Description

This article provides a configuration example for DHCP relay on a SRX, where the DHCP server interface and DHCP relay interfaces are in different routing-instances.

Symptoms



Solution


Topology

DHCP ----(10.10.10.1) ge-0/0/1.0 SRX ge-0/0/0.0 (192.168.1.5)----(192.168.1.254) DHCP
Clients                                                                          Servers
    
where:
DHCP Relay interface ge-0/0/1.0 is in custom virtual router dhcp-relay and
DHCP Server interface ge-0/0/0.0 is in default routing instance.



Configuration

1. In order to make this setup work, the DHCP server connecting route and relay agent interface route must be in both routing-instances.

For example, in the above topology, the server route 192.168.1.0/24 needs to be shared with the dhcp-relay VR, and the dhcp-relay interface route 10.10.10.0/24 needs to be shared with the default routing instance.

See configuration below.


2. Also, a dummy dhcp-relay config must be added in the routing instance with the DHCP server.
If this is not configured, dhcp-relay will not be able to receive packets from the DHCP server.

set forwarding-options dhcp-relay server-group dummy-config


Complete configuration :

Configuration to share routes between VRs:

set policy-options policy-statement export_dhcp_server_route term 1 from instance master
set policy-options policy-statement export_dhcp_server_route term 1 from route-filter 192.168.1.0/24 exact
set policy-options policy-statement export_dhcp_server_route term 1 then accept
set policy-options policy-statement export_dhcp_server_route term 2 then reject
set policy-options policy-statement import_relay_route_to_server_vr term 1 from instance dhcp-relay
set policy-options policy-statement import_relay_route_to_server_vr term 1 from route-filter 10.10.10.0/24 exact
set policy-options policy-statement import_relay_route_to_server_vr term 1 then accept
set policy-options policy-statement import_relay_route_to_server_vr term 2 then reject


Configuration in dhcp-relay VR:

set routing-instances dhcp-relay instance-type virtual-router
set routing-instances dhcp-relay interface ge-0/0/1.0
set routing-instances dhcp-relay routing-options instance-import export_dhcp_server_route
set routing-instances dhcp-relay forwarding-options dhcp-relay server-group wifi-server 192.168.1.254
set routing-instances dhcp-relay forwarding-options dhcp-relay active-server-group wifi-server
set routing-instances dhcp-relay forwarding-options dhcp-relay group relay-in-vr interface ge-0/0/1.0


Dummy dhcp-relay config in DHCP server VR (in this case default routing instance):

set forwarding-options dhcp-relay server-group dummy-config
set routing-options instance-import import_relay_route_to_server_vr


Verification

1. Check the DHCP relay statistics:

root@vsrx-1# run show dhcp relay statistics routing-instance dhcp-relay
Packets dropped:
Total 0

Messages received:
BOOTREQUEST 1
DHCPDECLINE 0
DHCPDISCOVER 0
DHCPINFORM 0
DHCPRELEASE 0
DHCPREQUEST 1

Messages sent:
BOOTREPLY 1
DHCPOFFER 0
DHCPACK 1
DHCPNAK 0
DHCPFORCERENEW 0

For more information, refer to show dhcp relay statistics .


2. Check the DHCP client bindings in the routing instance:

root@vsrx-1# run show dhcp relay binding routing-instance dhcp-relay

IP address   Session Id  Hardware address   Expires   State     Interface
10.10.10.2   14          00:0c:29:e9:6d:00  86381     BOUND     ge-0/0/1.0

For more information, refer to show dhcp relay binding.



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