How to check if ARP is enabled or not

Question

I have enabled the arp support on my dell based server running linux on it. I wanted to check that if arptables are enabled or not.

Could anyone tell me how do I check the same?

Is it enough to run arp command here?

Solution 1

The TCP/IP protocol will not work without ARP so that is always available. Normally ARP works automatically and doesn't require manual intervention.

As the other posts mention cat /proc/net/arp displays the current arp table/cache without using specific tools. You can manipulate the arp cache and static entries with the arp and ip neighbour commands as well.

arptables is a method in the Linux kernel to manage packet filtering on arp packets comparable to the iptables command that manages packet filtering on TCP and UDP packets.

As far as I know the useage of arp filtering is not the default found in most Linux distributions, although most do include the kernel support for arptables. You can typically check for kernel support with modinfo arp_tables.

If the arptables command is also installed arptables -L -n will display any/all rules that are configured.

Solution 2

ARP can be disabled on a per-interface basis. ip link show <device> will inndicate "NOARP" in if it is disabled. For example:

$ ip link show eth2
11: eth2: <BROADCAST,MULTICAST,NOARP,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP qlen 1000
    link/ether 00:0e:c6:89:b1:ac brd ff:ff:ff:ff:ff:ff`

Solution 3

You can simply Check using arp command which basically read file from /proc as below :

cat /proc/net/arp

Comments

[S edwards]

I think ´arp´ is enable on any machine having an etherent connector.

[Rahul Patil]

@Rajan if possible more details, like what was issue, what you did and what you want.

[Rajan Pathak]

I run arp command of my machine and i just see blank output there.What could I make of it?

[HBruijn]

Normally you would see at least the arp address of your default gateway, as long as there's actually network traffic. Entries in the cache expire after a couple of minutes, so if you don't have any traffic between systems on the same subnet, nor any WAN/internet traffic, the arp cache may wel be empty. Ping the default gateway and you should see an arp entry appear.