ITP4928 Tutorial 2

1.		Identify the following possible problems to the serial status lines.                   [2] (Each problem should appear once in your answer.) P1 -   Clock rate is not set P2 -   Shutdown interface command is included in configuration P3-  Cabling is faulty or incorrect P4 -  CSU/DSU hardware problem      P5 -   Router is misconfigured Status Line Problem Serial x is up, line protocol is down (disabled) P4 Serial x is up, line protocol is down (DCE mode) P1 Serial x is administratively down, line protocol is down P2 Serial x is down, line protocol is down P3 Serial x is up, line protocol is down (DTE mode) P5
		Given the following Cisco HDLC frame: Cisco HDLC Frame
		(i)  Why is protocol field added in the Cisco HDLC frame?                         [2]
		Cisco HDLC frame contains a protocol field to identifying the network protocol being encapsulated and solving the inability to provide multiprotocol support.
		(ii) What is the limitation of Cisco HDLC protocol when connecting routers?              [2]
		Cisco HDLC is proprietary and can be used to connect two Cisco routers.

2.	(a)	Briefly describe the function of LCP and NCP.                                      [2]
=		LCP is used to establish, configure, and test the data link connection. There are family of NCPs for establishing and configuring different network layer protocols.
	(b)	Determine whether each characteristic describe LCP or NCP.                        [3]
	(c)	For each characteristic, identify if it is associated with PAP or CHAP authentication.        [2] Characteristic Authentication Protocol Three-way handshake CHAP Password sent in plain text PAP Open to repeated trial-and-error attack PAP Periodic verification CHAP

	(d)	In the following figure, R1 should establish a PPP connection with R3 by using PAP authentication. Assume that R3 is having correct configurations. Complete the configuration of R1.                                                                      [4]
		Router R1 :         hostname R1         username  R3    password     cisco123          interface  s0/0         ip address 192.168.3.1  255.255.255.0         encapsulation      ppp                     _         ppp authentication pap  ppp pap sent-username R1 password cisco123
3.	(a)	Name the two types of Frame Relay address mapping methods.                       [2]
		Dynamic mapping and static mapping
	(b)	Briefly describe the function of Inverse Address Resolution Protocol (Inverse ARP).       [2]
		The Inverse Address Resolution Protocol (Inverse ARP) obtains Layer 3 addresses of other stations from Layer 2 addresses (DLCIs). It is used in Frame Relay dynamic mapping.
	(c)	Match the following LMI extensions to the correct descriptions.                       [4] VC status messages, Multicasting, Global addressing, Simple flow control Allows a sender to transmit a single frame that is delivered to multiple recipients. Multicasting Gives connection identifiers global rather than local significance. Global addressing Provide information about PVC integrity by communicating and synchronizing between devices. VC status messages Provides for an XON/XOFF flow control mechanism that applies to the entire Frame Relay interface. Simple flow control
	(d)	Match the Frame Relay Bandwidth and Flow Control terms to the descriptions.          [7] CIR, DE, FECN, BECN, Access Rate, Queuing, Bursting Term Frame Relay Bandwidth and Flow Control Description Access Rate Port bandwidth of the local loop. Bursting Bandwidth “borrowing” from other PVCs when available. Queuing Holding frame in a buffer before sending. CIR Guaranteed bandwidth for a specific PVC. FECN Downstream notification that there is congestion on a Frame Relay switch. BECN Upstream notification that there is congestion on a Frame Relay switch. DE Identifies the frame to be dropped in times of congestion.

4.		The network below shows 4 sites that are connected by Frame Relay WAN service and OSPF routing protocol is used for the sites. The virtual circuits between router A and router B are shown in dotted lines. And the virtual circuits between router C and router D are shown in solid lines.
	(a)	Comparing to dedicated leased lines. Briefly describe any TWO advantages of Frame Relay. [4]
		Any 2 of the followings, · Frame Relay reduces network costs by using less equipment, less complexity, and an easier implementation. · Provides greater bandwidth, reliability, and resiliency than private or leased lines. · With increasing globalization and the growth of one-to-many branch office topologies, Frame Relay offers simpler network architecture and lower cost of ownership.

	(b)	The DLCI 444 has been used on the link connected to router D. Can the same DLCI number – 444 can also be used on router C to set up a new circuit. Explain briefly.                [2]
		Yes. The same number 444 can be used again in router C. The reason is that the DLCIs only have local significance.
	(c)	By using the static frame relay address mapping (refer to the following mapping command), write down the static maps used on router A to connect router B. Assume that broadcast frames will be allowed to pass through.                                                                                                   [2] Static mapping command:                 frame-relay map protocol protocol-address dlci [broadcast]
		frame-relay map ip 188.10.65.3 222 broadcast
5.	(a)	What is the function of Network Address Translation (NAT)?                         [2]
		NAT translates private, internal addresses into public, external addresses.
	(b)	Briefly describe the following types of NAT methods.                               [6]
		(i)	Static NAT
			Uses a one-to-one mapping of local and global addresses, and these mappings remain constant.
		(ii)	Dynamic NAT
			Uses a pool of public addresses and assigns them on a first-come, first-served basis.
		(iii)	Port Address Translation (PAT)
			Port Address Translation (PAT) maps multiple private IPv4 addresses to a single public IPv4 address or a few addresses.
	(c)	Given that the private IP address of the server will always be translated to 209.200.200.8, complete the following static NAT configuration of R2                        [4]
		R2(config)#ip nat inside source static 192.168.10.254 209.200.200.8  [3] R2(config)#int s0/0/0 R2(config-if)#ip nat inside [0.5] R2(config-if)#int s0/1/0 R2(config-if)#ip nat outside [0.5]
	(d)	With the following requirements, complete the dynamic NAT configuration of R2:       [8] -  Pool name = NAT-POOL   o       Range: 209.165.100.240/29 -  Named standard ACL = NAT-INT o       LAN: 192.168.10.0/24 o       LAN: 192.168.11.0/24
		R2(config)# ip nat pool NAT-POOL 209.165.100.241 209.165.100.246 netmask 255.255.255.248     [3] R2(config)#ip access-list standard NAT-INT R2(config-std-nacl)#permit 192.168.10.0 0.0.0.255  [1] R2(config-std-nacl)#permit 192.168.11.0 0.0.0.255  [1] R2(config-std-nacl)#exit R2(config)#ip nat inside source list NAT-INT pool NAT-POOL   [2] R2(config)#interface serial 0/0/0 R2(config-if)#ip nat inside    [0.5] R2(config-if)#exit R2(config)#interface serial 0/0/1 R2(config-if)#ip nat outside   [0.5]