The following variables are usable inside of the DHCP-Server script tab.
The DHCP server script runs every time there is a new lease, or a lease expires. Doesn’t look to run when static leases renew.
https://wiki.mikrotik.com/wiki/Manual:IP/DHCP_Server#General
You can find detailed info here. https://wiki.wireshark.org/DHCP
But you should be able to filter out the DHCP request with either
dhcp
or
bootp
ip.addr == 192.168.1.1
eth.dst == 01:00:5e:7f:ff:fa
Wireshark has a robust set of options for filtering items.
From the Packet Details pane you can select any piece of information you want to filter, right click -> Apply As Filter -> Selected
You can also copy it and then past it in the filter bar. Right click -> Copy -> As Filter
Sometimes it is nice to have a list of just the IP addresses and the hostname or mac address. Can be especially helpful when you are trying to get a list of devices to do a bulk update in LibreNMS. Helpful LibreNMS links for renaming and showing down devices
we are going to run the command to pull the DHCP information and then use Unix utilities to parse the data out.
Replace dhcp8 with the correct dhcp server in the mikrotik.
First, SSH into your Mikrotik router.
ssh user@mikrotik
Next we’ll want to go to the ip dhcp-server lease directory
/ip dhcp-server lease
Now we can run the following command to loop through and pull out all the info we need.
You can change the info like “mac-address” for something like “status”. You can use Tab to see what options are available. Just delete mac-address and hit tab twice.
:foreach i in=[find] do={ :put ([get $i address].",".[get $i mac-address].",".[get $i server].",".[get $i host-name ])}
Found the above helpful info from the following pdf file.
https://mum.mikrotik.com/presentations/PH18/presentation_5113_1516612695.pdf
We can use the the built in esxcli command to change the IP address for a server
First we need to get the interface name. We can get the info with the following command.
esxcli network ip interface ipv4 get
Name IPv4 Address IPv4 Netmas IPv4 Broadcast Address Type DHCP DNS
---- ------------ ------------- -------------- ------------ --------
vmk0 192.168.0.4 255.255.255.0 192.168.0.0 STATIC falseThe text in bold is our interface name.
Set the interface to pull DHCP
The following command will set the interface to use DHCP. If your interface name is different, then you will want to change that.
esxcli network ip interface ipv4 set -i vmk0 -t dhcp
Set a static IP
We can set a static IP address with the following command. Change the IP and Subnet for the appropriate IP address and Subnet.
esxcli network ip interface ipv4 set -i -I IP -N Subnet vmk0 -t static
Changes take affect immediately so you’ll need to re ssh into the server.
http://virtuallystable.com/2019/08/14/how-to-change-the-ip-address-of-an-esxi-host-via-esx-cli/
Replace ens160 with the connection name. “vmcli con show”
sudo nmcli connection mod ens160 ipv4.method auto
Should be able to restart the networking service or reboot the server
https://wiki.mikrotik.com/wiki/Manual:Interface/VLAN
VLAN successfully passes through regular Ethernet bridges
https://wiki.mikrotik.com/wiki/Manual:Basic_VLAN_switching
https://wiki.mikrotik.com/wiki/Manual:Layer2_misconfiguration
DHCP offering lease without success issue with Mikrotik on the far side of Ubiquiti device.
Make sure that radio does not have the VLAN configured on just the WAN interface. Easiest way would be to put it in bridge mode and use the management VLAN.
The UniFi cameras are different then the AirMax line in how the configuration works. There is a “/tmp/system.cfg” file, but it does not contain most of the configuration option. In the default directory there are some files which appear to handle the device configuration.
The network configuration file is “ubnt_networkd.conf”
Edit the file by opening it up in vi or a different text editor.
{
"cfgver": 2,
"dhcp": {
"fallbackIP": "192.168.1.20",
"fallbackNetmask": "255.255.255.0",
"status": 0 <-- 0=Static 1=DHCP
},
"dns": {
"ns1": {
"ip": "8.8.8.8",
"status": 1
},
"ns2": {
"ip": "4.2.2.2",
"status": 1
}
},
"routes": {
"gateway": "192.168.5.1"
},
"statik": {
"ip": "192.168.5.11",
"netmask": "255.255.255.0"
}
}
If you want to set the static address, you should be able to edit the settings in this config and leave DHCP status disabled.
To set the Camera to use DHCP, under dhcp change “”status”: 0″ to “”status”: 1″
{
"cfgver": 2,
"dhcp": {
"fallbackIP": "192.168.1.20",
"fallbackNetmask": "255.255.255.0",
"status": 1
},
"dns": {
"ns1": {
"ip": "8.8.8.8",
"status": 1
},
"ns2": {
"ip": "4.2.2.2",
"status": 1
}
},
"routes": {
"gateway": "192.168.5.1"
},
"statik": {
"ip": "192.168.5.11",
"netmask": "255.255.255.0"
}
}
After the settings are applied the camera will use use DHCP regardless of the statik ip settings.
Use the following command to write the changes to persistent storage
ubnt_cmd_persist.sh
And reboot the camera.
reboot
Camera should pull a DHCP address when it boots up
Edit the “/tmp/system.cfg”
Change the line that contains “dhcpc.status=disabled” to
dhcpc.status=enabled
add the following lines
dhcpc.1.devname=br0 dhcpc.1.fallback=192.168.1.20 dhcpc.1.fallback_netmask=255.255.255.0 dhcpc.1.status=enabled
Save and exit and save changes
/usr/etc/rc.d/rc.softrestart save
Log into the GUI and verify everything looks correct. Under the network tab it was still showing that it had a static address, although it pulled a DHCP IP.
In Linux you can send signals to a process id to trigger actions for the program. Useful scenario for this is to renew an IP address on a device that uses udhcpc. You should be able to change udhcpc for other programs, you’ll just need to read the help for that specific program.
In the udhcpc help it says
Signals:
USR1 Renew lease
USR2 Release lease
But how do we send those signals to udhcpc? Answer, use the kill command.
kill: kill [-s sigspec | -n signum | -sigspec] pid | jobspec … or kill -l [sigspec]
Send a signal to a job.
Send the processes identified by PID or JOBSPEC the signal named by SIGSPEC or SIGNUM. If neither SIGSPEC nor SIGNUM is present, then SIGTERM is assumed.
Options:
-s sig SIG is a signal name
-n sig SIG is a signal number
-l list the signal names; if arguments follow `-l' they are
assumed to be signal numbers for which names should be listed
-L synonym for -l
Kill is a shell builtin for two reasons: it allows job IDs to be used instead of process IDs, and allows processes to be killed if the limit on processes that you can create is reached.
Exit Status:
Returns success unless an invalid option is given or an error occurs.
We see from above that we can pass a signal name in using the -s option.
So to send USR1 signal to udhcp we do the following
kill -s USR1 pid_of_udhcpc
Replace pid_of_udhcpc with the actual pid or use the following command to find the pid
kill -s USR1 $(pgrep udhcpc)
“pgrep udhcpc” prints the pid of the searched for process.
Helpful links
https://www.thegeekstuff.com/2011/02/send-signal-to-process/
https://www.linux.org/threads/kill-signals-and-commands-revised.11625/
AirOS uses udhcpc for the DHCP client on Ubiquiti Radios. To renew the DHCP address you can kill the udhcpc process and it’ll automatically restart and get a new address.
Renew DHCP lease
Kill udhcpc with the following command.
killall udhcpc
Other info
Print info about the DHCP lease. May need to change “info.br1” to “info.eth0” or some other interface.
cat /etc/udhcpc/info.eth0
Example output.
XW.v6.2.0# cat /etc/udhcpc/info.br1 u_interface="br1" u_broadcast="" u_subnet="255.255.255.0" u_ip="10.93.0.10" u_router="10.93.0.1" u_dns="8.8.8.8 1.1.1.1" u_hostname="" u_serverid="10.93.0.1" u_domain="" u_leasetime=600 u_timestamp="1143249941" u_started=1142593 u_pid=936 XW.v6.2.0#
Command arguments that udhcp is run with. Info was collected by running the “ps | grep udhcp” command. Note that the interface “eth0” can be different if the device is in bridge mode.
/sbin/udhcpc -f -i eth0 -s /etc/udhcpc/udhcpc -p /var/run/udhcpc.eth0.pid -h device_name
udhcpc help output
XW.v6.2.0# udhcpc --help
BusyBox v1.24.2 (2019-07-03 11:13:35 EEST) multi-call binary.
Usage: udhcpc [-fbqvRB] [-t N] [-T SEC] [-A SEC/-n]
[-i IFACE] [-s PROG] [-p PIDFILE]
[-oC] [-r IP] [-V VENDOR] [-F NAME] [-x OPT:VAL]... [-O OPT]...
-i,--interface IFACE Interface to use (default eth0)
-s,--script PROG Run PROG at DHCP events (default /usr/share/udhcpc/default.script)
-p,--pidfile FILE Create pidfile
-B,--broadcast Request broadcast replies
-t,--retries N Send up to N discover packets (default 3)
-T,--timeout SEC Pause between packets (default 3)
-A,--tryagain SEC Wait if lease is not obtained (default 20)
-n,--now Exit if lease is not obtained
-q,--quit Exit after obtaining lease
-R,--release Release IP on exit
-f,--foreground Run in foreground
-b,--background Background if lease is not obtained
-S,--syslog Log to syslog too
-r,--request IP Request this IP address
-o,--no-default-options Don't request any options (unless -O is given)
-O,--request-option OPT Request option OPT from server (cumulative)
-x OPT:VAL Include option OPT in sent packets (cumulative)
Examples of string, numeric, and hex byte opts:
-x hostname:bbox - option 12
-x lease:3600 - option 51 (lease time)
-x 0x3d:0100BEEFC0FFEE - option 61 (client id)
-F,--fqdn NAME Ask server to update DNS mapping for NAME
-V,--vendorclass VENDOR Vendor identifier (default 'udhcp VERSION')
-C,--clientid-none Don't send MAC as client identifier
-v Verbose
Signals:
USR1 Renew lease
USR2 Release lease
XW.v6.2.0#
Note that you can also send a signal to the PID of udhcpc and have it renew the address. To do that use the following command, replacing pidofudhcpc to pid of udhcp.
kill -s USR1 pidofudhcpc
or use the following command to find the pid for you.
kill -s SIGUSR1 $(pgrep udhcpc)