Syed Jahanzaib Personal Blog to Share Knowledge !

February 26, 2018

Renew DHCP lease if Gateway not responding

Filed under: Mikrotik Related — Tags: , , — Syed Jahanzaib / Pinochio~:) @ 8:49 AM


Nothing Fancy , just short notes for script command reference purposes!

Following is a very simple 2 minutes instant cooked noddle type script. It will simply check the gateway status acquired by the dhcp-client using  ARP ping, , if it fails, then it will simply try to renew the ip by release/renew. Its very basic level, but its interesting to see how Mikrotik can really help you in day to day task by facilitated with the Tik level scripting !

Syed Jahanzaib

# Mikrotik Script - Tested with 5.x
# Script to check default gateway acquired by dhcp client on specific interface,
# Lot of room for improvements and modification but following was enough for some particular task,
# You can add BOUND status as well too, but i wanted this particular checking, you can add whatever you like
# Syed Jahanzaib == aacable AT hotmail DOT com - https:// aacable DOT wordpress DOT com
# Feb,2018
# Setting Variables

# Set Interface name which will get DHCP ip , This is the only option you may need to modify
:local INTERFACE "wan1"

# Number of Ping Count, how many times mikrotik should ping the target device
:local PINGCOUNT "5"

# Ping threshold, how many values should set alert, like if 5 out of 5 goes out
:local PINGTS "5"

:local i 0;
#:local i value=0;
:local F 0;
:local date;
:local time;

:log info "Checking default gateway for $INTERFACE interfaces."
:local DHCPGW [ /ip dhcp-client get [/ip dhcp-client find where interface=$INTERFACE ] gateway ]

# IF there is no default gateway on dhcpclient interface or if interface is disabled, then error
:if ([:len $DHCPGW] = 0) do={
:log error "No DEFAULT gateway found on $INTERFACE interface @ $date $time ..."
# Try to renew ip
/ip dhcp-client release $INTERFACE
/ip dhcp-client renew $INTERFACE
# Exit the script without further process ... I found this recently because in mikrotik there is no EXIT 1
error :error

# PING host $PINGCOUNT times
:for i from=1 to=$PINGCOUNT do={
:if ([/ping arp-ping=yes interface=$INTERFACE $DHCPGW count=1]=0) do={:set F ($F + 1)}
:delay 1;

# If no ping found then give error and do action
:if (($F=$PINGTS)) do={
:log error "PING to $DHCPGW via $INTERFACE is DOWN! @ $date $time "

# Take action if unable to ping gateway
/ip dhcp-client release $INTERFACE
/ip dhcp-client renew $INTERFACE
} else={
:log warning "PING to $DHCPGW via $INTERFACE is UP! @ $date $time "

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