This can be unhelpful in a system startup script – to disable this be- haviour, specify the -q flag. The current Agent Options draft requires that the relay agent use a maximum packet size of bytes. This can be done by specifying the -A flag, followed by the desired maximum packet size e. Or, it may dis- card it. This is mostly useful for debug- ging purposes.


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The relay agent should not relay packets received on a physical network to DHCP servers on the same physical network – if they do, the server will receive duplicate packets. As it’s scanning, if it finds a Relay Agent Information option field containing an Agent ID suboption that matches one of its IP addresses, that option is recognized as its own. The client may have filled the DHCP packet option buffer completely, in which case there theoretically isn’t any space to add Agent options.

Note that this is reasonably safe to do even if the MTU between the server and the client is less thanas long as the hosts on which the server and client are running support IP fragmentation and they should. Skip site navigation 1 Skip section navigation 2 Header And Logo. Which of these behaviours is followed by the Internet Systems Consor- tium Dhcrelau Relay Agent may be configured with the -m flag, followed by one of the four keywords specified in dhcrelaay above.

The current Agent Options draft requires dhcrely the relay agent use dhcrslay maximum packet size of bytes.


If hdcrelay packet does not have a giaddr set, the standard requires that the packet be discarded. It may forward the packet unchanged. This is useful when running dhcrelay under a debugger, or when running it out of inittab on System V systems.


This is mostly useful for debug- ging purposes. Agent option fields in responses sent dhcerlay servers to clients will be stripped be- fore forwarding such responses back to the client.

The agent option field will contain two agent options: It should be followed by the udp port number that dhcrelay should use.

It is possible for a relay agent to receive a packet which already con- tains an agent option field. Or, it may dis- card it. To learn more about In- ternet Systems Consortium, see http: If no such option is found, the relay agent can either drop the packet, or relay it anyway. This would shcrelay the case if two DHCP servers on different networks were being used to provide backup service for each other’s networks.

If no interface names are specified on the command line dhcrelay will identify all network interfaces, elimininating non-broadcast interfaces if possible, and attempt to configure each interface.


However, in some cases it may be necessary to exclude some networks; in this case, you must list all those network interfaces that should not be excluded using the -i flag. When a query is received from a client, dhcrelay forwards it to the list of DHCP servers specified on the command line.

RPM resource dhcrelay

In general, it must listen not only on those network interfaces to which clients are attached, but also on those network interfaces to which the server or the router that reaches the server is attached. When dbcrelay relay dhcfelay receives a reply from a server that it’s supposed to forward to a client, and Relay Agent Information option processing is enabled, the relay agent scans the packet for Relay Agent Informa- tion options and removes them.


Want to link to this manual page? It may replace the existing agent option field. Dhcrelay will normally print its network configuration on startup. When forwarding packets, dhcrelay discards packets which have reached a hop count of The client supports inclusion of a Remote ID suboption as well, but this is not used by vhcrelay. The -i flag can be used to specify the network interfaces on which the relay agent should listen.

FreeBSD Manual Pages

If giaddr is set, the server may handle the situation in one of four ways: If a lower or higher threshold up to is de- sired, depending on your environment, you can specify the max hop count threshold as a number following the -c option. This can be unhelpful in a system startup script – to disable this be- haviour, specify the -q flag.

To learn more about Vixie Enterprises, dhcreoay http: In order to fix this, however, the relay agent needs to be able to learn about the network topology, which requires that it have a configuration file.