Cisco WS-X6K-S2-PFC2 Software Guide - Page 257

Chapter 14 Configuring MLS Understanding How Layer 3 Switching Works Figure 14-1 IP MLS Example Topology Source IP Address 171.59.1.2 Destination IP Address 171.59.3.1 171.59.1.2 171.59.2.2 171.59.2.2 171.59.1.2 Application FTP Rewrite Src/Dst MAC Address Dd:Bb Destination VLAN Marketing HTTP Dd:Cc Engineering HTTP Dd:Aa Sales MAC = Aa Subnet 1/Sales Host A 171.59.1.2 MAC = Bb MAC = Dd MSFC Subnet 3/Marketing Host B 171.59.3.1 Subnet 2/Engineering MAC = Cc Data 171.59.1.2: 2000 Aa:Dd Host C 171.59.2.2 Data 171.59.1.2: 2000 Dd:Cc 25481 Figure 14-2 shows a simple IPX MLS network topology. In this example, Host A is on the Sales VLAN (IPX address 01.Aa), Host B is on the Marketing VLAN (IPX address 03.Bb), and Host C is on the Engineering VLAN (IPX address 02.Cc). When Host A initiates a file transfer to Host B, an IPX MLS entry for this flow is created (this entry is the first item in the table shown in Figure 14-1). The PFC stores the MAC addresses of the MSFC and Host B in the IPX MLS entry when the MSFC forwards the first packet from Host A through the switch to Host B. The PFC uses this information to rewrite subsequent packets from Host A to Host B. Similarly, a separate IPX MLS entry is created in the MLS cache for the traffic from Host A to Host C, and for the traffic from Host C to Host A. The destination VLAN is stored as part of each IPX MLS entry so that the correct VLAN identifier is used when encapsulating traffic on trunk links. 78-13315-02 Catalyst 6000 Family Software Configuration Guide-Releases 6.3 and 6.4 14-9