MIB_IPFORWARDROW structure (ipmib.h)
The MIB_IPFORWARDROW structure contains information that describes an IPv4 network route.
Syntax
typedef struct _MIB_IPFORWARDROW {
DWORD dwForwardDest;
DWORD dwForwardMask;
DWORD dwForwardPolicy;
DWORD dwForwardNextHop;
IF_INDEX dwForwardIfIndex;
union {
DWORD dwForwardType;
MIB_IPFORWARD_TYPE ForwardType;
};
union {
DWORD dwForwardProto;
MIB_IPFORWARD_PROTO ForwardProto;
};
DWORD dwForwardAge;
DWORD dwForwardNextHopAS;
DWORD dwForwardMetric1;
DWORD dwForwardMetric2;
DWORD dwForwardMetric3;
DWORD dwForwardMetric4;
DWORD dwForwardMetric5;
} MIB_IPFORWARDROW, *PMIB_IPFORWARDROW;
Members
dwForwardDest
Type: DWORD
The destination IPv4 address of the route. An entry with a IPv4 address of 0.0.0.0 is considered a default route. This member cannot be set to a multicast (class D) IPv4 address.
dwForwardMask
Type: DWORD
The IPv4 subnet mask to use with the destination IPv4 address before being compared to the value in the dwForwardDest member.
The dwForwardMask value should be applied to the destination IPv4 address (logical and operation) before a comparison with the value in the dwForwardDest member.
dwForwardPolicy
Type: DWORD
The set of conditions that would cause the selection of a multi-path route (the set of next hops for a given destination). This member is typically in IP TOS format. This encoding of this member is described in RFC 1354. For more information, see http://www.ietf.org/rfc/rfc1354.txt.
dwForwardNextHop
Type: DWORD
For remote routes, the IPv4 address of the next system en route. Otherwise, this member should be an IPv4 address of 0.0.0.0.
dwForwardIfIndex
Type: DWORD
The index of the local interface through which the next hop of this route should be reached.
dwForwardType
Type: DWORD
The route type as described in RFC 1354. For more information, see http://www.ietf.org/rfc/rfc1354.txt.
This member can be one of the values defined in the Iprtmib.h header file.
On Windows Vista and later, the header files were reorganized and this member can be one of the values from the MIB_IPFORWARD_TYPE enumeration type defined in the Ipmib.h header file. Note that the Ipmib.h header is automatically included by the Iprtrmib.h header file which is automatically included by the Iphlpapi.h header. The Iprtrmib.h and Ipmib.h header files should never be used directly.
The following list shows the possible values for this member.
ForwardType
dwForwardProto
Type: DWORD
The protocol or routing mechanism that generated the route as described in RFC 1354. For more information, see http://www.ietf.org/rfc/rfc1354.txt. See Protocol Identifiers for a list of possible protocol identifiers used by routing protocols.
This member can be one of the values defined in the Iprtmib.h header file. The values for this member can be one of the MIB_IPPROTO_xxx values defined in the Iprtmib.h header file or one of the PROTO_IP_xxx values defined in the routprot.h header file since these values are the same.
On Windows Vista and later, the header files were reorganized and this member can be one of the values defined in the Nldef.h header file. Note that the Nldef.h header is automatically included by the Ipmib.h header file which is automatically included by the Iprtrmib.h header. The Iphlpapi.h header automatically includes the Iprtrmib.h header file. The Iprtrmib.h, Ipmib.h, and Nldef.h header files should never be used directly.
The following list shows the possible values for this member.
| Value | Meaning |
|---|---|
|
Some other protocol not specified in RFC 1354. |
|
A local interface. |
|
A static route. This value is used to identify route information for IP routing set through network management such as the Dynamic Host Configuration Protocol (DCHP), the Simple Network Management Protocol (SNMP), or by calls to the CreateIpForwardEntry, DeleteIpForwardEntry, or SetIpForwardEntry functions. |
|
The result of ICMP redirect. |
|
The Exterior Gateway Protocol (EGP), a dynamic routing protocol. |
|
The Gateway-to-Gateway Protocol (GGP), a dynamic routing protocol. |
|
The Hellospeak protocol, a dynamic routing protocol. This is a historical entry no longer in use and was an early routing protocol used by the original ARPANET routers that ran special software called the Fuzzball routing protocol, sometimes called Hellospeak, as described in RFC 891 and RFC 1305. For more information, see http://www.ietf.org/rfc/rfc891.txt and http://www.ietf.org/rfc/rfc1305.txt. |
|
The Berkeley Routing Information Protocol (RIP) or RIP-II, a dynamic routing protocol. |
|
The Intermediate System-to-Intermediate System (IS-IS) protocol, a dynamic routing protocol. The IS-IS protocol was developed for use in the Open Systems Interconnection (OSI) protocol suite. |
|
The End System-to-Intermediate System (ES-IS) protocol, a dynamic routing protocol. The ES-IS protocol was developed for use in the Open Systems Interconnection (OSI) protocol suite. |
|
The Cisco Interior Gateway Routing Protocol (IGRP), a dynamic routing protocol. |
|
The Bolt, Beranek, and Newman (BBN) Interior Gateway Protocol (IGP) that used the Shortest Path First (SPF) algorithm. This was an early dynamic routing protocol. |
|
The Open Shortest Path First (OSPF) protocol, a dynamic routing protocol. |
|
The Border Gateway Protocol (BGP), a dynamic routing protocol. |
|
A Windows specific entry added originally by a routing protocol, but which is now static. |
|
A Windows specific entry added as a static route from the routing user interface or a routing command. |
|
A Windows specific entry added as a static route from the routing user interface or a routing command, except these routes do not cause Dial On Demand (DOD). |
ForwardProto
dwForwardAge
Type: DWORD
The number of seconds since the route was added or modified in the network routing table.
dwForwardNextHopAS
Type: DWORD
The autonomous system number of the next hop. When this member is unknown or not relevant to the protocol or routing mechanism specified in dwForwardProto, this value should be set to zero. This value is documented in RFC 1354. For more information, see http://www.ietf.org/rfc/rfc1354.txt
dwForwardMetric1
Type: DWORD
The primary routing metric value for this route. The semantics of this metric are determined by the routing protocol specified in the dwForwardProto member. If this metric is not used, its value should be set to -1. This value is documented in in RFC 1354. For more information, see http://www.ietf.org/rfc/rfc1354.txt
dwForwardMetric2
Type: DWORD
An alternate routing metric value for this route. The semantics of this metric are determined by the routing protocol specified in the dwForwardProto member. If this metric is not used, its value should be set to -1. This value is documented in RFC 1354. For more information, see http://www.ietf.org/rfc/rfc1354.txt
dwForwardMetric3
Type: DWORD
An alternate routing metric value for this route. The semantics of this metric are determined by the routing protocol specified in the dwForwardProto member. If this metric is not used, its value should be set to -1. This value is documented in RFC 1354. For more information, see http://www.ietf.org/rfc/rfc1354.txt
dwForwardMetric4
Type: DWORD
An alternate routing metric value for this route. The semantics of this metric are determined by the routing protocol specified in the dwForwardProto member. If this metric is not used, its value should be set to -1. This value is documented in RFC 1354. For more information, see http://www.ietf.org/rfc/rfc1354.txt
dwForwardMetric5
Type: DWORD
An alternate routing metric value for this route. The semantics of this metric are determined by the routing protocol specified in the dwForwardProto member. If this metric is not used, its value should be set to -1. This value is documented in RFC 1354. For more information, see http://www.ietf.org/rfc/rfc1354.txt
Remarks
The GetIpForwardTable function enumerates the IPv4 route entries on a local system and returns this information in a MIB_IPFORWARDTABLE structure that contains an array of MIB_IPFORWARDROW structure entries.
The dwForwardDest, dwForwardMask, and dwForwardNextHop members of the MIB_IPFORWARDROW structure represent IPv4 addresses in network byte order.
The dwForwardProto member of the MIB_IPFORWARDROW structure specifies the protocol or routing mechanism that generated the route. Routing protocol identifiers are used to identify route information for the specified routing protocol. For example, MIB_IPPROTO_NETMGMT is used to identify route information for IP routing set through network management such as the Dynamic Host Configuration Protocol (DCHP), the Simple Network Management Protocol (SNMP), or by calls to the CreateIpForwardEntry, DeleteIpForwardEntry , or SetIpForwardEntry functions. See Protocol Identifiers for a list of possible protocols and routing mechanisms.
An IPv4 address of 0.0.0.0 in the dwForwardDest member of the MIB_IPFORWARDROW structure is considered a default route. The MIB_IPFORWARDTABLE may contain multiple MIB_IPFORWARDROW entries with the dwForwardDest member set to 0.0.0.0 when there are multiple network adapters installed.
When dwForwardAge is set to INFINITE, the route will not be removed based on a timeout
value. Any other value for dwForwardAge specifies the number of seconds since the route was added or modified in the network routing table.
On Windows Server 2003 or Windows 2000 Server when the Routing and Remote Access Service (RRAS) is running, the MIB_IPFORWARDROW entries returned have the dwForwardType and dwForwardAge members set to zero.
On Windows Vista and Windows Server 2008, the route metric specified in the dwForwardMetric1 member of the MIB_IPFORWARDROW structure represents a combination of the route metric added to the interface metric specified in the Metric member of the MIB_IPINTERFACE_ROW structure of the associated interface. So the dwForwardMetric1 member of the MIB_IPFORWARDROW structure should be equal to or greater than Metric member of the associated MIB_IPINTERFACE_ROW structure. If an application would like to set the route metric to 0, then the dwForwardMetric1 member of the MIB_IPFORWARDROW structure should be set equal to the value of the interface metric specified in the Metric member of the associated MIB_IPINTERFACE_ROW structure. An application can retrieve the interface metric by calling the GetIpInterfaceEntry function.
A number of members of the MIB_IPFORWARDROW structure are not currently used by IPv4 routing. These members include dwForwardPolicy, dwForwardNextHopAS, dwForwardMetric2, dwForwardMetric3, dwForwardMetric4, and dwForwardMetric5.
On the Microsoft Windows Software Development Kit (SDK) released for Windows Vista and later, the organization of header files has changed. This structure is defined in the Ipmib.h header file, not in the Iprtrmib.h header file. Note that the Ipmib.h header file is automatically included in Iprtrmib.h, which is automatically included in the Iphlpapi.h header file. The Ipmib.h and Iprtrmib.h header files should never be used directly.
Examples
To view an example that retrieves the MIB_IPFORWARDTABLE structure and then prints out the MIB_IPFORWARDROW structure entries in this table, see the GetIpForwardTable function.
Requirements
| Requirement | Value |
|---|---|
| Minimum supported client | Windows 2000 Professional [desktop apps only] |
| Minimum supported server | Windows 2000 Server [desktop apps only] |
| Header | ipmib.h (include Iphlpapi.h) |
See also
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