openstack - How to Check whether dhcp-server exists for that subnet before creating a subnet -

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i stuck neutron issue.

i have 2 nodes namely controller , compute neutron component installed in controller node. restarted dhcp, l3 agent services.

  1. we using namespaces dhcp agent.
  2. created private network specifying provider network type flat. after before creating subnet want check if dhcp-server exists subnet.

our subnet 10.88.210.0/24

try dhcp-discover

sends dhcpinform request host on udp port 67 obtain local configuration parameters without allocating new address.

dhcpinform dhcp request returns useful information dhcp server, without allocating ip address. request sends list of fields wants know (a handful default, every field if verbosity turned on), , server responds fields requested. should noted server doesn't have return every field, nor have return them in same order, or honour request @ all. linksys wrt54g, example, ignores list of requested fields , returns few standard ones. script displays every field receives.

example usage

nmap -su -p 67 --script=dhcp-discover <target>

output

interesting ports on 192.168.1.1: port   state service 67/udp open  dhcps | dhcp-discover: |   dhcp message type: dhcpack |   server identifier: 192.168.1.1 |   ip address lease time: 1 day, 0:00:00 |   subnet mask: 255.255.255.0 |   router: 192.168.1.1 |_  domain name server: 208.81.7.10, 208.81.7.14

loop through hosts in subnet until find dhcp server.

reference


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