Configuration Guide User guide

FastIron Configuration Guide 957
53-1002494-02
Basic IP parameters and defaults – Layer 3 Switches
Maximum
Transmission
Unit (MTU)
The maximum length an Ethernet packet can be
without being fragmented.
1500 bytes for Ethernet
II encapsulation
1492 bytes for SNAP
encapsulation
page 974
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
MAC address in an ARP reply.
Enabled page 981
ARP rate
limiting
Lets you specify a maximum number of ARP packets
the device will accept each second. If the device
receives more ARP packets than you specify, the
device drops additional ARP packets for the
remainder of the one-second interval.
Disabled page 982
ARP age The amount of time the device keeps a MAC address
learned through ARP in the device 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.
NOTE: You also can change the ARP age on an
individual interface basis. Refer to Table 165
on page 959.
Ten minutes page 983
Proxy ARP An IP mechanism a router can use to answer an ARP
request on behalf of a host, by replying with the
router own MAC address instead of the host.
Disabled page 983
Static ARP
entries
An ARP entry you place in the static ARP table. Static
entries do not age out.
No entries page 985
Time to Live
(TTL)
The maximum number of routers (hops) through
which a packet can pass before being discarded.
Each router decreases a packet 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 page 987
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.
Refer to Table 165 on page 959.
Disabled page 987
Directed
broadcast
mode
The packet format the router treats as a directed
broadcast. The following formats can be directed
broadcast:
• All ones in the host portion of the packet
destination address.
• All zeroes in the host portion of the packet
destination address.
All ones
NOTE: If you enable
all-zeroes
directed
broadcasts,
all-ones directed
broadcasts
remain enabled.
page 988
TABLE 164 IP global parameters – Layer 3 Switches (Continued)
Parameter Description Default For more
information