| 1: | Identify one criterion to help determine a subnet mask for classless addressing when designing a network-addressing scheme. |
| A1: | Questions to ask include the following: -
- How many networks are there in the network? -
- How many hosts are there on the largest subnet? |
| 2: | With a classless address of 204.1.64.0/20, what is the range of classful addresses that are included in the address? Write your answer in dotted decimal and the third octet in binary notation. |
| A2: | The address 204.1.64.0 /20 includes the Class C addresses 204.1.64.0 to 204.1.79.0; this is illustrated in both dotted decimal and binary notation in the following table. | Binary Notation | Decimal Notation | | 01000000 | 204.1.64.0 | | 01000001 | 204.1.65.0 | | 01000010 | 204.1.66.0 | | 01000011 | 204.1.67.0 | | 01000100 | 204.1.68.0 | | 01000101 | 204.1.69.0 | | 01000110 | 204.1.70.0 | | 01000111 | 204.1.71.0 | | 01001000 | 204.1.72.0 | | 01001001 | 204.1.73.0 | | 01001010 | 204.1.74.0 | | 01001011 | 204.1.75.0 | | 01001100 | 204.1.76.0 | | 01001101 | 204.1.77.0 | | 01001110 | 204.1.78.0 | | 01001111 | 204.1.79.0 | |
| 3: | What is a discontiguous network? |
| A3: | A discontiguous network is a network in which a classful network is separated by another classful network. Therefore, the original classful network is no longer contiguous because an intervening Internet number has segmented or divided it. |
| 4: | For VLSM to be available as a design option in the network, what characteristic must the routing protocol possess? |
| A4: | The routing protocol must send the prefix or subnet mask as part of the routing update. |
| 5: | If summarization is to be implemented in the network, name one design criterion for the addressing scheme that must be in place. |
| A5: | For VLSM to work, the addressing scheme must be hierarchical, allowing the upstream devices to share the same high-order bits as the downstream devices. |
| 6: | If the host portion of a subnet has been used to identify end devices, can that subnet be used again for VLSM? |
| A6: | It is not possible to use a subnet for addressing hosts or to further subnet the network using VLSM. The addresses would be seen as duplicate addresses. |
| 7: | Give one example of when route summarization would not be a good solution. |
| A7: | Route summarization is not useful in the following circumstances: -
- There are discontiguous networks in the organization. -
- A specific subnet needs to be seen throughout the network. -
- The addressing scheme does not support summarization. No common high-order bits are shared in the network-addressing scheme. -
- Access lists require detailed information, which summarization suppresses. |
| 8: | Give one reason for implementing route summarization. |
| A8: | Route summarization is useful for the following reasons: -
- To keep the routing tables small -
- To keep the network overhead low -
- To hide the network details from the rest of the organization -
- To prevent flapping links from affecting the rest of the network |
| 9: | Given an address of 133.44.0.0 and a prefix mask of /25, how many networks can be addressed, and how many hosts can exist on each network? Write the first and last possible subnets in binary and decimal notation. |
| A9: | For the network address of 133.44.0.0, the subnet mask of 255.255.255.128 would enable you to address 510 subnets with 126 hosts on each subnet. This complies with the subnetting rule of not allocating addresses with all 0s or all 1s. The following table illustrates the first and last subnet in their binary and decimal notation formats. | Binary Notation | Decimal Notation | | 00000000.10000000 | 133.44.0.128 | | 11111111.00000000 | 133.44.255.0 | |
| 10: | What class of address is 131.188.0.0, and how many hosts can be addressed if no subnetting is used? |
| A10: | 131.188.0.0 is a Class B address and can address more than 65,000 hosts on one network if no subnetting is used. |
| 11: | Write out the decimal notation of the following subnet mask presented in the binary notation of 11111111.11111111.11111111.11111000. |
| A11: | The decimal notation of the subnet mask would be 255.255.255.248. |
| 12: | Is 201.111.16.0/20 a valid subnet mask? |
| A12: | Yes, this is a valid mask, and it will provide 16 consecutive Class C addresses to the organization. |
| 13: | Briefly define route summarization. |
| A13: | Route summarization is the method of including many subnets in a few routing entries. |
| 14: | What sort of design scheme does route summarization require? |
| A14: | Route summarization requires a hierarchical addressing scheme. |
| 15: | In route summarization, in which direction is the network/host boundary in the subnet mask moved? |
| A15: | In route summarization, the subnet mask is shifted to the left. |
| 16: | Explain how summarization allows for smaller routing tables? |
| A16: | Summarizing is the consolidation of multiple routes into a single advertisement. |
| 17: | What is the subnet mask for a /21 prefix? |
| A17: | The subnet mask is 255.255.248.0. |
| 18: | What is the default subnet mask for the IP address 192.18.16.15? |
| A18: | The subnet mask is 255.255.255.0. |
| 19: | State whether 131.104.0.0/13 is an example of CIDR or VLSM routing. |
| A19: | The address 131.104.0.0/13 is an example of CIDR routing because it is summarizing Class B addresses within the Internet routing tables. |
| 20: | State how many classful addresses are summarized in the address 131.104.0.0/13. |
| A20: | Eight Class B addresses are summarized in the address 131.104.0.0 /13. The range of addresses is 131.104.0.0131.111.0.0/16. |
