Product guide

IP Routing Features
Overview of IP Routing
IP Global Parameters for Routing Switches
The following table lists the IP global parameters and the page where you can
find more information about each parameter.
Table 3-1. IP Global Parameters for Routing Switches
Parameter Description Default See page
Address
Resolution
Protocol
(ARP)
A standard IP mechanism that routers use to learn
the Media Access Control (MAC) address of a
device on the network. The router sends the IP
address of a device in the ARP request and receives
the device’s MAC address in an ARP reply.
Enabled 3-10
ARP age The amount of time the device keeps a MAC address
learned through ARP in the device’s ARP cache. The
device resets the timer to zero each time the ARP
entry is refreshed and removes the entry if the timer
reaches the ARP age.
Five minutes not configurable
Proxy ARP An IP mechanism a router can use to answer an ARP
request on behalf of a host, by replying with the
router’s own MAC address instead of the host’s.
Disabled 3-12
Time to Live
(TTL)
The maximum number of routers (hops) through
which a packet can pass before being discarded.
Each router decreases a packet’s TTL by 1 before
forwarding the packet. If decreasing the TTL causes
the TTL to be 0, the router drops the packet instead
of forwarding it.
64 hops Refer to the
chapter titled
“Configuring IP
Addressing” in
the Management
and Configuration
Guide.
Directed
broadcast
forwarding
A directed broadcast is a packet containing all ones
(or in some cases, all zeros) in the host portion of the
destination IP address. When a router forwards
such a broadcast, it sends a copy of the packet out
each of its enabled IP interfaces.
Note: You also can enable or disable this parameter
on an individual interface basis. See table 3-2 on
page 3-9.
Disabled 3-13
3-7