Difference between revisions of "ARPwatch"

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[[Main Page|Home]] > [[Rocky Linux or CentOS]] > [[Rocky Linux 9.x]] > [[Rocky 9.x Network Monitoring Tools]] > [[ARPwatch]]
[[Main Page|Home]] > [[Rocky Linux or CentOS]] > [[Rocky Linux 9.x]] > [[Rocky 9.x Network Monitoring Tools]] > [[ARPwatch]]


== Configuring Virtual Machine ==
== Create Virtual Machine ==


* Create a Rocky 9.x VM in the Vcenter
* Create a Rocky 9.x VM in the Vcenter
* Select '''All VLANs Trunk''' in Network Adapter while creating the Virtual Machine
* Select '''All VLANs Trunk''' in Network Adapter while creating the Virtual Machine


== Confugring Network Scripts ==
== Configure Network Scripts ==
 
Create Network Scripts for each Vlan as per the below article:
 
[[CentOS 8.x Configure ethernet port for 802.3 encapsulated trunk traffic communication]]
 
* Example Network script ( file name: ifcfg-ens33.99)
 
<pre>
VLAN=yes
TYPE=Vlan
PHYSDEV=ens33
VLAN_ID=99
REORDER_HDR=yes
GVRP=no
MVRP=no
HWADDR=
PROXY_METHOD=none
BROWSER_ONLY=no
BOOTPROTO=none
IPADDR=172.30.7.106
PREFIX=16
GATEWAY=172.30.0.1
DNS1=172.31.1.160
DNS2=8.8.8.8
DEFROUTE=yes
IPV4_FAILURE_FATAL=no
IPV6_DISABLED=yes
IPV6INIT=no
NAME=ens33.99
DEVICE=ens33.99
ONBOOT=yes
</pre>
 
* Restart the Network
 
<pre>
# systemctl restart NetworkManager
</pre>
 
* Remove the main interface
 
<pre>
# nmcli connection del <interface name>
</pre>
 
* Ping to gateway should work for each sub-interface
* Should be able to access the Internet
 
== Configure Postfix ==
 
Install postfix to enable the mail alerts for ARPwatch
 
Configure postfix as per the below article:
 
[[CentOS 8.x postfix send email through relay or smarthost with smtp authentication]]
 
== Configure ARPwatch ==
 
* install ARPwatch
<pre>
# dnf update
# dnf install epel-release
# dnf install arpwatch
</pre>
 
* Start the service
<pre>
# systemctl start arpwatch
# systemctl status arpwatch
</pre>
 
* Add the sub-interfaces to ARPwatch
<pre>
# arpwatch -i <sub-interface>
</pre>
 
* Restart the service
<pre>
# systemctl restart arpwatch
</pre>
 
* Check the Process to confirm that ARPwatch is running
<pre>
# ps aux | grep arpwatch
</pre>
 
* Example output
<pre>
[root@localhost ~]# ps aux | grep arpwatch
arpwatch  41710  0.0  0.3  40860  6656 ?        Ss  May13  0:21 /usr/sbin/arpwatch -u arpwatch -F -C
root      41760  0.0  0.3  40976  6024 ?        Ss  May13  0:00 arpwatch -i ens33.40
root      41763  0.0  0.4  40976  8200 ?        Ss  May13  0:01 arpwatch -i ens33.99
root      44122  0.0  0.1 221664  2176 pts/2    S+  16:45  0:00 grep --color=auto arpwatch
 
</pre>
 
* Check logs in the following file
<pre>
/var/log/messages
</pre>
 
* Example mail alert output
<pre>
hostname: <unknown>
ip address: 172.30.30.25
ethernet address: bc:24:11:48:b3:56
ethernet vendor: Proxmox Server Solutions GmbH
timestamp: Wednesday, May 14, 2025 15:46:10 +0530
</pre>
 
 
== Suppress flip flop and changed Ethernet address alerts ==
 
To suppress '''flip flop''' and '''changed Ethernet address''' alerts, we can use Postfix '''header_checks''' mechanism as a global filter.
 
* Create or edit a header checks file
 
<pre>
vim /etc/postfix/header_checks
</pre>
 
* Add rule
<pre>
/^Subject:.*flip flop/ DISCARD
/^Subject:.*changed ethernet address/ DISCARD
</pre>
 
* Enable in main.cf
<pre>
vim /etc/postfix/main.cf
</pre>
 
<pre>
header_checks = regexp:/etc/postfix/header_checks
</pre>
 
* Reload postfix
<pre>
postmap /etc/postfix/header_checks
</pre>
 
<pre>
postfix reload
</pre>
 
 
This will drop the mail at the SMTP level, before delivery.
 
 
Reference
 
* [[CentOS 8.x postfix send email through relay or smarthost with smtp authentication]]
* https://www.tecmint.com/monitor-ethernet-activity-in-linux/

Latest revision as of 12:05, 13 June 2025

Home > Rocky Linux or CentOS > Rocky Linux 9.x > Rocky 9.x Network Monitoring Tools > ARPwatch

Create Virtual Machine

  • Create a Rocky 9.x VM in the Vcenter
  • Select All VLANs Trunk in Network Adapter while creating the Virtual Machine

Configure Network Scripts

Create Network Scripts for each Vlan as per the below article:

CentOS 8.x Configure ethernet port for 802.3 encapsulated trunk traffic communication

  • Example Network script ( file name: ifcfg-ens33.99)
VLAN=yes
TYPE=Vlan
PHYSDEV=ens33
VLAN_ID=99
REORDER_HDR=yes
GVRP=no
MVRP=no
HWADDR=
PROXY_METHOD=none
BROWSER_ONLY=no
BOOTPROTO=none
IPADDR=172.30.7.106
PREFIX=16
GATEWAY=172.30.0.1
DNS1=172.31.1.160
DNS2=8.8.8.8
DEFROUTE=yes
IPV4_FAILURE_FATAL=no
IPV6_DISABLED=yes
IPV6INIT=no
NAME=ens33.99
DEVICE=ens33.99
ONBOOT=yes
  • Restart the Network
# systemctl restart NetworkManager
  • Remove the main interface
# nmcli connection del <interface name>
  • Ping to gateway should work for each sub-interface
  • Should be able to access the Internet

Configure Postfix

Install postfix to enable the mail alerts for ARPwatch

Configure postfix as per the below article:

CentOS 8.x postfix send email through relay or smarthost with smtp authentication

Configure ARPwatch

  • install ARPwatch
# dnf update
# dnf install epel-release
# dnf install arpwatch
  • Start the service
# systemctl start arpwatch
# systemctl status arpwatch
  • Add the sub-interfaces to ARPwatch
# arpwatch -i <sub-interface>
  • Restart the service
# systemctl restart arpwatch
  • Check the Process to confirm that ARPwatch is running
# ps aux | grep arpwatch
  • Example output
[root@localhost ~]# ps aux | grep arpwatch
arpwatch   41710  0.0  0.3  40860  6656 ?        Ss   May13   0:21 /usr/sbin/arpwatch -u arpwatch -F -C
root       41760  0.0  0.3  40976  6024 ?        Ss   May13   0:00 arpwatch -i ens33.40
root       41763  0.0  0.4  40976  8200 ?        Ss   May13   0:01 arpwatch -i ens33.99
root       44122  0.0  0.1 221664  2176 pts/2    S+   16:45   0:00 grep --color=auto arpwatch
  • Check logs in the following file
/var/log/messages
  • Example mail alert output
hostname: <unknown>
ip address: 172.30.30.25
ethernet address: bc:24:11:48:b3:56
ethernet vendor: Proxmox Server Solutions GmbH
timestamp: Wednesday, May 14, 2025 15:46:10 +0530


Suppress flip flop and changed Ethernet address alerts

To suppress flip flop and changed Ethernet address alerts, we can use Postfix header_checks mechanism as a global filter.

  • Create or edit a header checks file
vim /etc/postfix/header_checks
  • Add rule
/^Subject:.*flip flop/ DISCARD
/^Subject:.*changed ethernet address/ DISCARD
  • Enable in main.cf
vim /etc/postfix/main.cf

header_checks = regexp:/etc/postfix/header_checks
  • Reload postfix
postmap /etc/postfix/header_checks

postfix reload


This will drop the mail at the SMTP level, before delivery.


Reference

Retrieved from "http://www.sbarjatiya.com/notes_wiki/index.php?title=ARPwatch&oldid=8906"