Cisco Exam #640-801: CCNA (Transcender, set 2)
Test your basic networking knowledge for Cisco's entry-level certification exam with these nine questions and answers.
courtesy of Transcender
Question:
1. Which command is used at the DCE side of a serial link to set the clocking?
2. A host on your IP network has the IP address 15.208.209.85 and the subnet mask 255.255.240.0. What is the last possible valid host address on this subnet?
3. Which command do you use to view the current ISDN call information including the number called?
4. Which bridge does the spanning-tree algorithm select as the root bridge?
5. Which switching method requires a switch to copy each frame that it receives into its buffer, compute the CRC, and then discard frames containing errors, runt frames (fewer than 64 bytes) or giant frames (more than 1518 bytes)?
6. What are the two PPP authentication protocols?
7.
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Figure 1: Routing protocols for network
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Which routing protocols would you recommend using in the displayed network? (Choose two.)
a. IGRP
b. OSPF
c. RIPv1
d. EIGRP
8.
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Figure 2: Creating an access list
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You want to prevent FTP traffic from subnet 192.168.4.0 from reaching the 192.168.5.0 subnet but permit all other traffic. Which commands create an access list that could be applied as an output filter on the router's E0 interface to meet these specifications?
a. Router(config)#access-list 101 deny tcp 192.168.5.0 0.0.0.255 192.168.4.0 0.0.0.255 eq 20
Router(config)#access-list 101 deny tcp 192.168.5.0 0.0.0.255 192.168.4.0 0.0.0.255 eq 21
Router(config)#access-list 101 permit ip any any
b. Router(config)#access-list 101 deny 192.168.4.0 0.0.0.255 192.168.5.0 0.0.0.255 tcp eq 20
Router(config)#access-list 101 deny 192.168.4.0 0.0.0.255 192.168.5.0 0.0.0.255 tcp eq 21
Router(config)#access-list 101 permit ip any any
c. Router(config)#access-list 101 deny 192.168.5.0 0.0.0.255 192.168.4.0 0.0.0.255 tcp eq 20
Router(config)#access-list 101 deny 192.168.5.0 0.0.0.255 192.168.4.0 0.0.0.255 tcp eq 21
Router(config)#access-list 101 permit ip any any
d. Router(config)#access-list 101 deny tcp 192.168.4.0 0.0.0.255 192.168.5.0 0.0.0.255 eq 20
Router(config)#access-list 101 deny tcp 192.168.4.0 0.0.0.255 192.168.5.0 0.0.0.255 eq 21
Router(config)#access-list 101 permit ip any any
9. You have been assigned the 142.15.64.0 /24 network. You have decided to subnet this network into multiple subnets using a /29 subnet mask for all networks. Which addresses will be broadcast addresses using this new subnet mask? (Choose two.)
a. 142.15.64.24
b. 142.15.64.47
c. 142.15.64.64
d. 142.15.64.71
e. 142.15.64.83
1. clock rate
2. 15.208.223.254
3. show isdn active
The 'show isdn active' command displays the current call information, including the number called.
The 'show isdn status' command is used to display summary data on Layers 1 through 3. If Layer 1 is operating correctly, the status will be shown as active, and you know the problem is not due to a Layer 1 configuration.
The 'debug isdn q931' command displays the Layer 3 call setup and teardown.
The 'show interfaces bri0' command displays statistics for the BRI interface.
For more information see the Cisco document "ISDN Authentication and Callback with Caller ID."
4. the bridge with the lowest-value bridge identifier
The bridge with the lowest-value bridge identifier (Bridge ID) is selected as the root bridge. The bridge identifier is usually the bridge priority plus the MAC address of the bridge. There is a single root bridge elected per broadcast domain. All ports on the root bridge are in the forwarding state.
Bridges and switches use the Spanning Tree Protocol (STP) to prevent network loops. Without a loop-avoidance service on the network, Layer 2 devices will endlessly flood broadcasts. An STP-enabled device recognizes a loop in the topology and blocks one or more redundant paths, preventing the loop. STP is enabled by default on Catalyst switches, and allows the switches to continually explore the network so that the loss or addition of a switch or bridge or the existence of a loop is quickly discovered.
Root bridge selection is not random and does not depend on how many or how few ports a bridge or switch has. The bridge with the lowest-value Bridge ID is selected as the root bridge.
NOTE: The Bridge ID is composed of a two-byte priority and a six-byte MAC address. Since root selection is automatic, if you need a switch to be the root bridge, lower the priority of the switch.
For more information about STP on Catalyst 1900 switches, see the Release Notes for the Catalyst 1900 and Catalyst 2820 Series Switches, Version 9.00 documentation.
5. store-and-forward
With the store-and-forward switching method, a switch copies an entire frame to its buffer, computes the CRC, and discards frames containing errors, and runt (less than 64 bytes) or giant (more than 1518 bytes) frames.
6. PAP (Password Authentication Protocol) and CHAP (Challenge Handshake Authentication Protocol).
PAP requires a two-way handshake.
1. The password is sent by the remote node
2. The password is accepted or rejected
7. Answers B and D are correct. The OSPF and EIGRP routing protocols are classless routing protocols and will support the displayed network.
A classless routing protocol transports the network mask value with the identified network address to support networks that use more than one mask. The network displayed is using three different masks for the component networks. A 26-bit mask, or 255.255.255.192; a 28-bit mask, or 255.255.255.240; and a 30-bit mask, or 255.255.255.252 are all used when configuring the devices in the exhibit. Variable Length Subnet Masking (VLSM) enables you to make efficient use of the assigned address space. For example, a 30-bit mask is considered the most efficient mask for use on point-to-point WAN interfaces. A point-to-point WAN interface requires a maximum of two IP addresses. The 30-bit mask provides a maximum of two IP host addresses assigned in the subnet. Therefore, no host addresses are wasted.
For more information on the Subnetting and VLSM, go here.
8. Answer D is correct.
To create an access list that will block FTP traffic from network 192.168.4.0 that is destined for network 192.168.5.0 while allowing all other traffic, use the following series of commands:
- Router(config)#access-list 101 deny tcp 192.168.4.0 0.0.0.255 192.168.5.0 0.0.0.255 eq 20
This command blocks FTP control traffic from hosts 192.168.4.0 to 192.168.4.255 that is destined for network 192.168.5.0.
- Router(config)#access-list 101 deny tcp 192.168.4.0 0.0.0.255 192.168.5.0 0.0.0.255 eq 21
This command blocks FTP data traffic from any host on network 192.168.4.0 is destined for a host on network 192.168.5.0.
- Router(config)#access-list 101 permit ip any any
This command permits all IP traffic from any source host to any destination host that does not match the previously defined filters. It is necessary to add this command to the access list because there is an implicit "deny all" at the end of all access lists. Without this command, all traffic would be blocked.
These commands create the access list but the access list does not affect traffic until it is applied to an interface. The following commands apply the access list to Ethernet 0:
Router(config)#interface ethernet 0
Router(config-if)#ip access-group 101 out
The 'ip access-group 101 out' command applies access list 101 as an outbound interface to Ethernet 0.
For more information about access lists, see the Cisco documentation "Access Control Lists: Overview and Guidelines."
9. Answers B and D are correct.
The /29 subnet mask (255.255.255.248) uses the first five bits in the last octet for subnets. This means that each subnet will be a multiple of eight because the least significant bit in the subnet mask masks the 2^3 bit. Therefore, the subnets for 142.15.64.x /29 will be the following:
142.15.64.8
142.15.64.16
142.15.64.24
142.15.64.32
142.15.64.40
142.15.64.48
142.15.64.56
142.15.64.64
142.15.64.72
142.15.64.248
The broadcast address for each subnet is the last address in the subnet. To find the broadcast address for a subnet, simply subtract one from the next subnet. For example, the broadcast address for the 142.15.64.8 subnet is 142.15.64.15. Another way to think about this is that every multiple of eight minus one in the last octet is a broadcast address, up to 247.
For more information about subnetting, see Cisco's Tech Notes "IP Addressing and Subnetting for New Users."
Questions and answers provided by Transcender. To order the full version of this exam simulation, click here.
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