Configuring Core1 for SAN

  1. After connecting SAN switches to Core1, spanning-tree caused the Internet uplinks of those switches to be blocked. In order to solve this problem we disabled the spanning-tree on corresponding ports in Core1 and the SAN switches. The other option was using Multiple Spanning-Tree protocol (MST) which is more involved and creates unnecessary complexity.
  2. The other issue was the jumbo frames on Core1 switch. Since layer 3 devices negotiate and agree on the MTU (for example iSCSI server and client) the layer 2 devices in the path must have a larger or equal MTU than the one that is agreed upon in layer 3. Otherwise there will cause the iSCSI connection to flip flop and load increases in the servers. This is because there is no negotiation for MTU between layer 3 and layer2 and it is the responsibility of network administrator to make sure that layer 2 MTU in all devices in the path is equal or greater than the MTU in layer 3.