Support Support Downloads Knowledge Base Case Manager My Juniper Community

Knowledge Base

Search our Knowledge Base sites to find answers to your questions.

Ask All Knowledge Base Sites All Knowledge Base Sites JunosE Defect (KA)Knowledge BaseSecurity AdvisoriesTechnical BulletinsTechnotes Sign in to display secure content and recently viewed articles

EX-Series Switch as a DHCP server

0

0

Article ID: KB11018 KB Last Updated: 12 Jul 2010Version: 3.0
Summary:
Configuring the EX-Series Switch as a DHCP server
Symptoms:

Solution:

Define a DHCP pool

The DHCP pool name is identified by a subnet on the EX switch, which is configured on a physical layer 3 interface or on a VLAN interface (IRB).  For example, if the switch has ports on VLAN 20, and interface VLAN 20 has IP 20.20.20.1/24, then the pool to assign IPs for this subnet will be configured as "set system services dhcp pool 20.20.20.0/24".  Alternately the IP address could also be assigned to a physical L3 interface. In either case when the switch receives DHCP DISCOVER / REQUEST packets on either the layer 2 VLAN 20 ports, or the layer 3 port with an interface IP, the switch knows to assign IPs from the pool identified by 20.20.20.0/24. This is how the switch can map DHCP requests to a specific pool.

You can create more pools for other subnets as needed.

Configure the DHCP pool parameters

Reference the DHCP pool by name and configure these parameters.
  • Address range for IP assignment
  • Lease time in seconds
  • DHCP Server Identifier
  • Gateway / Router, WINS, DNS addresses
  • DHCP Options if any, etc.

Configure L2 ports with correct VLAN assignment, or assign appropriate IP to layer 3 interface. Attach DHCP clients to those ports.

Example

[edit]
root@4200-48-2# show system services dhcp
pool 20.20.20.0/24 {
    address-range low 20.20.20.50 high 20.20.20.100;
    default-lease-time 3600;
    name-server {
        20.20.20.1;
    }
    wins-server {
        20.20.20.1;
    }
    router {
        20.20.20.1;
    }
    server-identifier 20.20.20.1;
}

[edit]
root@4200-48-2# show system services dhcp | display set
set system services dhcp pool 20.20.20.0/24 address-range low 20.20.20.50
set system services dhcp pool 20.20.20.0/24 address-range high 20.20.20.100
set system services dhcp pool 20.20.20.0/24 default-lease-time 3600
set system services dhcp pool 20.20.20.0/24 name-server 20.20.20.1
set system services dhcp pool 20.20.20.0/24 wins-server 20.20.20.1
set system services dhcp pool 20.20.20.0/24 router 20.20.20.1
set system services dhcp pool 20.20.20.0/24 server-identifier 20.20.20.1

[edit]
root@4200-48-2# show interfaces vlan.20  
family inet {
    address 20.20.20.1/24;
}

[edit]
root@4200-48-2# show interfaces ge-0/0/0
unit 0 {
    family ethernet-switching {
        vlan {
            members 20;
        }
    }
}

 
Attach a PC to ge-0/0/0 and a DHCP assignment takes place.

Verify DHCP Service

root@4200-48-2> show system services dhcp pool
Pool name           Low address      High address     Excluded addresses
20.20.20.0/24       20.20.20.50      20.20.20.100  

root@4200-48-2> show system services dhcp ?      
Possible completions:
  binding              Show DHCP client binding information
  conflict             Show DHCP address conflict
  global               Show DHCP global scope information
  pool                 Show DHCP address pool information
  statistics           Show DHCP statistics
Comment on this article > Affected Products Browse the Knowledge Base for more articles related to these product categories. Select a category to begin.

Getting Up and Running with Junos

Getting Up and Running with Junos Security Alerts and Vulnerabilities Product Alerts and Software Release Notices Problem Report (PR) Search Tool EOL Notices and Bulletins JTAC User Guide Customer Care User Guide Pathfinder SRX High Availability Configurator SRX VPN Configurator Training Courses and Videos End User Licence Agreement Global Search