Address Aliasing
Address aliasing is defined as mapping 32 multicast IP addresses to a single Layer 2 MAC address. A multicast Layer 3 address could map to a system MAC address that is used by the switch, which is a potential risk. Any packets destined to the system CAM entries are directly sent to the NMP because it is assumed that the packets are part of the control traffic rather than user traffic. As a result, network outages can occur if multicast user traffic is mapped to a system CAM entry.
Look at an example to solidify the problem with address aliasing. Both Host1 and Host2 are in VLAN 3 as shown in Figure 9-9. Two types of supervisors are used in this design. Their handling of address aliasing will become apparent shortly.
Figure 9-9. Address Aliasing
Example 9-8 shows two outputs from Switch1 and Switch2, respectively.