Routing Commands
255
M4100 Series ProSAFE Managed Switches
ip helper-address (Global Config)
Use the Global Configuration ip helper-address command to have the switch forward
User Datagram Protocol (UDP) broadcasts received on an interface. To disable the
forwarding of broadcast packets to specific addresses, use the no form of this command.
The ip helper-address command forwards specific UDP broadcast from one interface to
another
. You can define many helper addresses but the total number of address-port pairs is
limited to 128 for the whole device. The setting of a helper address for a specific interface has
precedence over a setting of a helper address for all interfaces.
• <ip-address> is the destination broadcast or host address to be used when forwarding
UDP broadcasts.
You can specify 0.0.0.0 to indicate not to forward the UDP packet to
any host and enter
255.255.255.255 to broadcast the UDP packets to all hosts on the
target subnet.
• <dest-udp-port> is the broadcast packet destination UDP port number to forward. If
not specified, packets for the default services are forwarded to the helper address.
The
valid range is 0-65535.
• dhcp (port 67)
• domain (port 53)
• isakmp (port 500)
• mobile-ip (port 434)
• nameserver (port 42)
• netbios-dgm (port 138)
• netbios-ns (port 137)
• ntp (port 123)
• pim-auto-rp (port 496)
• rip (port 520)
• tacacs (port 49)
• tftp (port 69)
• time (port 37)
Default No helper addresses are configured.
Format ip helper-address <ip-address> [<dest-udp-port> | dhcp | domain |
isakmp | mobile-ip | nameserver | netbios-dgm | netbios-ns | ntp |
pim-auto-rip | rip | tacacs | tftp | time]
Mode Global Config
Parameter Description
<ip-address> The IPv4 unicast or directed broadcast address to which relayed UDP broadcast
packets are sent. The IP address cannot be an IP address configured on any
interface of the local router.
<dest-udp-port> A destination UDP port number from 0 to 65535.
port name options The destination UDP port may be optionally specified by its name. Whether a port is
specified by its number or its name has no effect on behavior. The names
recognized are as follows:
Other ports must be specified by number.
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