Chapter 7's Review Questions
| 1: | Compare ISL to 802.1Q. |
| A1: | Answer: When a frame goes out an
ISL
trunk, it gets encapsulated by tagging it with a 26-byte
ISL
header and another 4-byte
CRC
trailer. Therefore, it is possible for an Ethernet frame to be 1518 + 30 = 1548 bytes.
ISL
trunks can carry not only Ethernet traffic, but also Token Ring and FDDI, due to the
reserved field
in the
ISL
header.
Unlike the Cisco proprietary ISL, IEEE 802.1Q offers multivendor VLAN multiplexing support. As shown in Figure 7-5, ISL is more of an encapsulation (external tagging), whereas 802.1Q is an internal frame tagging method of VLAN identification. |
| 2: | Can you change the management VLAN? |
| A2: | Answer: Yes, you can change the management VLAN. However, some switches require it to be VLAN1. For example, on a CatOS box, use the set int sc0 vlan# ipaddress subnetmask command. |
| 3: | Why should you use a separate management VLAN? |
| A3: | Answer: Always use a separate management VLAN to isolate user problems. If a broadcast storm occurs, it could spread throughout the entire VLAN. On the management VLAN, this would eventually cause drastic CPU overload. Protocol traffic such as CDP, VTP, and PAgP use VLAN1. You do not want your other management traffic such as telnet, SNMP, VMPS, Syslog to interfere if you can help it. The management traffic uses whatever VLAN that is assigned to the sc0 port. STP is sent on each VLAN. If the Supervisor CPU is saturated by processing broadcasts in the management VLAN, it may not be able to keep up with STP BPDUs. |
| 4: | What does a transparent mode–configured Catalyst do with a VTP update message? |
| A4: | Answer: A transparent mode-configured Catalyst ignores VTP update messages unless it has trunk ports configured so that it can act as an intermediary and flood the frame to other switches. |
| 5: | You incorrectly associated port 8 with VLAN8, so you issue the following command: clear vlan 8 to clear the port from VLAN8 and back to the default VLAN1. However, the port status is still showing as inactive. How can you fix this issue? |
| A5: | Answer: You need to associate port 8 with VLAN1. Although all ports originally start in VLAN1, when you change them to another VLAN they do not automatically go back to VLAN1. Instead they are sitting in an inactive state. |
| 6: | The lab technician was nice enough to give you his switch to replace a production switch that you were having problems with. He quickly clears all the VLANs on the switch and hands it over to you. When you plug the switch into your network, you quickly realize that all your other VLANs disappear. Where did you go wrong? Is there anything you can do to avoid such issues? |
| A6: | Answer: Evidently, the lab switch had the highest revision number; therefore, you just learned how to play “vlan wipeout” and have lots of unhappy users. Sounds like lots of work, but perhaps beforehand you should have made sure your switches were either using all VTP transparent mode or a couple of VTP servers with mostly VTP clients. If you would have just reset the VTP domain name on the lab switch, you would have been fine. |
| 7: | You want to verify that you configured portfast on the 3512XL port fa0/2. How can you accomplish this? |
| A7: | Answer: sh spanning-tree int fa0/2. Alternatively, you could look at the configuration file. Likewise on the 2900 CatOS switch, you could check the portfast status of hostc using sh port spantree 1/2. |
| 8: | Routing provides __________ connectivity, whereas trunking provides __________ connectivity. |
| A8: | Answer: Routing provides inter-VLAN connectivity, whereas trunking provides intra-VLAN connectivity. |
| 9: | There are three major steps for working VLANs. What are they? |
| A9: | Answer: 1. Create and define a VTP domain. 2. Create the VLAN. 3. Associate a port(s) with the VLAN. |
| 10: | Can VLANs assist with people trying to Sniff the network? |
| A10: | Answer: Yes, VLANs can assist with people trying to Sniff the network. Remember VLANs are subnets. The VLAN ports are switch ports, which in fact have a certain level of security on their own. You must configure port monitoring before you can run a protocol analyzer. |
| 11: | In a router-on-a-stick configuration, as in the chapter scenario, what would you expect to be the first hop if hosta were to tracert to hostc? |
| A11: | Answer: In a router-on-a-stick configuration, all inter-VLAN traffic goes through the stick. Therefore, in the chapter scenario that is 192.168.5.30 for VLAN1. |
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