The Secret of Cisco 200-105 exam question

Answer: E 

Explanation: 

What Is Administrative Distance? http://www.cisco.com/en/US/tech/tk365/technologies_tech_note09186a0080094195.shtml 

Select the Best Path Administrative distance is the first criterion that a router uses to determine which routing protocol to use if two protocols provide route information for the same destination. Administrative distance is a measure of the trustworthiness of the source of the routing information. Administrative distance has only local significance, and is not advertised in routing updates. Note: The smaller the administrative distance value, the more reliable the protocol. For example, if a router receives a route to a certain network from both Open Shortest Path First (OSPF) (default administrative distance - 110) and Interior Gateway Routing Protocol (IGRP) (default administrative distance - 100), the router chooses IGRP because IGRP is more reliable. This means the router adds the IGRP version of the route to the routing table. 

Answer: C 

Explanation: 

http://www.cisco.com/en/US/tech/tk365/technologies_tech_note09186a0080093f07.shtml 

Feasible Successors A destination entry is moved from the topology table to the routing table when there is a feasible successor. All minimum cost paths to the destination form a set. From this set, the neighbors that have an advertised metric less than the current routing table metric are considered feasible successors. Feasible successors are viewed by a router as neighbors that are downstream with respect to the destination. These neighbors and the associated metrics are placed in the forwarding table. When a neighbor changes the metric it has been advertising or a topology change occurs in the network, the set of feasible successors may have to be re-evaluated. However, this is not categorized as a route recomputation. Feasible successor is a route whose Advertised Distance (AD) is less than the Feasible Distance (FD) of the current best path. A feasible successor is a backup route, which is not stored in the routing table but, stored in the topology table. 

Answer: B,D,E 

Explanation: 

By default, all ports on a new switch belong to VLAN 1 (default & native VLAN). There are also some well-known VLANs (for example: VLAN 1002 for fddi-default; VLAN 1003 for token-ring…) configured by default -> A is not correct. To communicate between two different VLANs we need to use a Layer 3 device like router or Layer 3 switch -> B is correct. VLANs don’t affect the number of collision domains, they are the same -> C is not correct. Typically, VLANs increase the number of broadcast domains.We must use a different network (or sub-network) for each VLAN. For example we can use 192.168.1.0/24 for VLAN 1, 192.168.2.0/24 for VLAN 2 -> D is correct. A switch maintains a separate bridging table for each VLAN so that it can send frame to 

ports on the same VLAN only. For example, if a PC in VLAN 2 sends a frame then the 

switch look-ups its bridging table and only sends frame out of its ports which belong to 

VLAN 2 (it also sends this frame on trunk ports) -> E is correct. 

We can use multiple switches to expand VLAN -> F is not correct. 

Answer: B 

Explanation: 

To be the feasible successor, the Advertised Distance (AD) of that route must be less than the Feasible Distance (FD) of the successor. From the output of the “show ip eigrp topology 

10.0.0.5 255.255.255.255 we learn that the FD of the successor is 41152000. Now we will mention about the answers, in the “Composite metric is (…/…)” statement the first parameter is the FD while the second parameter is the AD of that route. So we need to find out which route has the second parameter (AD) less than 41152000 -> only answer B satisfies this requirement with an AD of 128256. 

Reference: http://networklessons.com/eigrp/eigrp-neighbor-and-topology-table-explained/ 

Answer: D 

Explanation: 

VLANs are local to each switch's database, and VLAN information is not passed between switches without implementing VLAN Trunk Protocol (VTP). Trunks carry traffic from all VLANs to and from the switch by default but, can be configured to carry only specified VLAN traffic. Trunk links are required to pass VLAN information between switches. So Sw11 port should be trunk not access port. Additionally, there are no ports assigned to VLAN 1. 

Answer: A,C,E 

Explanation: 

From the output, we see that all ports are in Designated role (forwarding state) -> A and E 

are correct. 

The command “show spanning-tree vlan 30 only shows us information about VLAN 30. We 

don’t know how many VLAN exists in this switch -> B is not correct. 

The bridge priority of this switch is 24606 which is lower than the default value bridge 

priority 32768 -> C is correct. 

All three interfaces on this switch have the connection type “p2p”, which means Point-to-point environment – not a shared media -> D is not correct. 

The only thing we can specify is this switch is the root bridge for VLAN 3o but we can not 

guarantee it is also the root bridge for other VLANs -> F is not correct. 

Answer: C 

Explanation: 

First, the question asks what switch services the printers, so it can be Switch 3 or Switch 4 

which is connected directly to the Printers. 

Designated port is a port that is in the forwarding state. All ports of the root bridge are 

designated ports. 

Switch 3 and Switch 4 has same priority so it will see on lowest MAC address and here 

switch 3 has lowest MAC address. So switch 3 segment will play a Designated port role. 

By comparing the MAC address of Switch 3 and Switch 4 we found that the MAC of Switch 

3 is smaller. Therefore the interface connected to the Printers of Switch 3 will become 

designated interface and the interface of Switch 4 will be blocked. 

Answer: B,E 

Explanation: 

In the router ospf Command, the ranges from 1 to 65535 so o is an invalid number - B is correct but A is not correct. To configure OSPF, we need a wildcard in the “network” statement, not a subnet mask. We also need to assign an area to this process - E is correct. 

Answer: A 

Explanation: 

Example 3-1 displays OSPF with a process ID of 1 and places all interfaces configured with 

an IP address in area 0. The network command.network 0.0.0.0 255.255.255.255 area 0.dictates that you do not care (255.255.255.255) what the IP address is, but if an IP 

address is enabled on any interface, place it in area 0. 

Example 3-1.Configuring OSPF in a Single Area 

router ospf 1 network 0.0.0.0 255.255.255.255 area 0 Reference: http://www.ciscopress.com/articles/article.asp?p=26919&seqNum=3 

Answer: E 

Explanation: 

First, notice that the more-specific routes will always be favored over less-specific routes regardless of the administrative distance set for a protocol. In this case, because we use OSPF for three networks (172.16.100.0 0.0.0.3, 172.16.100.64 0.0.0.63, 172.16.100.128 0.0.0.31) so the packets destined for these networks will not be affected by the default route. The default route configured on R1 "ip route 0.0.0.0 0.0.0.0 serial0/0 will send any packet whose destination network is not referenced in the routing table of router R1 to R2, it doesn't drop anything so answers A, B and C are not correct. D is not correct too because these routes are declared in R1 and the question says that "OSPF has been correctly configured on router R2, so network directly connected to router R2 can communicate with those three subnetworks. As said above, the default route configured on R1 will send any packet destined for a network that is not referenced in its routing table to 

R2; R2 in turn sends it to R1 because it is the only way and a routing loop will occur.