Linux очистить arp таблицу

NAME

arp - manipulate the system ARP cache

SYNOPSIS

arp [-vn] [-H type] [-i if] [-a] [hostname] arp [-v] [-i if] -d hostname [pub] arp [-v] [-H type] [-i if] -s hostname hw_addr [temp] arp [-v] [-H type] [-i if] -s hostname hw_addr [netmask nm] pub arp [-v] [-H type] [-i if] -Ds hostname ifname [netmask nm] pub arp [-vnD] [-H type] [-i if] -f [filename]

DESCRIPTION

Arp manipulates or displays the kernel's IPv4 network neighbour cache. It can add entries to the table, delete one or display the current content. ARP stands for Address Resolution Protocol, which is used to find the media access control address of a network neighbour for a given IPv4 Address.

MODES

arp with no mode specifier will print the current content of the table. It is possible to limit the number of entries printed, by specifying an hardware address type, interface name or host address. arp -d address will delete a ARP table entry. Root or netadmin priveledge is required to do this. The entry is found by IP address. If a hostname is given, it will be resolved before looking up the entry in the ARP table. arp -s address hw_addr is used to set up a new table entry. The format of the hw_addr parameter is dependent on the hardware class, but for most classes one can assume that the usual presentation can be used. For the Ethernet class, this is 6 bytes in hexadecimal, separated by colons. When adding proxy arp entries (that is those with the publish flag set a netmask may be specified to proxy arp for entire subnets. This is not good practice, but is supported by older kernels because it can be useful. If the temp flag is not supplied entries will be permanent stored into the ARP cache. To simplyfy setting up entries for one of your own network interfaces, you can use the arp -Ds address ifname form. In that case the hardware address is taken from the interface with the specified name.

OPTIONS

-v, --verbose Tell the user what is going on by being verbose. -n, --numeric shows numerical addresses instead of trying to determine symbolic host, port or user names. -H type, --hw-type type When setting or reading the ARP cache, this optional parameter tells arp which class of entries it should check for. The default value of this parameter is ether (i.e. hardware code 0x01 for IEEE 802.3 10Mbps Ethernet). Other values might include network technologies such as ARCnet (arcnet) , PROnet (pronet) , AX.25 (ax25) and NET/ROM (netrom). -a Use alternate BSD style output format (with no fixed columns). -D, --use-device Instead of a hw_addr, the given argument is the name of an interface. arp will use the MAC address of that interface for the table entry. This is usually the best option to set up a proxy ARP entry to yourself. -i If, --device If Select an interface. When dumping the ARP cache only entries matching the specified interface will be printed. When setting a permanent or temp ARP entry this interface will be associated with the entry; if this option is not used, the kernel will guess based on the routing table. For pub entries the specified interface is the interface on which ARP requests will be answered. NOTE: This has to be different from the interface to which the IP datagrams will be routed. NOTE: As of kernel 2.2.0 it is no longer possible to set an ARP entry for an entire subnet. Linux instead does automagic proxy arp when a route exists and it is forwarding. See arp(7) for details. Also the dontpub option which is available for delete and set operations cannot be used with 2.4 and newer kernels. -f filename, --file filename Similar to the -s option, only this time the address info is taken from file filename. This can be used if ARP entries for a lot of hosts have to be set up. The name of the data file is very often /etc/ethers, but this is not official. If no filename is specified /etc/ethers is used as default. The format of the file is simple; it only contains ASCII text lines with a hostname, and a hardware address separated by whitespace. Additionally the pub, temp and netmask flags can be used. In all places where a hostname is expected, one can also enter an IP address in dotted- decimal notation. As a special case for compatibility the order of the hostname and the hardware address can be exchanged. Each complete entry in the ARP cache will be marked with the C flag. Permanent entries are marked with M and published entries have the P flag.

EXSAMPLES

/usr/sbin/arp -i eth0 -Ds 10.0.0.2 eth1 pub This will answer ARP requests for 10.0.0.2 on eth0 with the MAC address for eth1. /usr/sbin/arp -i eth1 -d 10.0.0.1 Delete the ARP table entry for 10.0.0.1 on interface eth1. This will match published proxy ARP entries and permanent entries.

FILES

/proc/net/arp /etc/networks /etc/hosts /etc/ethers

AUTHORS

Fred N. van Kempen waltje@uwalt.nl.mugnet.org>, Bernd Eckenfels net-tools@lina.inka.de>.

Источник

How to Check and Clear the ARP Cache in Windows, Linux and Mac?

Invicti Web Application Security Scanner – the only solution that delivers automatic verification of vulnerabilities with Proof-Based Scanning™.

Misconfigured or expired ARP cache entries in the system might be one of the reasons for network connectivity problems.

Are you aware that clearing the ARP cache in your system may fix loading problems and connectivity errors?

This article will look at how to check and clear the ARP cache in the different operating systems.

What is ARP cache?

ARP stands for Address Resolution Protocol, which is responsible for discovering MAC addresses and mapping them to IP addresses in order to communicate successfully with other systems on the local network. This protocol works between the data link layer and network layer.

Instead of asking the router every time where the particular device is located and what its mac address is, our system would just connect using the previously resolved IP address.

When our systems find the MAC addresses for the particular IP address using ARP protocol, they will be stored in a table for future use. This table is called ARP cache. It contains a list of known IP addresses and their MAC addresses.

ARP request is a broadcast, and ARP reply is unicast.

When to clear the ARP cache ?

If the IP addresses of the network-linked devices change, ARP entries can get corrupted or expired, and new entries may not always overrule the database’s expired entries.

As a result, it may impact network performance and may cause loading or connectivity problems. In this case, you can simply clear the ARP cache to resolve the issue because clearing the ARP cache will cause all of your requests to go through the entire ARP process again. During this process, the new entries will be saved in the ARP table.

Some errors may occur during the rebuilding of the ARP cache table, so deleting the ARP cache all the time is not recommended. Instead, you can also reboot your router or system to resolve the connectivity problems.

How to clear the ARP cache?

We can easily clear the ARP cache in any operating system by using the command line. Let’s get started.

Windows

Step 1: Open a command prompt and run it as an administrator.

Step 2: To view the ARP cache table, just type the following command.

This command displays the IP addresses, and it’s associated mac addresses.

Step 3: Next, to delete the cache table, you can use netsh utility.

netsh interface IP delete arpcache

Step 4: If you want to delete any specific entry in the cache, not the whole table.

C:\WINDOWS\system32>arp -a Interface: 192.168.29.64 --- 0xd Internet Address Physical Address Type 192.168.29.1 a8-da-0c-e8-0e-e6 dynamic 224.0.0.22 01-00-5e-00-00-16 static 224.0.0.251 01-00-5e-00-00-fb static 224.0.0.252 01-00-5e-00-00-fc static Interface: 192.168.56.1 --- 0x14 Internet Address Physical Address Type 224.0.0.22 01-00-5e-00-00-16 static 224.0.0.251 01-00-5e-00-00-fb static 239.255.255.250 01-00-5e-7f-ff-fa static C:\WINDOWS\system32>netsh interface IP delete arpcache Ok.

You will get ‘OK’ as a response if you use the netsh utility to clear the cache table.

Linux

Step 1: Open a terminal and use the following IP utility command to clear the whole ARP table.

Step 2: If you want to delete the ARP record for a particular address, use arp utility.

Step 3: After deleting the entries, you can simply use the following command to view the ARP table in Linux.

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This command displays the whole arp table.

┌──(root💀kali)-[/home/geekflare] └─# arp -d 10.0.2.1 ┌──(root💀kali)-[/home/geekflare] └─# arp -n Address HWtype HWaddress Flags Mask Interface 10.0.2.1 (incomplete) 10.0.2.2 ether 01:00:5e:00:00:fc C eth0 10.0.2.3 ether a8:da:0c:e8:0e:e6 C eth0

Here, you can observe the cache entry for the specific address is cleared.

Mac

Step 2: To view the existing ARP entries.

Step 3: To delete the cache for a particular interface

sudo arp -d 192.168.29.1 ifscope en0

Step 4: To clear the whole cache table

$ sudo arp -a ? (192.168.29.1) at 01:00:5e:00:00:fc on en0 ifscope [ethernet] ? (192.168.2.13) at a8:da:0c:e8:0e:e6 on en0 ifscope [ethernet] ? (192.168.1.21) at 01:00:5e:00:0e:16 on en0 ifscope permanent [ethernet] $ sudo arp -a -d 192.168.29.1 (192.168.29.1) deleted 192.168.2.13 (192.168.2.13) deleted 192.168.1.21 (192.168.1.21) deleted

Conclusion

If you can’t ping a particular IP address in the same network even though they’re working correctly, it’s a sign that something is wrong. Your ARP cache table may need to be reconstructed again.

I hope you found this article helpful in learning how to clear the ARP cache in different operating systems.

Источник

Linux очистить arp таблицу

How to clear the ARP cache on Linux?

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