BROCADE IP PRIMER

49FLinkPower50FConsole1 3 5 7 9 1113 15 17 19 21 2325 27 29 31 33 3537 39 41 43 45 471F 2F 3F 4F2 4 6 8 10 1214 16 18 20 22 2426 28 30 32 34 3638 40 42 44 46 48Chapter 7: Link Aggregation (Trunks)Static TrunksStatic trunks are trunks that are configured once, and then, essentially, leftalone. They don't change. For example, let's say you've configured a two-porttrunk from one switch to another. Later on, you decide that you actually needto make it a four-port trunk. To create this four port trunk, you must firstremove the two-port trunk, and then rebuild the trunk as a four-port trunk.There's no way to simply “expand” the existing trunk.Static trunks come in two varieties: switch and server.Switch TrunksSwitch trunks are designed for communication between two switches. All ofthe examples you've seen so far are switch trunks. These are designed to provideredundancy and greater throughput between switches.On JetCore switches, the trunk load balances traffic based on the destinationaddress. If the traffic is pure Layer 2 traffic, it is load balanced by the destinationMAC address of the traffic. If the traffic is Layer 3 (or higher) traffic, it willbe load balanced by the destination Layer 3 address (e.g., IP address, IPXaddress, etc.). The initial choice (for the first packet or frame) is decidedround-robin (e.g., first link 1, then link 2, then link 1, etc.). Once a destinationaddress has been tied to a particular link in the trunk, the switch will keep thisinformation in a table, and future traffic will travel down the same link.Newer switches provide the same load balancing options as server trunks.Server TrunksServer trunks are designed for communication between a single host (orserver) and a switch. For this, you'll need to have a server with multiple NICs.The server will also need to have a link aggregation driver (this driver will varydepending on the manufacturer of the NICs and the operating system of theserver). These are designed to provide link redundancy and increased throughputfor the server.With server trunks, the traffic is load balanced by source and destinationaddresses. If the traffic is pure Layer 2 traffic, it is load balanced by the sourceand destination MAC address of the frame. If the traffic is pure Layer 3 traffic,it is load balanced by the source and destination Layer 3 address (e.g., IPaddress, IPX address, etc.). If the traffic is TCP/IP, it is load balanced using thesource and destination IP address and the source and destination TCP/UDPport number. This adds a lot more granularity. Here, it is possible that a singlesource going to the same destination engaging more than one conversationwill likely use different trunk links. This maximizes the bandwidth of the trunk.160 Brocade IP Primer