3Com 3 manual How Automatic IP Configuration Works

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How Automatic IP Configuration Works

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Automatic Process To detect its IP information using the automatic configuration process, the Switch goes through the following sequence of steps:

1The DHCP client that resides in the Switch makes up to four attempts to contact a DHCP server on the network requesting IP information from the server. The attempts are at 0, 4, 12, 28 second intervals.

■If a DHCP server is on the network and working correctly it responds to the clients request with an IP address (allocated from a pool of available addresses) and other parameters such as a subnet mask, default gateway, lease time, and any other options configured in the DHCP server.

The way a DCHP server responds is dependant on the DHCP server settings. Therefore the way your DHCP server responds may be different to the process outlined.

■If the DHCP process fails after 30 seconds on all four attempts, then the Switch activates its Auto-IP configuration feature.

2The Auto-IP feature starts with an IP address of 169.254.100.100. It uses the Address Resolution Protocol (ARP) to check to make sure this address is not already in use on the network. If not, it will allocate this default address to the Switch.

If this IP address is already in use, Auto-IP will check once every second for three seconds for an IP address on the 169.254.x.y subnet (where x = 1-254 and y = 0-255) (Auto-IP only uses addresses in the range 169.254.1.0 through to 169.254.254.255 as valid addresses.) Once Auto-IP has ensured that an IP address is not already in use on the network, it assigns it to the Switch with a subnet mask of 255.255.0.0 and a default gateway of 0.0.0.0.

3While the Auto-IP assigned address is in use:

■The Auto-IP client continues to check every 30 seconds (using ARP) to ensure that any other Auto-IP hosts have not mistakenly configured themselves using the same Auto-IP address.

■DHCP and BOOTP requests also continue in the background. The requests begin 3 minutes after either the Auto-IP address is assigned, or 125 attempts to establish a valid Auto-IP address, whichever occurs first. The requests proceed with DHCP requests for 1 minute; a 3 minute pause; DHCP requests for another minute; a 3 minute pause; BOOTP requests for one minute; a 3 minute pause; then the process repeats until a DHCP or BOOTP server answers the requests.

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Contents SuperStack 3Com Corporation 5400 Bayfront Plaza Santa Clara, California Contents Using Multicast Filtering Status Monitoring and Statistics IP Addressing About this Guide List conventions that are used throughout this guide ConventionsPddtechpubscomments@3com.com RelatedDocumentation CommentsRegistration ProductSwitch Features Page Software? What isSwitch Features ManagementSwitch Features Overview Flow Control Ports operating at 1000 Mbps only support full duplex modeFor more information about multicast filtering, see Using DuplexResilience Features For more information about STP and RSTP, see UsingEvent Notification Quality of ServiceFor more information about Quality of Service, see Using For more information about VLANs, see Setting Up Virtual Port Features Ports operating at 1000 Mbps support full duplex mode only Port Features Switch units connected using an aggregated link Aggregated Links Traffic Distribution and Link Failure on Aggregated Links 2 Gbps aggregated link between two Switch units Optimizing Bandwidth Relevant multicast group Using Multicast FilteringUsing Multicast Filtering Query Mode Query modeSnooping Mode Enabling Igmp Multicast Learning Igmp v2 protocolThat support IP Igmp multicast filtering works as followsIgmp Multicast Filtering Using Multicast Filtering Network Spanning TreeProtocol STP Ieee 802.1w standard What is STP? Traffic flowing through Bridge B Port Speed Link Type Path Cost 802.1D-1998 802.1w Using Resilience Features Port costs in a network Configuration 3 Redundancy for Cabling Error Configuration 1 Redundancy for Backbone LinkConfiguration 2 Redundancy through Meshed Backbone STP configurations Multiple VLANs Default BehaviorUsing STP on a Network withConfiguration that separates VLANs Using Resilience Features Database Entries What is the SwitchHow Switch Database?Databases entries can have three states Switch Database Entry StatesConverged network applications Used by organizations with a What is TrafficPrioritization? Available802.1D Priority Levels How Traffic Prioritization Works Traffic Prioritization Your SwitchConfiguring traffic prioritization for QoS on a Switch How traffic is processed to provide Quality of ServiceUsing Traffic Prioritization That allows you to monitor the traffic of LANs or VLANs What is RMON?Network efficiency and reduce the load on your network It improves your efficiency AlarmsEvents Rmon SwitchLow Threshold Statistic High Threshold Recovery Period Low Threshold Statistic High Threshold Recovery Status Monitoring and Statistics Hardware Status Monitoring Example device summary web Setting UP Virtual Lans VLANs provide extra security VLANs ease the movement of devices on networksVLANs help to control traffic Creating an Ieee 802.1Q Tagged Link MembershipTwo Vlans connected via a router Examples ConfigurationUsing Untagged Configure the VLANsAdd ports to the VLANs Configure the VLANs on SwitchAdd endstation ports on Switch 1 to the VLANs Check the Vlan membership for both switches Add port 12 on Switch 1 to the VLANsAdd endstation ports on Switch 2 to the VLANs Add port 11 on Switch 2 to the VLANsConfiguration How Automatic IP How Your SwitchObtains IP InformationHow Automatic IP Configuration Works Considerations Automatic IP configuration featureThat a Switch may change its IP address whilst in use Index Configuration RulesIP Addressing GlossaryPage Configuration Rules for Gigabit Ethernet Configuration RulesFast Ethernet configuration rules Configuration Rules for Fast Ethernet Appendix a Configuration Rules This chapter contains the following sections NetworkExample Segments are connected to the Switch which is positionedSimple Network Family and 4900 family can be used in your networkDual Speed Hub Switch Network Advanced NetworkImproving Resilience of YourTherefore the overall network performance EnhancingPerformance Simple Overview IP AddressesIP Address Obtaining a Registered IP AddressNetwork Portion Dotted Decimal NotationDecimal value of an octet whose bits are all 1s is Subnet mask Extending the Network Prefix Subnet Mask NumberingOr leave the field blank Glossary Glossary Fast Ethernet EndstationEthernet Ethernet addressIeee 802.1D GatewayHalf duplex HubLine speed See baud Glossary Rstp See Rapid Spanning Tree Protocol STP See Spanning Tree Protocol STP Page Glossary Numbers IndexIgmp multicast filtering 30 Internet Addresses 85 InterNIC Sub-networks. See subnets Switch Database

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