Configuring IP
December 2000 15 - 11
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 15-35
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 15.2 on
page 15-14.
Disabled 15-35
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’s
destination address.
• All zeroes in the host portion of the packet’s
destination address.
All ones
Note: If you enable
all-zeroes directed
broadcasts, all-ones
directed broadcasts
remain enabled.
15-37
Source-routed
packet
forwarding
A source-routed packet contains a list of IP addresses
through which the packet must pass to reach its
destination.
Enabled 15-36
ICMP Router
Discovery
Protocol (IRDP)
An IP protocol a router can use to advertise the IP
addresses of its router interfaces to directly attached
hosts. You can enable or disable the protocol, and
change the following protocol parameters:
• Forwarding method (broadcast or multicast)
• Hold time
• Maximum advertisement interval
• Minimum advertisement interval
• Router preference level
Note: You also can enable or disable IRDP and
configure the parameters on an individual interface
basis. See Table 15.2 on page 15-14.
Disabled 15-66
Reverse ARP
(RARP)
A IP mechanism a host can use to request an IP
address from a directly attached router when the host
boots.
Enabled 15-68
Static RARP
entries
An IP address you place in the RARP table for RARP
requests from hosts.
Note: You must enter the RARP entries manually.
The Layer 3 Switch does not have a mechanism for
learning or dynamically generating RARP entries.
No entries 15-69
Table 15.1: IP Global Parameters – Layer 3 Switches (Continued)
Parameter Description Default See page...
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