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IP Helper/DHCP Relay Commands
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IP Helper/DHCP Relay Commands
The IP Helper feature provides the ability for a router to forward configured
UDP broadcast packets to a particular IP address. This allows applications to
reach servers on non-local subnets. This is possible even when the application
is designed to assume a server is always on a local subnet or when the
application uses broadcast packets to reach the server (with the limited
broadcast address 255.255.255.255, or a network directed broadcast address).
Network administrators can configure relay entries 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). Multiple relay
entries may be configured 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. If the destination UDP
port for a packet 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.
Network administrators can configure discard relay entries. 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.
Additionally, administrators can configure which UDP ports are forwarded.
Certain UDP port numbers can be specified by name in the UI, but network
administrators can configure a relay entry with any UDP port number.
Administrators may configure relay entries that do not specify a destination
UDP port. The relay agent assumes that these entries match packets with the
UDP destination ports listed in Table 47-1.
Table 47-1. UDP Destination Ports
Protocol
UDP Port Number
IEN-116 Name Service
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2CSPC4.XCT-SWUM2XX1.book Page 947 Monday, October 3, 2011 11:05 AM
Summary of Contents for PowerConnect 7000 Series
Page 74: ...74 Contents 2CSPC4 XCT SWUM2XX1 book Page 74 Monday October 3 2011 11 05 AM ...
Page 164: ...164 Command Groups 2CSPC4 XCT SWUM2XX1 book Page 164 Monday October 3 2011 11 05 AM ...
Page 266: ...266 AAA Commands 2CSPC4 XCT SWUM2XX1 book Page 266 Monday October 3 2011 11 05 AM ...
Page 316: ...316 Auto VoIP Commands 2CSPC4 XCT SWUM2XX1 book Page 316 Monday October 3 2011 11 05 AM ...
Page 368: ...368 DHCP Snooping Commands 2CSPC4 XCT SWUM2XX1 book Page 368 Monday October 3 2011 11 05 AM ...
Page 454: ...454 Ethernet CFM Commands 2CSPC4 XCT SWUM2XX1 book Page 454 Monday October 3 2011 11 05 AM ...
Page 468: ...468 Green Ethernet Commands 2CSPC4 XCT SWUM2XX1 book Page 468 Monday October 3 2011 11 05 AM ...
Page 558: ...558 IP Source Guard Commands 2CSPC4 XCT SWUM2XX1 book Page 558 Monday October 3 2011 11 05 AM ...
Page 578: ...578 Link Dependency Commands 2CSPC4 XCT SWUM2XX1 book Page 578 Monday October 3 2011 11 05 AM ...
Page 606: ...606 LLDP Commands 2CSPC4 XCT SWUM2XX1 book Page 606 Monday October 3 2011 11 05 AM ...
Page 700: ...700 QoS Commands 2CSPC4 XCT SWUM2XX1 book Page 700 Monday October 3 2011 11 05 AM ...
Page 728: ...728 RADIUS Commands 2CSPC4 XCT SWUM2XX1 book Page 728 Monday October 3 2011 11 05 AM ...
Page 808: ...808 VLAN Commands 2CSPC4 XCT SWUM2XX1 book Page 808 Monday October 3 2011 11 05 AM ...
Page 814: ...814 Voice VLAN Commands 2CSPC4 XCT SWUM2XX1 book Page 814 Monday October 3 2011 11 05 AM ...
Page 848: ...848 802 1x Commands 2CSPC4 XCT SWUM2XX1 book Page 848 Monday October 3 2011 11 05 AM ...
Page 850: ...850 Layer 3 Commands 2CSPC4 XCT SWUM2XX1 book Page 850 Monday October 3 2011 11 05 AM ...
Page 912: ...912 DHCPv6 Commands 2CSPC4 XCT SWUM2XX1 book Page 912 Monday October 3 2011 11 05 AM ...
Page 920: ...920 DVMRP Commands 2CSPC4 XCT SWUM2XX1 book Page 920 Monday October 3 2011 11 05 AM ...
Page 946: ...946 IGMP Proxy Commands 2CSPC4 XCT SWUM2XX1 book Page 946 Monday October 3 2011 11 05 AM ...
Page 1062: ...1062 IPv6 Routing Commands 2CSPC4 XCT SWUM2XX1 book Page 1062 Monday October 3 2011 11 05 AM ...
Page 1174: ...1174 OSPF Commands 2CSPC4 XCT SWUM2XX1 book Page 1174 Monday October 3 2011 11 05 AM ...
Page 1234: ...1234 OSPFv3 Commands 2CSPC4 XCT SWUM2XX1 book Page 1234 Monday October 3 2011 11 05 AM ...
Page 1294: ...1294 Utility Commands 2CSPC4 XCT SWUM2XX1 book Page 1294 Monday October 3 2011 11 05 AM ...
Page 1304: ...1304 Auto Install Commands 2CSPC4 XCT SWUM2XX1 book Page 1304 Monday October 3 2011 11 05 AM ...
Page 1348: ...1348 CLI Macro Commands 2CSPC4 XCT SWUM2XX1 book Page 1348 Monday October 3 2011 11 05 AM ...
Page 1366: ...1366 Clock Commands 2CSPC4 XCT SWUM2XX1 book Page 1366 Monday October 3 2011 11 05 AM ...
Page 1478: ...1478 RMON Commands 2CSPC4 XCT SWUM2XX1 book Page 1478 Monday October 3 2011 11 05 AM ...
Page 1518: ...1518 Sflow Commands 2CSPC4 XCT SWUM2XX1 book Page 1518 Monday October 3 2011 11 05 AM ...
Page 1578: ...1578 Syslog Commands 2CSPC4 XCT SWUM2XX1 book Page 1578 Monday October 3 2011 11 05 AM ...
Page 1646: ...1646 Telnet Server Commands 2CSPC4 XCT SWUM2XX1 book Page 1646 Monday October 3 2011 11 05 AM ...
Page 1686: ...1686 Web Server Commands 2CSPC4 XCT SWUM2XX1 book Page 1686 Monday October 3 2011 11 05 AM ...
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