MAC Tables

Question 1

How does a switch build its MAC address table?

Answer 1

A switch builds its MAC address table by learning the source MAC addresses of incoming frames and associating them with the ports on which the frames are received.

Question 2

What is a MAC address table in a switch?

Answer 2

A MAC address table, also known as a forwarding table, is used by switches to map MAC addresses to specific ports, enabling efficient frame forwarding.

Question 3

What happens if a MAC address is not found in the MAC address table?

Answer 3

If a MAC address is not found in the table, the switch will broadcast the frame to all ports, except the port it was received on, to locate the destination device.

Question 4

How long does a MAC address remain in the MAC address table?

Answer 4

A MAC address typically remains in the MAC address table for a default aging time of 300 seconds (5 minutes) unless traffic is received from the address, in which case the timer is reset.

Question 5

How can you view the MAC address table in Junos OS?

Answer 5

You can view the MAC address table in Junos OS using the command: show ethernet-switching table.

Question 6

What is a MAC address collision?

Answer 6

A MAC address collision occurs when two devices on the network claim the same MAC address, which can cause frame forwarding issues.

Question 7

How does a switch handle a MAC address table overflow?

Answer 7

If the MAC address table is full, the switch will start flooding frames to all ports, similar to the behavior of an unknown MAC address, until the table space is available again.

Question 8

What is the purpose of the “static” MAC address entry in a switch’s MAC address table?

Answer 8

A static MAC address entry is manually configured and ensures that the switch always forwards frames to the specified port, regardless of learning dynamic entries.

Question 9

How can you delete a specific MAC address from the MAC address table?

Answer 9

You can delete a specific MAC address from the table in Junos OS using the command: clear ethernet-switching table mac-address <mac-address>.</mac-address>

Question 10

What does the MAC address table look like in terms of its entries?

Answer 10

The MAC address table contains entries with the MAC address, associated VLAN ID, port number, and the age of the entry.