Answers to Chapter Review Questions

     

A1:	We need to run 16 linkloop commands (each card needs to test the connection through the switch/bridge to each of the four cards on the other side of the connection). If none of the linkloop commands is the problem, any of the following could be the problem: The kernel does not have the necessary networking drivers loaded. Hardware problems with each card. The cables used may be wrong/unsupported/faulty. The switch/bridge may be filtering MAC addresses on a port-by-port basis. The switch/bridge may not support the 802.1 Spanning Tree algorithm.
A2:	Yes, the machines will be able to communicate. Although this configuration is possible, it is less than ideal. The concept here is the basic function of IP: to send packets to a local node ( consult the ARP cache) or to a distant network (consult the routing table). In this case, we will not see a conflict at the MAC level because the duplicate MAC addresses are on distant networks. When communicating using IP addresses, the IP software on node Fin100 will realize that it needs to communicate with network-25. To do so, it will send its packets to router1 (by consulting its routing table). In order to do so, Fin100 needs to know the MAC address of router1, not the MAC address of the machine it is eventually communicating with. router1 will then forward the packets through the corporate Intranet eventually arriving at router15, which will forward them to node Corp100. The reverse process will occur to send packets back to node Fin100.
A3:	I need 16 networks, therefore I need 5 bits (2 5 >= 16 + 2) of my host address as my subnet mask. Subnet mask = 255.255.255.248 I will be able to configure 2 3 “ 2 = 6 nodes per subnet (do not use all 0's or all 1's for node addresses because they are used for the network and broadcast addresses, respectively). Network addresses: Node1: 192.168.128.155 “ Network address = 192.168.128.152 Node2: 192.168.33.66 “ Network address = 192.168.128.64
A4:	The reason it may take some time before more devices on the Internet use IPv6 addresses is that a number of the devices/routers that make up the Internet use hardware EEPROM-chips/cache-memory chips that are hard-wired to manipulate 32-bit numbers, i.e., IPv4 addresses. In order for them to support IPv6 addresses, we would need to update the internal chips in question, replace the entire device for a device that supports the 128-bit IPv6 address, or if possible update the firmware of the device such that it can support a 128-bit address while operating with 32-bit numbers . MAC address = 0x080009bbbbbb - IPv6 link-local address = fe80::a00:09ff:febb:bbbb/10
A5:	The reason we cannot mix link technologies is that APA is operating at the link-level and technologies such as FDDI and 100-BaseT have very different packet formats and underlying media access definitions that mean the technologies are not interchangeable at the link-level. LAN Monitor operates in an Active Hot Standby mode whereby packets are sent down each link in the aggregate. Hot Standby operates in Active Standby mode where packets are sent down the primary link and moved to a standby link only in the event of a failure of the primary. LAN Monitor is, therefore, constantly testing the availability of all the links in the aggregate and will detect a failure in any link quicker than Hot Standby can.