same. 

Answer: B 

Explanation: 

With prefix lists, the ge 24 term means greater than or equal to a /24 and the le 24 means less than or

equal to /24, so only a /24 is both greater than or equal to 24 and less than or equal to 24. This translate to any prefix in the 10.8.x.0/24 network, where X is any value in the 0-255 range.

Only the choice of 10.8.0.0.24 matches this.