3Com Router 3000 Ethernet FamilyConfiguration Guide Chapter 5 Integrated IS-IS Configuration3Com Corporation5-165.2.15 Configuring Route AggregationRoute aggregation aggregates multiple routes in the same segment but differentsubnets into a single route. The segment does not necessarily mean a natural segment,but it can also be a subnet segment or supernet segment. All the subnet routes to beaggregated must have the same next hop.Route aggregation can effectively minimize route information and routing tables.Perform the following configuration in IS-IS view.Table 5-19 Configure route aggregationOperation CommandSet route aggregation summary ip-address ip-mask [ level-1 |level-1-2 | level-2 ]Delete the route aggregation undo summary ip-address ip-mask[ level-1 | level-1-2 | level-2 ]By default, the system disables route aggregation.5.2.16 Configuring Overload Flag BitSometimes, the router in the IS-IS domain may encounter some problems in operationthus error may occur in the whole routing area. In order to avoid this problem, we canset the overload flag bit for this router.When the overload threshold is set, other routers should not send this router thepackets which should be forwarded by this router.Perform the following configuration in IS-IS view.Table 5-20 Configure overload flag bitOperation CommandSet overload flag bit set-overloadRemove the overload flag bit undo set-overloadBy default, no over load bit is set.5.2.17 Configuring to Ignore the LSP Checksum ErrorsWhen the local IS-IS receives an LSP packet, it will perform checksum check to it. Bydefault, if the checksum in the packet is inconsistent with the calculated check sum, theLSP will be dropped. But if we set to ignore the checking error through the commandignore-lsp-checksum-error, this packet will be processed as a normal one even if theLSP checksum errors are found.
