Juniper EX4600 Layer 3 Config – DHCP – Part 2

In this second part I want to review DHCP configuration on the Juniper switch. Part 1 I discussed interface related configurations; most of that stuff can be configured via UI now and CLI and/or CLI command section isn’t needed for that. (NOTE: Personally no matter how good the UI gets, I do like to know what all happens in the back end via CLI and I’d never want to lose access to the CLI).

DHCP deployments vary in networks and organizations. Depending on the requirements, some organizations with multiple sites choose to deploy DHCP centrally, some choose to utilize local servers and central servers. One very common deployment is using routers and/or L3 switches as DHCP servers.

Normally the process includes creating a DHCP scope, adding DHCP options, setting up excluded addresses and that’s it. DHCP configuration is currently not available via Mist Dashboard, so if there is a need to utilize a Juniper L3 switch as a DHCP server, some additional CLI commands are required in the UI, under “Additional CLI Commands”:

Juniper – Mist Dashboard – Additional CLI – DHCP

Sample DHCP Config – Juniper

set system services dhcp-local-server group MY_DHCP interface irb.100
set access address-assignment pool vlan100 family inet network 192.168.100.0/24
set access address-assignment pool vlan100 family inet range vlan-range-100 low 192.168.100.0 high 192.168.100.254
set access address-assignment pool vlan100 family inet excluded-range vlan-range-100  low 192.168.100.0 high 192.168.100.100
set access address-assignment pool vlan100 family inet dhcp-attribues router 192.168.100.1
set access address-assignment pool vlan100 family inet dhcp-attribues name-server 8.8.8.8

set system services dhcp-local-server group MY_DHCP interface irb.200
set access address-assignment pool vlan200 family inet network 192.168.200.0/24
set access address-assignment pool vlan100 family inet range vlan-range-200 low 192.168.200.0 high 192.168.200.254
set access address-assignment pool vlan200 family inet excluded-range vlan-range-200  low 192.168.200.0 high 192.168.200.100
set access address-assignment pool vlan200 family inet dhcp-attribues router 192.168.200.1
set access address-assignment pool vlan200 family inet dhcp-attribues name-server 8.8.8.8

List below gives a high level overview of the commands and step above.

  • Create a DHCP server group and name it “My_DHCP” in the example, assign it to the interface.
  • Define a network for the DHCP server.
  • Define and setup a DHCP range.
  • Setup excluded addresses. These can be set individually or a range.
  • Configure the default router for this DHCP scope.
  • Configure the DNS server(s).
  • That’s about it. This should take care of the basic, high level DHCP configuration on a Juniper L3 switch.

DHCP Options

DHCP options are at times needed for certain devices. Following command gives access to multiple DHCP options such as Option 43.

set access address-assignment pool vlan200 family inet dhcp-attributes option 43 _______
Juniper L3 Switch – DHCP Options

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