Netgear M5300-28G (GSM7228S) - ProSAFE 24-port Gigabit L2+ Managed Stackable Switch ソフトウェアガイド
Routing Commands
733
M5300, M6100, and M7100 Series ProSAFE Managed Switches
IP Helper Commands
This section describes the commands to configure and monitor the IP Helper agent. IP
Helper relays DHCP and other broadcast UDP packets from a local client to one or more
servers which are not on the same network at the client.
Helper relays DHCP and other broadcast UDP packets from a local client to one or more
servers which are not on the same network at the client.
The IP Helper feature provides a mechanism that allows a router to forward certain
configured UDP broadcast packets to a particular IP address. This allows various
applications to reach servers on nonlocal subnets, even if the application was designed to
assume a server is always on a local subnet and uses broadcast packets (with either the
limited broadcast address 255.255.255.255, or a network directed broadcast address) to
reach the server.
configured UDP broadcast packets to a particular IP address. This allows various
applications to reach servers on nonlocal subnets, even if the application was designed to
assume a server is always on a local subnet and uses broadcast packets (with either the
limited broadcast address 255.255.255.255, or a network directed broadcast address) to
reach the server.
The network administrator can configure relay entries both globally and on routing interfaces.
Each relay entry maps an ingress interface and destination UDP port number to a single IPv4
address (the helper address). The network administrator may configure multiple relay entries
for the same interface and UDP port, in which case the relay agent relays matching packets
to each server address. Interface configuration takes priority over global configuration. That
is, if a packet’s destination UDP port matches any entry on the ingress interface, the packet
is handled according to the interface configuration. If the packet does not match any entry on
the ingress interface, the packet is handled according to the global IP helper configuration.
Each relay entry maps an ingress interface and destination UDP port number to a single IPv4
address (the helper address). The network administrator may configure multiple relay entries
for the same interface and UDP port, in which case the relay agent relays matching packets
to each server address. Interface configuration takes priority over global configuration. That
is, if a packet’s destination UDP port matches any entry on the ingress interface, the packet
is handled according to the interface configuration. If the packet does not match any entry on
the ingress interface, the packet is handled according to the global IP helper configuration.
The network administrator can configure discard relay entries, which direct the system to
discard matching packets. Discard entries are used to discard packets received on a specific
interface when those packets would otherwise be relayed according to a global relay entry.
Discard relay entries may be configured on interfaces, but are not configured globally.
discard matching packets. Discard entries are used to discard packets received on a specific
interface when those packets would otherwise be relayed according to a global relay entry.
Discard relay entries may be configured on interfaces, but are not configured globally.
In addition to configuring the server addresses, the network administrator also configures
which UDP ports are forwarded. Certain UDP port numbers can be specified by name in the
UI as a convenience, but the network administrator can configure a relay entry with any UDP
port number. The network administrator may configure relay entries that do not specify a
destination UDP port. The relay agent relays assumes these entries match packets with the
UDP destination ports listed in the following table. This is the list of default ports.
which UDP ports are forwarded. Certain UDP port numbers can be specified by name in the
UI as a convenience, but the network administrator can configure a relay entry with any UDP
port number. The network administrator may configure relay entries that do not specify a
destination UDP port. The relay agent relays assumes these entries match packets with the
UDP destination ports listed in the following table. This is the list of default ports.
Term
Definition
Maximum Hop Count
The maximum allowable relay agent hops.
Minimum Wait Time (Seconds)
The minimum wait time.
Admin Mode
Indicates whether relaying of requests is enabled or disabled.
Circuit Id Option Mode
The DHCP circuit Id option which may be enabled or disabled.