438 G8264 Application Guide for ENOS 8.4ECMP Static RoutesEqual‐Cost Multi‐Path (ECMP) is a forwarding mechanism that routes packetsalong multiple paths of equal cost. ECMP provides equally‐distributed link loadsharing across the paths. The hashing algorithm used is based on the destination IPand source IP (DIPSIP) addresses or only on the source IP address (SIP). ECMProutes allow the switch to choose between several next hops toward a givendestination. The switch performs periodic health checks (ping) on each ECMPgateway. If a gateway fails, it is removed from the routing table, and an SNMP trapis sent.OSPF IntegrationWhen a dynamic route is added through Open Shortest Path First (OSPF), theswitch checks the route’s gateway against the ECMP static routes. If the gatewaymatches one of the single or ECMP static route destinations, then the OSPF route isadded to the list of ECMP static routes. Traffic is load‐balanced across all of theavailable gateways. When the OSPF dynamic route times out, it is deleted from thelist of ECMP static routes.ECMP Route HashingYou can configure the parameters used to perform ECMP route hashing, asfollows: sip: Source IP address dipsip: Source IP address and destination IP address (default)Note: The sip and dipsip options enabled under ECMP route hashing or in portLAG hashing (portchannel thash) apply to both ECMP and LAG features (theenabled settings are cumulative). If unexpected ECMP route hashing occurs,disable the unwanted source or destination IP address option set in LAG hashing.Likewise, if unexpected LAG hashing occurs, disable any unwanted options set inECMP route hashing.The ECMP hash setting applies to all ECMP routes.
