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28 Dell Converged Enhanced Ethernet Administrator’s Guide
53-1002116-01
Configuring IP static routes
4
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.
Static Routes Less than 2048, which are shared between IP
address’ and static routes)
ARPs 1024 (due to Linux IP stack limitation)
eAnvil Chip capability 12288
Anvil Chip capability 16384
TABLE 6 IP static route features and capabilities
Feature Capability