Operation Manual – IPv4 RoutingH3C S5500-EI Series Ethernet Switches Chapter 4 IS-IS Configuration4-34To do… Use the command… RemarksEnable the interface tosend small hello packetsthat have no padding fieldisis small-helloRequiredStandard hello packetsare sent by default.4.5.12 Enabling SNMP TrapFollow these steps to enable IS-IS trap:To do… Use the command… RemarksEnter system view system-view ––Enter IS-IS view isis [ process-id ] ––Enable SNMP Trap is-snmp-traps enable RequiredEnabled by default4.6 Configuring IS-IS GRAn ISIS restart may cause the termination of the adjacencies between a restartingrouter and its neighbors, resulting in a transient network disconnection.IS-IS Graceful Restart can help to solve this problem by notifying its neighbors itsrestarting state to allow them to reestablish the adjacency without removing it. TheIS-IS Graceful Restart provides the following features:z When restarting ISIS, a Graceful Restart capable device will resend connectionrequests to its neighbors instead of terminating their neighboring relationships.z Graceful Restart minimizes network disruption caused by LSDB synchronizationbefore LSP packets generation.z When a router starts for the first time, it sets the overload bit in LSP packets beforeLSDB synchronization is complete, which ensures no routing loop is created.The Graceful Restart interval on a router is used as the holdtime in the IS-IS HelloPDUs so that its neighbors can maintain the adjacencies within the interval after therouter restarts.By setting the SA (Suppress-Advertisement) bit in the hello PDUs sent by the GRRestarter, its neighbors will not advertise adjacencies within the specified period untilthe completion of LSDB synchronization between the GR Restarter and its neighbors.This feature helps to effectively avoid blackhole routes due to the sending or receivingof LSPs across the restart.
