2-5Configuring a Classical IP ATM Network2.2.2 Operating with ILMI SupportCabletron Systems switches running software version 3.0 or greater providesupport for ILMI. If ILMI is supported on all of the switches and hosts in agiven network, when a switch control processor (SCP) boots up, ILMI enablesthe SCP to discover all of the hosts attached to it and to send its NSAP prefixassociated with the port to those hosts dynamically. In return, the hostprepends that prefix to its ESI and selector fields, forming a complete NSAPaddress. The host then notifies the SCP of its complete NSAP address. Theseregistration SNMP messages are sent and received over AAL5 using VPI: 0,VCI: 16. Once ILMI registration has been completed, then connection setupcan occur.If a host changes network ports after an NSAP address has been registered forits interface, all existing connections will be closed. If the new port is on a dif-ferent SCP, a new NSAP address (with a different network address prefix)will be registered. The host can then begin to establish new connections.2.2.3 Operating without ILMI SupportIf ILMI is not supported on a particular SCP or host in a given network, thenthe NSAP addresses must be manually configured. Because a non-Cabletronswitch does not support ILMI, it can not supply an NSAP prefix to the hosts.Therefore, the user must assign a unique, valid prefix to the switch. Addition-ally, the same prefix should be used for all hosts in the LIS.On the host, atmarp -n (8c) is used to configure the NSAP address for a spe-cific interface. The SCP directly attached to this interface is then informed ofthis NSAP address/port combination through commands in the ATM Man-agement Interface (AMI). Once the host and network have both beeninformed of this NSAP address/port pair, the host may begin signalling.Once an interface’s NSAP address has been set, it is possible to change it byfirst running atmarp -n to set the new address, and then bringing the inter-face down and back up (ifconfig qaXX down; ifconfig qaXX up) for theaddress change to take effect.2.2.4 ConfigurationThe choice to use ILMI for address registration is made at software installa-tion time. Since ILMI uses SNMP as its management protocol, the use of ILMIis tied into snmpd. The choice can be made to run FORE’s SNMP agent anduse ILMI (snmpd), run FORE’s SNMP agent without using ILMI (snmpd -n),or just use ILMI (snmpd -i or ilmid -i). The commands to run the chosen dae-mon, or to configure a host’s NSAP address statically when not running ILMI,are placed in the firmware download script.
