ARP cache
The ARP cache contains dynamic (learned) entries. The software places a dynamic entry in the ARP cache when
the routing switch learns a device's MAC address from an ARP request or ARP reply from the device.
The software can learn an entry when the switch or routing switch receives an ARP request from another IP
forwarding device or an ARP reply. Here is an example of a dynamic entry:
ARP cache dynamic entry
IP Address MAC Address Type Port
1 207.95.6.102 0800.5afc.ea21 Dynamic 6
Each entry contains the destination device's IP address and MAC address.
To configure other ARP parameters, see
on page 151.
IP route table
The IP route table contains routing paths to IP destinations.
NOTE:
The default gateway, which you specify when you configure the basic IP information on the switch, is
used only when routing is not enabled on the switch.
Routing paths
The IP route table can receive the routing paths from the following sources:
• Directly-connected destination, which means there are no router hops to the destination
• Static route, which is a user-configured route
• Route learned through RIP
• Route learned through OSPF
Administrative distance
The IP route table contains the best path to a destination. When the software receives paths from more than one
of the sources listed above, the software compares the administrative distance of each path and selects the path
with the lowest administrative distance. The administrative distance is a protocol-independent value from 1 to 255.
The IP route table is displayed by entering the
show ip route
command from any context level in the console
CLI. Here is an example of an entry in the IP route table:
IP route table entry
Destination Gateway VLAN Type Sub-Type Metric Di
----------------- --------------- ---- --------- ---------- -------- --
10.10.10.1/32 10.10.12.1 connected 1
Each IP route table entry contains the destination's IP address and subnet mask and the IP address of the next-
hop router interface to the destination. Each entry also indicates route type, and for OSPF routes, the subtype,
and the route's IP metric (cost). The type indicates how the IP route table received the route.
Enter the
show ip route
summary command to display the aggregate count of routes for each routing protocol.
Chapter 5 Routing Basics
145
