1. What is the difference in the procedures for assigning hardware addresses and network addresses?
Hardware addresses usually are bound to network devices physical interfaces and assigned by a network equipment manufacturer. Network addresses are assigned by a network administrator and might be changed if necessary.
2. Which of the addresses listed here could be used as local addresses in the IP internetwork? Which addresses cannot be used this way?
A. A 6-byte MAC address, such as 12-В3-3В-51-А2-10 - correct
B. An X.25 address, such as 25012112654987 – could be used as a local address when X.25 network is a part of IP inter-network
C. A 12-byte IPX address, such as 13.34.В4.0А.С184.108.40.206.54.С5.3В.0 - could be used as a local address when IPX network is a part of IP inter-network
D. A VPI/VCI address of an ATM network. - could be used as a local address when ATM network is a part of IP inter-network
3. Which of these statements provided are always correct?
A. Every interface of every bridge or switch has a MAC address. – Always correct
B. Each bridge or switch has a network address. – Not always correct as a bridge or a switch doesn’t use network addresses for its primary operation – forwarding frames. However, network address could be used by a bridge or a switch for management operations, e.g. when they support SNMP management protocol.
C. Each interface of the bridge or switch has a network address. – The explanation for statement B is also applicable for this statement
D. Each router has a network address. – Not always correct as network addresses must be assigned to router interfaces but not to router itself. However, as for bridges and switches, a network address might be assigned to a router itself to support management operations.
E. Each interface of the router always has a MAC address. - Always correct
F. Each interface of a router has a network address. - Always correct
4. Which of the addresses provided here cannot be used as IP addresses of network interfaces for Internet hosts? For addresses that do not contain syntax error, determine the class: А, В, С, D, or E.
(A) 127.0.0.1 - It is the loopback address and it can’t be used as an address of a network interface of an Internet host
(B) 220.127.116.11 – It is a Class C address, it can be used as an address of a network interface of an Internet host
(C) 18.104.22.168 - It is a Class D address (multicast) , it can’t be used as an address of a network interface of an Internet host
(D) 22.214.171.124 - It is a Class A address, it can be used as an address of a network interface of an Internet host
(E) 10.234.17.25 - It is a Class A address, which belongs to 10.0.0.0 network; it is reserved for a private use and hence can’t be used as an address of a network interface of an Internet host
(F) 126.96.36.199 - It is a broadcast address for Class B networks, it can’t be used as an address of a network interface of an Internet host
(G) 188.8.131.52 - It is a Class A address, it can be used as an address of a network interface of an Internet host
(H) 184.108.40.206 - It is a Class C address, it can be used as an address of a network interface of an Internet host
((I) 193.256.1.16 - It is a syntactically incorrect address as a byte value can’t be bigger than 255
(J) 220.127.116.11 - It is a Class C address, it can be used as an address of a network interface of an Internet host
(K) 18.104.22.168 - It is a broadcast address for Class C networks, it can’t be used as an address of a network interface of an Internet host
(L) 22.214.171.1245 - It is a syntactically incorrect address as a byte value can’t be bigger than 255
5. Suppose that an IP address of some host of a subnet of 126.96.36.199; the mask value for this subnet is 255.255.255.240. Determine the subnet number. How many hosts may this subnet contain?
Subnet number is 188.8.131.52. 4 bits can be used for addressing the subnet hosts, which gives 16 possible values. As binary values 0000 and 1111 are reserved then the maximum number of hosts is 14.
6. Assume that you know the mapping between IP addresses and domain names for all computers in a network except one. For that computer, only the domain name is known. Provided with all this information, can you define its IP address with certainty?
In general case the answer is No as there is no any algorithmic dependence between IP addresses and domain names. However, if a network administrator used some particular dependence for assigning domain names and IP addresses, e.g. 184.108.40.206 address was given to a host with a domain name ws1.star.com; 195. 50.60.2 address was given to a host with a domain name ws2.star.com and so on – then in this case it would be possible.
7. How many ARP tables are there on a computer? How many are there on a router? And on a switch?
As ARP-table is built for each interface then a number of ARP tables corresponds to a number of device interfaces. If it is a 2-layer switch which doesn’t support IP, then it doesn’t have ARP tables at all.
8. Functionally, ARP can be divided into the client part and the server part. Describe the functions of the client and server parts.
9. Which addresses does an administrator enter into an ARP table? For what purpose?
To speed up a network operations.
10. In what cases is it useful to use Proxy-ARP?
For example, for remote nodes using dial-up connection.
11. Is it possible to determine from the domain names of computers how close they are to one another geographically?
No, it is not possible in general case.
12. Some computer has the IP address 220.127.116.11 and the domain name new.firm.net. Determine which, if any, of the following domain names belongs to another computer that has the IP address 18.104.22.168: new1.firm.net, new.firm1.net, or new.1firm.net.
It is not possible to determine; see comments to the question 6.
13. What are the common features of DNS and file system?
14. How many DHCP servers are sufficient for serving a network divided by two routers?
One DHCP server is enough if DHCP agents are in use.
15. For reliability, there are two DHCP servers in the network. How should the administrator assign the pool of available addresses for each of them: allocate nonoverlapping parts of the pool to each one, or assign the common pool for both?
16. Why an inverse DNS problem, namely, finding host names by known IP addresses, is not solved using the same approach as the one used for solving the direct problem (i.e., using the same zone and domain files organized as a tree corresponding to the name hierarchy)?
1. Suppose that some ISP has a Class B network address at its disposal. For addressing hosts of its own network, this ISP uses 254 addresses. Determine the maximum number of customers that can be served by this ISP if the sizes of their networks correspond to Class C. What mask should be set on the ISP's router connecting its network to the networks of its clients?
A byte is enough to specify 254 addresses. A class B network uses 2 bytes for hosts’ addresses. Thus, one of those bytes, namely the upper byte, can be used for subnet addressing, which gives 256 possible subnet addresses. As one address from this range will be used for a provider router interface then other addresses can be used for 255 clients’ network with maximum 254 nodes each. A provider router interface leading to a client network should use 255.255.255.0 mask.
2. What is the maximum theoretical number of subnets that you can organize if you have a Class C network at your disposal? What is the role of a network mask in this case? What is its value?