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Monitor DHCP servers on a different subnet than the Orion Server with the DHCP User Experience Monitor

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Created by Aileen de Lara_ret, last modified by carolyn.mazenko on Aug 16, 2018

Views: 1,605 Votes: 2 Revisions: 11

August 16, 2018

Overview

In the DHCP User Experience Monitor, you can use the DHCP Discovery Request Type field to specify the protocol that SAM uses to detect DHCP servers: UnicastBroadcast, or Relay Agent

Environment

SAM 6.2 or later

Detail

If using the Broadcast option, the broadcast flag is set, the ciaddr (Client IP Address) is set to the local address, and the giaddr (Relay Agent IP Address) is not set. The DHCP client sends a unicast DHCP DISCOVER to the DHCP server IP address and the UDP Request Port (defaults to 67). The DHCP server then sends a broadcast DHCP Offer to theUDP Response Port (defaults to 68).

With this option, you can only monitor DHCP servers on the same subnet as the Orion server. No special configuration is required for the routers on your network.

 

If using the Unicast option, The broadcast flag is not set, the ciaddr (Client IP Address) is set to the local address, and the giaddr (Relay Agent IP Address) is not set. The DHCP client sends a unicast DHCP DISCOVER to the DHCP server IP address and the UDP Request Port (defaults to 67). The DHCP server then sends a unicast DHCP Offer to the ciaddr address and the UDP Response Port (defaults to 68).

With this option, SAM uses a unicast message for the DHCP request, and it also expects a unicast response from the DHCP server. This option can be used to monitor DHCP servers on the same subnet as the Orion server or on a different subnet.

 

To monitor DHCP servers on a different subnet than the Orion server, configure routers on the network to allow UDP packets between the Orion server and the DHCP server on selected ports, as shown in the following table:

 

No. Protocol Source 
IP
Source
Port
Target 
IP
Target 
Port
Notes
1 UDP Orion server IP 67 DHCP 
server IP
67 DHCP 
Request
2 UDP DHCP server
IP
67 Orion server IP 68 DHCP 
Offer
3 UDP Orion server IP 67 DHCP 
server IP
67 Release 
offered 
lease

 

The numbers for ports are configurable using the DHCP User Experience Monitor options.

 

If using the Relay Agent option, the broadcast flag is not set, the ciaddr (Client IP Address) is set to the local address, and the giaddr (Relay Agent IP Address) is set to the local address. The DHCP client sends a unicast DHCP DISCOVER to the DHCP server IP address and the UDP Request Port (defaults to 67). The DHCP server then sends a unicast DHCP Offer to the giaddr (Relay Agent IP Address) and the UDP Request Port(defaults to 67).

This option can be used to monitor DHCP servers on the same subnet as the Orion server or on a different subnet.

To monitor DHCP servers on a different subnet than the Orion server, configure routers on the network to allow UDP packets between the Orion server and the DHCP server on selected ports, as shown in the following table:

 

No.

Protocol

Source 
IP

Source
Port

Target 
IP

Target 
Port

Notes

1

UDP

Orion server IP

67

DHCP 
server IP

67

DHCP 
Request

2

UDP

DHCP server
IP

67

Orion server IP

67

DHCP 
Offer

3

UDP

Orion server IP

67

DHCP 
server IP

67

Release 
offered 
lease

The numbers for ports are configurable using the DHCP User Experience Monitor options.

 

 

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