ip helper-address
15-16 IP Configuration
Example
This
example
shows
how
to
enable
IP
directed
broadcasts
on
VLAN
1:
G3(su)->router(Config)#interface vlan 1
G3(su)->router(Config-if(Vlan 1))#ip directed-broadcast
ip helper-address
Use
this
command
to
enable
the
DHCP/BOOTP
relay
agent
on
a
G
‐
Series
routed
interface.
Enabling
the
relay
agent
allows
forwarding
of
client
DHCP/BOOTP
requests
to
a
DHCP/BOOTP
server
that
does
not
reside
on
the
same
broadcast
domain
as
the
client.
Up
to
6
IP
helper
addresses
may
be
configured
per
interface.
The
no
form
of
this
command
disables
the
forwarding
of
UDP
datagrams
to
the
specified
address.
Syntax
ip helper-address
address
no ip helper-address
address
Parameters
Defaults
None.
Mode
Interface
configuration:
G3(su)
‐
>Router1(Config
‐
if(Vlan
1))#
Usage
When
a
host
requests
an
IP
address,
it
sends
out
a
DHCP
broadcast
packet.
Normally,
the
router
drops
all
broadcast
packets.
However,
by
executing
this
command,
you
enable
the
routed
interface
to
pass
DHCP
broadcast
frames
through,
sending
them
directly
to
the
remote
DHCP
server’s
IP
address.
The
DHCP/BOOTP
relay
agent
will
detect
DHCP/BOOTP
requests
based
on
UDP
source
and
destination
ports.
It
will
then
make
the
necessary
changes
to
the
packet
and
send
the
packet
to
the
DHCP
server.
The
changes
include:
•
Replacing
the
destination
IP
address
with
the
address
of
the
DHCP
server,
•
Replacing
the
source
IP
address
with
its
own
address
(that
is,
the
IP
address
of
the
local
routed
interface),
and
•
Within
the
BOOTP
part
of
the
packet,
changing
the
Relay
Agent
IP
address
from
0.0.0.0
to
the
address
of
the
local
routed
interface.
The
last
change
to
the
BootP
packet
“tells”
the
DHCP
server
that
it
needs
to
assign
an
IP
address
that
is
in
the
same
subnet
as
the
Relay
Agent
IP.
When
the
response
comes
from
the
server,
the
DHCP/BOOTP
relay
agent
sends
it
to
the
host.
address
Address
of
the
host
where
UDP
broadcast
packets
should
be
forwarded.
Summary of Contents for G3G170-24
Page 1: ...Enterasys G Series Ethernet Switch CLI Reference Firmware Version 1 00 xx P N 9034358 01...
Page 2: ......
Page 30: ...xxviii...
Page 100: ...set ssl 2 56 Basic Configuration...
Page 132: ...clear lldp port tx tlv 3 32 Discovery Protocol Configuration...
Page 272: ...show spantree nonforwardingreason 6 52 Spanning Tree Configuration...
Page 296: ...set garp timer 7 24 802 1Q VLAN Configuration...
Page 384: ...clear nodealias config 11 34 Logging and Network Management...
Page 438: ...Enabling Router Configuration Modes 14 4 Preparing for Router Mode...
Page 514: ...show ip pimsm staticrp 16 56 IPv4 Routing Protocol Configuration...
Page 524: ...traceroute ipv6 17 10 IPv6 Management...
Page 602: ...show ipv6 ospf virtual link 19 46 OSPFv3 Configuration...
