OSPF Commands 1099• Learned Dynamically: Routing protocols can learn ECMP routes. Forexample, if OSPF is configured on both links connecting Router A toRouter B with interface addresses 10.1.1.2 and 10.1.2.2 respectively, andRouter B advertises its connection to 20.0.0.0/ 8, then Router A computesan OSPF route to 20.0.0.0/8 with next hops of 10.1.1.2 and 10.1.2.2.PowerConnect routing stores static and dynamic routes in a single combinedrouting table. RTO accepts ECMP routes, but it is important to understandthat RTO does not combine routes from different sources to create ECMProutes. Referring to the above configuration, assume OSPF is only configuredon the 10.1.1.2 Router B interface connecting Router A and Router B. Thenon Router A, OSPF reports to RTO a route to 20.0.0.0/8 with a next hop of10.1.1.2. If the user configures a static route to 20.0.0.0/8 with a single nexthop of 10.1.2.2, RTO does NOT combine the OSPF and static route into asingle route to 20.0.0.0/8 with two next hops. All next hops within an ECMProute must be provided by the same source.On StrataXGS® IV platforms, the ECMP hashing support is extended toEnhanced hashing mode, which provides improved load-balancingperformance. ECMP hashing on these platforms has the following features:• MODULO-N operation based on the number N of next hops in the route.• Packet attributes selection based on the packet type. For IP packets, thefollowing fields are used: Source IP address, Destination IP address,TCP/UDP port, IPv4 Protocol, IPv6 next header.Forwarding of OSPF Opaque LSAs Enabled byDefaultPowerConnect supports the flooding capability of opaque LSAs.PowerConnect cannot originate or process opaque LSAs. In the past, thecapability to flood opaque LSAs was disabled by default.Passive InterfacesThe passive interface feature is used to disable sending OSPF routing updateson an interface. An OSPF adjacency will not be formed on such an interface.On a passive interface, subnet prefixes for IP addresses configured on theinterface will continue to be advertised as stub networks.
