You can attach a monitoring device to the mirrored port, such as a sniffer or an RMON probe, to view details about the packets that pass through the first port. This is useful for network monitoring and troubleshooting purposes.
Simple Network Management Protocol (SNMP)
The Simple Network Management Protocol (SNMP) is an open system interconnection (OSI) layer 7 (application layer) protocol for remotely monitoring and configuring network devices. SNMP enables network management stations to read and modify the settings of gateways, routers, switches and other network devices. SNMP can be used to perform many of the same functions as a directly connected console, or can be used within an integrated network management software package such as IBM® NetView or Hewlett Packard OpenView. SNMP performs the following functions:
•Sending and receiving SNMP packets using the IP protocol
•Collecting information about the status and current configuration of network devices
•Modifying the configuration of network devices
The switch module has a software program, called an agent, that processes SNMP requests, but the user program that makes the requests and collects the responses runs on a management station (a designated computer on the network). The SNMP agent and the user program both employ the user datagram protocol/Internet protocol (UDP/IP) to exchange packets.
Authentication
The authentication protocol ensures that both the SNMP agent in the switch module and the remote user SNMP application program discard packets from unauthorized users. Authentication is accomplished by using community strings which function like passwords. The remote user SNMP application and the switch module’s SNMP agent must use the same community string. SNMP community strings of up to 20 characters can be entered using the CLI snmp community commands described in Chapter 7 “Command Line Interface Management” on page 155.
Switching concepts
This section introduces the concepts and protocols relevant to the switching functionality of the Intel® Blade Server Ethernet Switch Module IXM5414E.
Packet forwarding
The switch module uses a forwarding table to store the information that it collects about the location of devices on the network. The table holds destination MAC addresses and the destination port number through which they can be reached. Packets sent to known addresses are therefore transmitted only through relevant destination ports, thus reducing network traffic. For example, if port 1 receives a packet destined for a station on port 2, the switch module transmits that packet through port 2 only and transmits nothing through the other ports. Creating the table is referred to as learning the network topology.
An aging timer is used to make sure that the table is updated if devices are moved. Dynamic entries, those learned by the switch by observing network traffic, are deleted from the table if they are not accessed within the aging time. Static entries, those entered by a network administrator, are not subject to the aging process.
24 | Intel® Blade Server Ethernet Switch Module IXM5414E |
