how many questions of 200-105 exam question?

Answer: A,B,F 

Explanation: 

The question says "no other configuration changes have been made" so we can 

understand these switches have the same bridge priority. SwitchC has lowest MAC 

address so, it will become root bridge and 2 of its ports (Fa0/1 & Fa0/2) will be designated 

ports (DP). Because SwitchC is the root bridge the 2 ports nearest SwitchC on SwitchA 

(Fa0/1) and SwitchD (Gi0/2) will be root ports (RP) -> B and F are correct. 

SwitchB must have a root port so which port will it choose? To answer this question we 

need to know about STP cost and port cost. 

In general, "cost" is calculated based on bandwidth of the link. The higher the bandwidth on 

a link, the lower the value of its cost. Below are the cost values you should memorize: 

Link speed Cost SwitchB will choose the interface with lower cost to the root bridge as the root port so we must calculate the cost on interface Gi0/1 & Gi0/2 of SwitchB to the root bridge. This can be calculated from the "cost to the root bridge" of each switch because a switch always advertises its cost to the root bridge in its BPDU. The receiving switch will add its local port cost value to the cost in the BPDU. SwitchC advertises its cost to the root bridge with a value of 0. Switch D adds 4 (the cost value of 1Gbps link) and advertises this value (4) to SwitchB. SwitchB adds another 4 and learns that it can reach SwitchC via Gi0/1 port with a total cost of 8. The same process happens for SwitchA and SwitchB learns that it can reach SwitchC via Gi0/2 with a total cost of 23 -> Switch B chooses Gi0/1 as its root port. Now our last task is to identify the port roles of the ports between SwitchA & SwitchB. It is rather easy as the MAC address of SwitchA is lower than that of SwitchB so Fa0/2 of SwitchA will be designated port while Gi0/2 of SwitchB will be alternative port. 

Answer: B 

Explanation: 

In order to be sufficiently versatile to be portable to a wide variety of environments, PPP provides a Link Control Protocol (LCP). The LCP is used to automatically agree upon the encapsulation format options, handle varying limits on sizes of packets, detect a looped-back link and other common misconfiguration errors, and terminate the link. Other optional facilities provided are authentication of the identity of its peer on the link, and determination when a link is functioning properly and when it is failing. 

Reference: Link Control Protocol 

http://www.ietf.org/rfc/rfc1661.txt 

Answer: B,D 

Explanation: 

IP split horizon checking is disabled by default for Frame Relay encapsulation to allow routing updates to go in and out of the same interface. An exception is the Enhanced Interior Gateway Routing Protocol (EIGRP) for which split horizon must be explicitly disabled. Certain protocols such as AppleTalk, transparent bridging, and Internetwork Packet Exchange (IPX) cannot be supported on partially meshed networks because they require split horizon to be enabled (a packet received on an interface cannot be transmitted over the same interface, even if the packet is received and transmitted on different virtual circuits). Configuring Frame Relay subinterfaces ensures that a single physical interface is treated as multiple virtual interfaces. This capability allows you to overcome split horizon rules so packets received on one virtual interface can be forwarded to another virtual interface, even if they are configured on the same physical interface. 

Answer: B,C 

Explanation: 

OSPF uses a LSDB (link state database) and fills this with LSAs (link state advertisement). The link types are as follows: 

LSA Type 1:. Router LSA  

LSA Type 2:.. . . . . . . .  Network LSA  

LSA Type 3:. Summary LSA  

LSA Type 4:. Summary ASBR LSA  

LSA Type 5:. Autonomous system external LSA  

LSA Type 6:. Multicast OSPF LSA  

LSA Type 7:. Not-so-stubby area LSA  

LSA Type 8:. External attribute LSA for BGP  

If all routers are in the same area, then many of these LSA types (Summary ASBR LSA, external LSA, etc) will not be used and will not be generated by any router. 

All areas in an Open Shortest Path First (OSPF) autonomous system must be physically connected to the backbone area (Area 0). In some cases, where this is not possible, you can use a virtual link to connect to the backbone through a non-backbone area. You can also use virtual links to connect two parts of a partitioned backbone through a non-backbone area. The area through which you configure the virtual link, known as a transit area, must have full routing information. The transit area cannot be a stub area. Virtual links are not ideal and should really only be used for temporary network solutions or migrations. However, if all locations are in a single OSPF area this is not needed. 

Answer: D 

Explanation: 

Two terms that appear often in the EIGRP world are "successor" and "feasible successor". A successor is the route with the best metric to reach a destination. That route is stored in the routing table. A feasible successor is a backup path to reach that same destination that can be used immediately if the successor route fails. These backup routes are stored in the topology table. 

Reference: http://study-ccna.com/eigrp-overview 

Answer: A,C 

Explanation: 

Link State Routing Protocols http://www.ciscopress.com/articles/article.asp?p=24090&seqNum=4 

Link state protocols, sometimes called shortest path first or distributed database protocols, are built around a well-known algorithm from graph theory, E. W. Dijkstra'a shortest path algorithm. Examples of link state routing protocols are: Open Shortest Path First (OSPF) for IP The ISO's Intermediate System to Intermediate System (IS-IS) for CLNS and IP DEC's DNA Phase V Novell's NetWare Link Services Protocol (NLSP) Although link state protocols are rightly considered more complex than distance vector protocols, the basic functionality is not complex at all: 

1. Each router establishes a relationship—an adjacency—with each of its neighbors. 

2. Each router sends link state advertisements (LSAs), some 

3. Each router stores a copy of all the LSAs it has seen in a database. If all works well, the databases in all routers should be identical. 

4. The completed topological database, also called the link state database, describes a graph of the internetwork. Using the Dijkstra algorithm, each router calculates the shortest path to each network and enters this information into the route table. 

Answer: C 

Explanation: 

CCNA Tutorial: The OSPF Router ID (RID) http://www.thebryantadvantage.com/CCNACertificationExamTutorialOSPFRouterIDRID.ht m 

When determining the Router ID (RID) of an OSPF-enabled router, OSPF will always use the numerically highest IP address on the router’s loopback interfaces, regardless of whether that loopback is OSPF-enabled. 

What if there is no loopback? OSPF will then use the numerically highest IP address of the physical interfaces, regardless of whether that interface is OSPF-enabled. 

Answer: C 

Explanation: 

From the routing table we learn that network 192.168.10.0/30 is learned via 2 equal- cost paths (192.168.10.9 &192.168.10.5) - traffic to this network will be load-balanced. 

Answer: C,E,F 

Explanation: 

EIGRP performs an auto-summarization each time it crosses a border between two different major networks, so when R2 advertises the routes to R4 it will advertise only the summarized routes of 10.0.0.0/8 and 172.16.0.0/16, along with the 192.168.1.0/24 route coming from R3. 

Answer: E 

Explanation: 

The command frame-relay map ip 10.121.16.8 102 broadcast means to map the remote IP 

10.121.16.8 to the local DLCI 102. When the “broadcast” keyword is included, it turns Frame Relay network as a broadcast network, which can forward broadcasts.