In a network with dozens of switches, how many root bridges would you have?

No DR is assigned on any type of point-to-point link. No DR/BDR is assigned on the NBMA point-to-multipoint due to the hub/spoke topology. DR and BDR are elected on broadcast and non-broadcast multi-access networks. Frame Relay is a non-Broadcast Multi-Access (NBMA) network by default.

To see console messages through your Telnet session, you must enter the terminal monitor command.

A /28 is a 255.255.255.240 mask. Let's count to the ninth subnet (we need to find the broadcast address of the eighth subnet, so we need to count to the ninth subnet). Starting at 16 (remember, the question stated that we will not use subnet zero, so we start at 16, not 0), 16, 32, 48, 64, 80, 96, 112, 128, 144. The eighth subnet is 128 and the next subnet is 144, so our broadcast address of the 128 subnet is 143. This makes the host range 129-142. 142 is the last valid host.

Standard and extended access control lists (ACLs) are used to configure security on a router.

The default configuration setting is 0x2102, which tells the router to load the IOS from flash and the configuration from NVRAM. 0x2142 tells the router to bypass the configuration in NVRAM so that you can perform password recovery.

The default configuration setting of 0x2102 tells the router to look in NVRAM for the boot sequence.

Flow control allows the receiving device to control the transmitter so the receiving device's buffer does not overflow.

The tracert command is a Windows command and will not work on a router! A router uses the traceroute command.

If you are on a 2950 switch, then the interface command is just switchport mode trunk, since the 2950 can only run the IEEE 802.1Q version. However, a 3550 can run both ISL and 802.1Q, so you must use the encapsulation command. The argument to choose 802.1Q for a trunking protocol is dot1q.

To test the local stack on your host, ping the loopback interface of 127.0.0.1.