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2006-06-20 17:24:46
1,An ISDN PRI controller for the ISDN T1 on one of the TestKing routers is configured as shown below:
congroller t1 1
channel-group 0 timeslot 1-6
channel-group 1 timeslot 7
channel-group 2 timeslot 8
channel-group 3 timeslot 9-11
pri-group timeslot 12-24
What is the true about the partial configuration above?
answer:This is a correct configuration and a corresponding serial interface named interface serial 0:23 for the D channel will automatically be created
2,PPPoE
When a router wants to initiate a PPPoE session, it must first perform discovery to identify the Ethernet MAC address of the peering device and establish a PPPoE session_id. Discovery is inherently a client/server relationship. During Discovery, a router discovers the provider DSLAM. Discovery allows the CPE router to discover all available DSLAMs, and then select one. When discovery completes successfully, both the CPE router and the selected DSMAM have the information they will use to build their point-to-point connection over Ethernet
3,Which two statements are true when an IPSec-protected path is configured for transport mode?
answer: The payload of the packet is protected but the original IP address exposed
The application endpoints must also be the IPSec endpoints
IPSec can operate in one of two separate modes:transport mode and tunnel mode. These modes refer to how data is sent and secured throughout the network. In transport mode, IPSec protection is provided all the way from the source to the destination. In this way, transport mode is said to provide end-to-end transmission security.
Tunnel mode secures data only between tunnel points or gateways. Tunnel mode provides gateway-to-gateway transmission security. When data is in transmission between the client and the server, it remains unprotected until it reaches the gateway. Once at the gateway, it is secured with IPSec until it reaches the destination gateway. At this point,data packets are decrypted and verified. The data is then sent to the receiving host unprotected. Tunnel mode is often employed when data must leave the secure confines of a local LAN or WAN and travel between hosts over a public network such as the Internet.
Transport mode is a host-to-host connection involving only two machines. In tunnel mode, the IPSec machines act as gateways and traffic for any number of client machines may be carried.
4,Inside local address-The IP address assigned to a host on the inside network. This is the address configured as a parameter of the compter's OS or received via dynamic address allocation protocols such as DHCP. The address is likely ont a legitimate IP address assigned by the Network Information Center(NIC) or service provider
Inside global address-A legitimate IP address assigned by the NIC or service provider that represents one or more inside local IP addresses to the outside world
Outside local address-The IP address of an outside host as it appears to the inside network. Not necessarily a legitimate address, it is allocated from an address space routable on the inside
Outside global address-The IP address assigned to a host on the outside network by the host's owner. The address is allocated from a globally routable address or network space
5,A chat script is a one-line command that is used on an asynchronous interface to send commands for modem dialing and for logging on to remote systems. Chat scripts indicate the possible responses to expect and the information to send in each case. You can create a different chat script for each type of modem in use on the router and for each system the router might need to log in to.
6,Modem on Hold
V.92 Modem on Hold allows a dial-in customer to suspend a modem session to answer an incoming voice call or to place an outgoing call while engaged in a modem session. When the dial-in customer uses modem on hold to suspend an active modem session to engage in an incoming voice call, the Internet service provider(ISP) modem listems to the original modem connection and waits for the dial-in customer's modem to resume the connection. When the voice call ends, the modem signals the telephone system to end the second call and return to the original modem connection, then the modem signals the ISP modem that it is ready to resume the modem call. Both modems renegotiate the connection, and the original exchange of data continue
7,With a 25-pin connector(DB-25), only 8 pins are actually used for connecting a DTE to a DCE. The other 17 signals are not "interesting" and are ignored. The eight interesting signals can be grouped into three catagories by their functionality: data transfer, hardware flow control, and modem control. the figure shows the data transfer group, as follows:
TxD:Transmit data. The DTE transmits data to the DCE
RxD:Receive data. The DTE receives data from the DCE
GRD:ground. Provides the ground reference for voltage measurements
8,Modem control consists of several signals between the DTE and DCE that are used to initiate, terminate, and monitor the status of the connection. This figure shows the remaining two groups of interesting signals between a DTE device and a DCE device, as follows:
hardware flow control:
RTS:Request to send. The DTE has buffers available to receive from the DCE
CTS:clear to send. The DCE has buffers available to take data from the DTE
modem control:
DTR:data terminal ready. The DTE indicates to the DCE that it can accept an incoming call
CD:Carrier detect. The DCE has established a carrier signal with the remote DCE
DSR:data set ready. The DCE is ready for use. This pin is not used on modem connections
9,The lock DTE speed command, which might also be referred to as port rate adjust or buffered mode, is often related to the way in whch the modem handles error correction. This command varies widely from one modem to another.Locking the modem speed ensures that the modem always communicates with the Cisco access server or router at the speed configured on the Cisco auxiliary port. If this command is not used, the modem reverts to the speed of the data link, instead of communicating at the speed configured on the access server
10,What kind of terminals can you connect an ISDN line to?
answer: TE2/TA
TE1
Terminal equipment 1(TE1)-Designates a device that is compatible with the ISDN network. A TE1
connects to a network termination of either type 1 or type 2(NT1 or NT2)
for example:
digital telephone
router with ISDN interface
digital facsimile equipment
Terminal equipment 2(TE2)-Designates a device that is not compatible with ISDN and requires a terminal adapter
for example:
Terminals with X.21,Electronic industries association/Telecommunications industry association(EIA/TIA)-232, or X.25 interfaces
Router without ISDN interface (AGS+ and so on)
Terminal adapter(TA)-converts standard electrical signals into the form used by ISDN so that non-ISDN devices can connect to the ISDN network.
