Allied Telesis AT-WR4500 Dhcp Alert, Dhcp Option, Submenu level /ip dhcp-server alert, Host-Name

AT-WR4500 Series - IEEE 802.11abgh Outdoor Wireless Routers	123
RouterOS v3 Configuration and User Guide

Example

To assign 10.5.2.100 static IP address for the existing DHCP client (shown in the lease table as item #0):

[admin@AT-WR4562] ip dhcp-server		lease> print
Flags: X - disabled, R - radius,		D - dynamic, B - blocked
# ADDRESS	MAC-ADDRESS	HOST-NAME	SERVER RATE-LIMIT STATUS

0	D	10.5.2.90	00:04:EA:C6:0E:40	switch	bound
1	D	10.5.2.91	00:04:EA:99:63:C0	switch	bound

[admin@AT-WR4562] ip dhcp-server		lease> add copy-from=0 address=10.5.2.100
[admin@AT-WR4562] ip dhcp-server		lease> print
Flags: X - disabled, R - radius,		D - dynamic, B - blocked
# ADDRESS	MAC-ADDRESS	HOST-NAME	SERVER RATE-LIMIT STATUS

0	D 10.5.2.91	00:04:EA:99:63:C0	switch	bound
1	10.5.2.100	00:04:EA:C6:0E:40	switch	bound
[admin@AT-WR4562] ip dhcp-server lease>

6.1.7 DHCP Alert

Submenu level: /ip dhcp-server alert

Description

To find any rogue DHCP servers as soon as they appear in your network, DHCP Alert tool can be used. It will monitor ethernet for all DHCP replies and check, whether this reply comes from a valid DHCP server. If reply from unknown DHCP server is detected, alert gets triggered:

[admin@AT-WR4562] ip dhcp-server alert>/log print

00:34:23 dhcp,critical,error,warning,info,debug dhcp alert on Public: discovered unknown dhcp server, mac 00:02:29:60:36:E7, ip 10.5.8.236

[admin@AT-WR4562] ip dhcp-server alert>

When the system alerts about a rogue DHCP server, it can execute a custom script.

As DHCP replies can be unicast, rogue dhcp detector may not receive any offer to other dhcp clients at all. To deal with this, rogue dhcp server acts as a dhcp client as well - it sends out dhcp discover requests once a minute

Property Description

alert-timeout (none/time; default: none) - time, after which alert will be forgotten. If after that time the same server will be detected, new alert will be generated

none - infinite time

interface (name) - interface, on which to run rogue DHCP server finder

invalid-server (read-only: text) - list of MAC addresses of detected unknown DHCP servers. Server is removed from this list after alert-timeout

on-alert (text) - script to run, when an unknown DHCP server is detected valid-server (text) - list of MAC addresses of valid DHCP servers

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All alerts on an interface can be cleared at any time using command: /ip dhcp-server alert reset- alert <interface>

Note, that e-mail can be sent, using /system logging action add target=email

6.1.8 DHCP Option

Submenu level: /ip dhcp-server option

Description

With help of DHCP Option, it is possible to define additional custom options for DHCP Server to advertise..