782 BigIron RX Series Configuration Guide53-1001986-01Configuring route reflection parameters26• Set the maximum number of paths. The default maximum number of BGP4 load sharing pathsis 1, which means no BGP4 load sharing takes place by default. Refer to “Changing themaximum number of shared BGP4 paths” on page 759.NOTEThe maximum number of BGP4 load sharing paths cannot be greater than the maximumnumber of IP load sharing paths.How load sharing affects route selectionDuring evaluation of multiple paths to select the best path to a given destination for installment inthe IP route table, the last comparison the device performs is a comparison of the internal paths.• When IP load sharing is disabled, the device prefers the path to the router with the lower routerID if the compare-routerid command is enabled.• When IP load sharing and BGP4 load sharing are enabled, the device balances the trafficacross the multiple paths instead of choosing just one path based on router ID.Refer to “How BGP4 selects a path for a route” on page 732 for a description of the BGP4algorithm.When you enable IP load sharing, the device can load balance BGP4 or OSPF routes across up tofour equal paths by default. You can change the number of IP load sharing paths to a value from 2– 8.For more information on how load sharing works on the device, refer to “Configuring IP loadsharing” on page 207.Configuring route reflection parametersNormally, all the BGP routers within an AS are fully meshed. Each of the routers has an IBGPsession with each of the other BGP routers in the AS. Each IBGP router thus has a route for each ofits IBGP neighbors. For large ASs containing many IBGP routers, the IBGP route information in eachof the fully-meshed IBGP routers can introduce too much administrative overhead.To avoid this problem, you can hierarchically organize your IGP routers into clusters.• A cluster is a group of IGP routers organized into route reflectors and route reflector clients.You configure the cluster by assigning a cluster ID on the route reflector and identifying the IGPneighbors that are members of that cluster. All the configuration for route reflection takesplace on the route reflectors. The clients are unaware that they are members of a routereflection cluster. All members of the cluster must be in the same AS. The cluster ID can beany number from 1 – 4294967295, or an IP address. The default is the router ID.NOTEIf the cluster contains more than one route reflector, you need to configure the same cluster IDon all the route reflectors in the cluster. The cluster ID helps route reflectors avoid loops withinthe cluster.• A route reflector is an IGP router configured to send BGP route information to all the clients(other BGP4 routers) within the cluster. Route reflection is enabled on all Brocade BGP4routers by default but does not take effect unless you add route reflector clients to the router.
