Linux ISC DHCP relay

Author: ipspace

DHCP/relay/README.md

@@ -8,10 +8,12 @@ After starting the lab, the *user* device should get DHCP-assigned IP address on
 
 ## Changing Device Types
 
-This topology can be used with Cisco IOSv or Arista EOSv. To test it with other devices, add custom configuration template to `dhcp-relay` directory.
+This topology can be used with Cisco IOSv, Arista EOSv, or Linux ISC DHCP relay. To test it with other devices, add custom configuration template to `dhcp-relay` directory.
 
 The easiest way to change the device types is to edit the topology file. You could also use the **netlab up** [CLI arguments](https://netsim-tools.readthedocs.io/en/latest/netlab/up.html#usage) -- to change the DHCP relay device type, use `-s nodes.relay.device=xxx` CLI argument.
 
+To use the ISC DHCP relay, you have to add `role: router` to the  **dhcp_server** group. See the [Linux VM](linux-vm.yml)  topology for more details.
+
 ## Using Linux as the DHCP Client
 
 The default lab topology uses Cisco IOSv as the DHCP client and server. You can use a Linux VM or a Linux container as a DHCP client if you don't have access to Cisco IOSv.

DHCP/relay/dhcp-client/linux-clab.j2

@@ -18,7 +18,7 @@ SCRIPT
 #
 {% for intf in interfaces if intf.dhcp.client|default(False) %}
 ip addr flush dev {{ intf.ifname }}
-/sbin/udhcpc -S -i {{ intf.ifname }} &
+/sbin/udhcpc -S -i {{ intf.ifname }} -b &
 {% endfor %}
 
 exit 0

DHCP/relay/dhcp-relay/linux.j2

@@ -0,0 +1,12 @@
+#!/bin/bash
+#
+export DEBIAN_FRONTEND=noninteractive
+apt-get install -qq -y isc-dhcp-relay
+dhcrelay -4 {%
+   for intf in interfaces if intf.dhcp.server is defined %}
+{%   if loop.first %}
+{%     set srv = hostvars[intf.dhcp.server] %}
+{%     set ipv4 = srv.loopback.ipv4 if 'loopback' in srv else srv.interfaces[0].ipv4 %}
+{{ ipv4|ipaddr('address') }}
+{%   endif %}
+{% endfor %}

DHCP/relay/linux-vm.yml

@@ -22,7 +22,8 @@ groups:
   switch:
     members: [ relay ]
     config: [ dhcp-relay ]
-    device: iosv
+    device: linux
+    role: router
 
 nodes: [ srv, relay, user ]