| 1. | By default, how long are CAM table entries kept before they are aged out? |
| Answer: | 300 seconds |
| 2. | A TCAM lookup involves which values? |
| Answer: | Mask, Value, Result |
| 3. | How many table lookups are required to find a MAC address in the CAM table? |
| Answer: | 1 |
| 4. | How many table lookups are required to match a packet against an access list that has been compiled into 10 TCAM entries? |
| Answer: | 1 |
| 5. | How many value patterns can a TCAM store for each mask? |
| Answer: | 8 |
| 6. | Can all packets be switched in hardware by a multilayer switch? |
| Answer: | No; some must be flagged for process switching by the switch CPU. |
| 7. | Multilayer switches must rewrite which portions of an Ethernet frame? |
| Answer: | Source and destination MAC addresses IP Time-To-Live Checksums |
| 8. | If a station receives only Ethernet frames and doesn't transmit anything, how will a switch learn of its location? |
| Answer: | You must configure a static CAM entry with the station's MAC address and the switch port where it is located. Otherwise, the switch must flood every frame destined for that host out every switch port in an effort to find it. |
| 9. | What is a TCAM's main purpose? |
| Answer: | To process access lists as a single table lookup |
| 10. | Why do the TCAM mask and pattern fields consist of so many bits? |
| Answer: | So that a combination of several address fields in a frame can be inspected at once |
| 11. | In a multilayer switch with a TCAM, a longer access list (more ACEs or statements) takes longer to process for each frame. True or false? |
| Answer: | False |
| 12. | A multilayer switch receives a packet with a certain destination IP address. Suppose that the switch has that IP address in its Layer 3 forwarding table but has no corresponding Layer 2 address. What happens to the packet next? |
| Answer: | The switch CPU sends an ARP request. |
| 13. | Suppose that a multilayer switch can't support a protocol with CEF, and it relies on fallback bridging. Can the switch still route that traffic? |
| Answer: | No. That traffic is transparently bridged. An external multilayer switch or router is required to route the bridged packets. |
| 14. | To configure a static CAM table entry, the mac address-table static mac-address command is used. Which two other parameters also must be given? |
| Answer: | vlan vlan-id interface type mod/num |
| 15. | As a network administrator, what aspects of a switch TCAM should you be concerned with? |
| Answer: | The size of the TCAM resources |
| 16. | What portion of the TCAM is used to evaluate port number comparisons in an access list? |
| Answer: | LOU |
| 17. | Someone has asked you where the host with MAC address 00-10-20-30-40-50 is located. Assuming that you already know the switch it is connected to, what command can you use to find it? |
| Answer: | show mac address-table dynamic address 0010.2030.4050 |
| 18. | Complete this command to display the size of the CAM table: show mac ____________. |
| Answer: | address-table count |
| 19. | What protocol is used to advertise CAM table entries among neighboring switches? |
| Answer: | None; the entries are not advertised. |
| 20. | Suppose that a host uses one MAC address to send frames and another to receive them. In other words, one address will always be the source address sent in frames, and the other is used only as a destination address in incoming frames. Is it possible for that host to communicate with others through a Layer 2 switch? If so, how? |
| Answer: | Yes, but not very efficiently. The Layer 2 switch will learn one of the host's MAC addresses as the host sends frames. That address will be seen as the source address on frames arriving at the switch. However, because the second MAC address never is used to send frames, the switch will never be capable of learning of its existence. When frames are sent to the host using that second MAC address, the switch is forced to flood the frames out all relevant switch ports. The host receives those frames only because it is connected to a port where the frames were flooded. All other hosts on the same VLAN also receive the flooded frames, even though they have no interest in that traffic. |
