Product Documentation

DHCP Server and DHCP Relay Agent

Aug 09, 2017

NetScaler SD-WAN introduces the ability to use Standard or Enterprise Edition appliances  as  either  DHCP  Servers  or  DHCP  Relay  agents.  You can configure  your appliance  to  issue  IP addresses  using DHCP  or  forward  DHCP  packets  between  clients  and  servers.  

Note

  • DHCP Server supports only IP Pool based address assignment.
  • DHCP Relay does not support multiple DHCP Server IP address assignment.

How To Enable DHCP Server

NetScaler SD-WAN appliances can be configured as DHCP server that assigns and manages IP addresses from specified address pools within the network to DHCP clients. The DHCP server can be configured to assign additional parameters such as the IP address of the Domain Name System (DNS) server and the default router. DHCP server accepts address assignment requests and renewals. The DHCP server also accepts broadcasts from locally attached LAN segments or from DHCP requests that have been forwarded by other DHCP relay agents within the network.

To enable DHCP server:

     1. Navigate to Configuration Appliance Settings →   Network Adapters. In the Network Adapters page, look for the Management Interface DHCP Server pane.

     2. Click  the  Enable  DHCP  Server  checkbox  to  start  the  server,  then enter  the  Lease  Time  (in  minutes),  the  Domain  Name,  and  define  the  IP  Address  range  by  entering  a  Start  IP  Address  and  an  End  IP  Address.      

Note

The server IP address pool should be within the management network.

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     3. Click the Change Settings button to finish configuring the DHCP Server.

Note

If  you  plan  to  use  DHCP  Server  on  a   NetScaler SD-WAN  Appliance  configured  for  High  Availability  (HA),  do  not configure  the  service  on  both  the  Active  and  Standby  appliance.  Doing  so  will  lead  to  duplicate  IP addresses  on  the  defined  management  network.  

     4. Click Show Client to view the current DHCP clients, and click Clear Clients to release the DHCP Client leases.

How To Enable DHCP Relay

A DHCP relay agent is a host or router that forwards DHCP packets between clients and servers. Network  administrators  can  use  the  DHCP  Relay  service  on  the  management  port  of  the SD-WAN (Standard or Enterprise Editions)  appliances to  relay  requests  and  replies  between  local  DHCP  Clients  and  a  remote  DHCP  Server.  This  allows  local hosts  to  acquire  dynamic  IP  addresses  from  the  remote  DHCP  Server. Relay agent receives DHCP messages and generates a new DHCP message to send out on another interface. 

To enable DHCP relay service:

     1. Navigate to Configuration  Appliance SettingsNetwork Adapters. In the Network Adapters page, look for the Management Interface DHCP Relay pane.

     2. Click the Enable DHCP Relay checkbox to enable the service.  Enter  the  DHCP   Server  IP  Address  and  click  the  Change  Settings  button  to  begin  using  your  appliance  as  a  DHCP  Relay Agent.  

Note

If  you  plan  to  use  DHCP  Relay service on an appliance  configured  for  High  Availability  (HA),  do  not configure  the  service  on  both  the  Active  and  Standby  appliances.  Doing  so  will  lead  to  duplicate  IP addresses  on  the  defined  management  network.  

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How To Monitor DHCP Client WAN Links

The runtime Virtual IP address, Subnet Mask, and Gateway settings are logged and archived in a log file called “CBVW_ip_learned.log”.  Events are generated when Dynamic Virtual IPs are learned, released, or expired, and when there is a communication issue with the learned Gateway or DHCP server; or when duplicate IP addresses are detected in the archived log file. If duplicate IPs are detected at a site, Dynamic Virtual IP addresses are released and renewed until all Virtual Interfaces at the site obtain unique Virtual IP addresses. 

To monitor DHCP client WAN links:

     1.  In the Virtual WANEnable/Disable/Purge Flows page, the DHCP Client WAN Links table provides the status of learned IPs.

     2.  You can request to renew the IP, which refreshes the lease time. You can also choose to Release Renew, which will issue a new IP address with a new lease.  

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