QUESTION 1 Of the following which can be identified as valid host IP addresses on the Internet? (Choose all that apply.)

A. 235.1.1.1

B. 223.20.1.1

C. 10.100.1.1

D. 127.0.0.1

E. 24.15.1.1 Answer: B, E Explanation: When you create an internal network, we recommend you use one of the following address groups reserved by the Network Working Group (RFC 1918) for private network addressing: Class A: 10.0.0.0 to 10.255.255.255 Class B: 172.16.0.0 to 172.31.255.255 Class C: 192.168.0.0 to 192.168.255.255 class D address start with the 1110 bit so the 223.20.1.1 is a legal class C address

QUESTION 2 What would be the consequence that all the other nodes would experience when a jam signal causes a collision on an Ethernet LAN?

A. All other nodes will recognize the collision and all nodes should stop sending new data.

B. All other nodes will compute part of a hash algorithm to determine the random amount of time the nodes should back off before retransmitting.

C. A signal was generated to help the network administrators isolate the fault domain between two Ethernet nodes.

D. A faulty transceiver is locked in the transmit state, causing it to violate CSMA/CD rules.

E. A high-rate of collisions was caused by a missing or faulty terminator on a coaxial Ethernet network. Answer: A Explanation: When a collision is detected the device will "transmit a jam signal" this will inform all the devices on the network that there has been a collision and hence stop them initiating the transmission of new data. This "jam signal" is a sequence of 32 bits that can have any value as long as it does not equal the CRC value in the damaged frame's FCS field. This jam signal is normally 32 1's as this only leaves a 1 in 2^32 chance that the CRC is correct by chance. Because the CRC value is incorrect all devices listening on the network will detect that a collision has occurred and hence will not create further collisions by transmitting immediately. "Part of a hash algorithm was computed, to determine the random amount of time the nodes should back off before retransmitting." WOULD SEEM CORRECT BUT IT IS NOT After transmitting the jam signal the two nodes involved in the collision use an algorithm called the "truncated BEB (truncated binary exponential back off)" to determine when they will next retransmit. The algorithm works as follows: Each device will wait a multiple of 51.2us (minimum time required for signal to traverse network) before retransmitting. 51.2us is known as a "slot". The device will wait a certain number of these time slots before attempting to retransmit. The number of time slots is chosen from the set {0,.....,2^k-1} at random where k= number of collisions. This means k is initialized to 1and hence on the first attempt k will be chosen at random from the set {0,1} then on the second attempt the set will be {0,1,2,3} and so on. K will stay at the value 10 in the 11, 12, 13, 14, 15 and 16th attempt but on the 17th attempt the MAC unit stops trying to transmit and reports an error to the layer above.

QUESTION 3 Which of the following statements regarding TACACS+ is valid? (Choose all that apply.)

A. Whenever more than one TACACS+ server is configured and the first one does not respond within a given timeout period, the next TACACS+ server in the list will be contacted.

B. If a key is used at both ends, the TACACS+ server's connection to the NAS encrypts the entire packet.

C. UDP must be used by the TACACS+ server for its connection to the NAS.

D. TCP or UDP for the NAS connection must be configured on the TACACS+ server.

E. TCP must be used by the TACACS+ server for its connection to the NAS. Answer: A, B, E Explanation: PIX Firewall permits the following TCP literal names: bgp, chargen, cmd, daytime, discard, domain, echo, exec, finger, ftp, ftp-data, gopher, h323, hostname, http, ident, irc, klogin, kshell, lpd, nntp, pop2, pop3, pptp, rpc, smtp, sqlnet, sunrpc, TACACS, talk, telnet, time, uucp, whois, and www. To specify a TACACS host, use the tacacs-server host global configuration command. Use the no form of this command to delete the specified name or address. timeout= (Optional) Specify a timeout value. This overrides the global timeout value set with the tacacs-server timeout command for this server only. tacacs-server key To set the authentication encryption key used for all TACACS+ communications between the access server and the TACACS+ daemon, use the tacacs-server key global configuration command. Use the no form of this command to disable the key. key = Key used to set authentication and encryption. This key must match the key used on the TACACS+ daemon.

QUESTION 4 The Cisco Sources Network Administrator is trying to configure IPSec with a remote system. When a tunnel is initiated from the remote end, the security associations (SAs) come up without errors. However, the administrator received a report that encrypted traffic is never successfully sent between the two endpoints. What is a possible cause?

A. NAT could be running between the two IPSec endpoints.

B. A mismatched transform set between the two IPSec endpoints.

C. There is a NAT overload running between the two IPSec endpoints.

D. Mismatched IPSec proxy between the two IPSec endpoints. Answer: C Explanation: This configuration will not work with port address translation (PAT). Note: NAT is a one-to-one-address translation, not to be confused with PAT, which is a many (inside the firewall)-to-one translation. IPSec with PAT may not work properly because the outside tunnel endpoint device cannot handle multiple tunnels from one IP address. You will need to contact your vendor to determine if the tunnel endpoint devices will work with PAT Question- What is PAT, or NAT overloading? Answer- PAT, or NAT overloading, is a feature of Cisco IOS NAT and can be used to translate internal (inside local) private addresses to one or more outside (inside global-usually registered) IP addresses. Unique source port numbers on each translation are used to distinguish between the conversations. With NAT overload, a translation table entry containing full address and source port information is created.

QUESTION 5 The newly appointed Cisco Sources trainee technician want to know which of the following represents the principles of a one way hash function. What will your reply be? (Choose all that apply.)

A. A fixed length output is created from a variable length input by a hash function.

B. A hash function cannot be random and the receiver cannot decode the hash.

C. A hash function is usually operated in an IPSec environment to provide a fingerprint for a packet.

D. A hash function must be easily decipherable by anyone who is listening to the exchange. Answer: A. C Explanation: Developers use a hash function on their code to compute a diges, which is also known as a one way hash .The hash function securely compresses code of arbitrary length into a fixed-length digest result.

QUESTION 6 Exhibit: How will IP traffic from the clients typically behave between the two Ethernet subnets?

A. Traffic between the Ethernet subnets on both routers will have to be decrypted.

B. NAT will translate the traffic between the Ethernet subnets on both routers.

C. Traffic will successfully access the Internet, though it will have to be decrypted between the router's Ethernet subnets.

D. Traffic will successfully access the Internet fully encrypted.

E. Traffic bound for the Internet will not be routed because the source IP addresses are private. Answer: C Explanation: NOT ENOUGH OF THE EXHIBIT TO MAKE A REAL CHOICE. THE EXHIBIT IS ONE OF IPSEC TAKE YOUR BEST SHOT.

QUESTION 7 What happens when one experiences a ping of death?

A. This is when an IP datagram is received with the "protocol" field in the IP header set to 1 (ICMP) and the "type" field in the ICMP header is set to 18 (Address Mask Reply).

B. This is when an IP datagram is received with the "protocol" field in the IP header set to 1 (ICMP), the Last Fragment bit is set, and (IP offset ' 8) + (IP data length) >65535. In other words, the IP offset (which represents the starting position of this fragment in the original packet, and which is in 8-byte units) plus the rest of the packet is greater than the maximum size for an IP packet.

C. This is when an IP datagram is received with the "protocol" field in the IP header set to 1 (ICMP) and the source equal to destination address.

D. This is when an the IP header is set to 1 (ICMP) and the "type" field in the ICMP header is set to 5 (Redirect). Answer: B Explanation: "A hacker can send an IP packet to a vulnerable machine such that the last fragment contains an offest where (IP offset *8) + (IP data length)>65535. This means that when the packet is reassembled, its total length is larger than the legal limit, causing buffer overruns in the machine's OS (because the buffer sizes are defined only to accommodate the maximum allowed size of the packet based on RFC 791)...IDS can generally recognize such attacks by looking for packet fragments that have the IP header's protocol field set to 1 (ICMP), the last bit set, and (IP offset *8) +(IP data length)>65535" CCIE Professional Development Network Security Principles and Practices by Saadat Malik pg 414 "Ping of Death" attacks cause systems to react in an unpredictable fashion when receiving oversized IP packets. TCP/IP allows for a maximum packet size of up to 65536 octets (1 octet = 8 bits of data), containing a minimum of 20 octets of IP header information and zero or more octets of optional information, with the rest of the packet being data. Ping of Death attacks can cause crashing, freezing, and rebooting.

QUESTION 8 What is the rationale behind a Network Administrator wanting to use Certificate Revocation Lists (CRLs) in their IPSec implementations?

A. CRLs allow netwotk administrators the ability to do "on the fly" authentication of revoked certificates.

B. They help to keep a record of valid certificates that have been issued in their network.

C. CRLs allow network administrators to deny devices with certain certificates from being authenticated to their network.

D. Wildcard keys are much more efficient and secure. CRLs should only be used as a last resort. Answer: C Explanation: A method of certificate revocation. A CRL is a time-stamped list identifying revoked certificates, which is signed by a CA and made available to the participating IPSec peers on a regular periodic basis (for example, hourly, daily, or weekly). Each revoked certificate is identified in a CRL by its certificate serial number. When a participating peer device uses a certificate, that system not only checks the certificate signature and validity but also acquires a most recently issued CRL and checks that the certificate serial number is not on that CRL.

QUESTION 9 What happens during a SYN flood attack?

A. TCP connection requests floods a target machine is flooded with randomized source address & ports for the TCP ports.

B. A TCP SYN packet, which is a connection initiation, is sent to a target machine, giving the target host's address as both source and destination, and is using the same port on the target host as both source and destination.

C. A TCP packet is received with the FIN bit set but with no ACK bit set in the flags field.

D. A TCP packet is received with both the SYN and the FIN bits set in the flags field. Answer: A Explanation: to a server that requires an exchange of a sequence of messages. The client system begins by sending a SYN message to the server. The server then acknowledges the SYN message by sending a SYNACK message to the client. The client then finishes establishing the connection by responding with an ACK message and then data can be exchanged. At the point where the server system has sent an acknowledgment(SYN-ACK) back to client but has not yet received the ACK message, there is a half-open connection. A data structure describing all pending connections is in memory of the server that can be made to overflow by intentionally creating too many partially open connections. Another common attack is the SYN flood, in which a target machine is flooded with TCP connection requests. The source addresses and source TCP ports of the connection request packets are randomized; the purpose is to force the target host to maintain state information for many connections that will never be completed. SYN flood attacks are usually noticed because the target host (frequently an HTTP or SMTP server) becomes extremely slow, crashes, or hangs. It's also possible for the traffic returned from the target host to cause trouble on routers; because this return traffic goes to the randomized source addresses of the original packets, it lacks the locality properties of "real" IP traffic, and may overflow route caches. On Cisco routers, this problem often manifests itself in the router running out of memory

QUESTION 10 The Cisco Secure Intrusion Detection System sensor does not have the following type of interface available:

A. Ethernet

B. Serial

C. Token Ring

D. FDDI Answer: B Explanation: Sensors are optimized for specific data rates and are packaged in Ethernet, Fast Ethernet (100BaseT), Token Ring, and FDDI configurations