Dell PowerEdge M520 Dell Converged Enhanced Ethernet Administrator's Guide - Page 46

4 Configuring IP static routes TABLE 6 Feature IP static route features and capabilities Capability Static Routes ARPs Less than 2048, which are shared between IP address' and static routes) 1024 (due to Linux IP stack limitation) eAnvil Chip capability 12288 Anvil Chip capability 16384 Configuring IP static routes In directly attached static routes, only the output interface is specified. The destination is assumed to be directly attached to this interface, so the packet destination is used as the next-hop address. Directly attached static routes are candidates for insertion in the IPv4 routing table only if they refer to a valid IPv4 interface; that is, an interface that is both up and has IPv4 enabled on it. This configuration is not recommended because when the next hop of a static route points to an interface, the router considers each of the hosts within the range of the route to be directly connected through that interface. With this type of configuration, a router performs Address Resolution Protocol (ARP) on the Ethernet for every destination the router finds through the default route because the router considers all of these destinations as directly connected to internal 10 Gbps interface 0/1. This kind of default route, especially if it is used by a lot of packets to many different destination subnets, can cause high processor utilization and a large ARP cache. Specifying a numerical next hop on a directly connected interface prevents the router from performing ARP or each destination address. However, if the interface with the next hop goes down and the numerical next hop is reachable through a recursive route, you should specify both the next hop IP address and the interface through which the next hop should be found. NOTE By default, static routes are preferred to routes learned by routing protocols. Therefore, you can configure an administrative distance with a static route if you want the static route to be overridden by dynamic routes. For example, you could have routes installed by the Open Shortest Path First (OSPF) protocol with an administrative distance of 120. To have a static route that would be overridden by an OSPF dynamic route, specify an administrative distance greater than 120. The following example shows all destinations with address prefix 1.1.1.1/32 are directly reachable through internal 10 Gbps interface 0/1, with an administrative distance of 1. switch(config)#ip route 1.1.1.1/32 intengigabitethernet 0/1 1 NOTE Fabric OS v6.3.1_cee allows 64 ECMP routes. Once this pool is exhausted, any additional ECMP routes are automatically rejected. If one of the existing ECMP routes is deleted, previously rejected ECMP routes must be re-added manually. 28 Dell Converged Enhanced Ethernet Administrator's Guide 53-1002116-01