Bug 138758 - ARP setting from command line accept but not work.
ARP setting from command line accept but not work.
Product: Fedora
Classification: Fedora
Component: net-tools (Show other bugs)
i686 Linux
medium Severity medium
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Assigned To: Radek Vokal
Ben Levenson
: Security
Depends On:
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Reported: 2004-11-10 19:22 EST by Jevgeni Maksimov
Modified: 2007-11-30 17:10 EST (History)
1 user (show)

See Also:
Fixed In Version:
Doc Type: Bug Fix
Doc Text:
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Clone Of:
Last Closed: 2004-11-12 02:51:01 EST
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oVirt Team: ---
RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: ---

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Description Jevgeni Maksimov 2004-11-10 19:22:29 EST
Description of problem:
On RedHat 9.0 I use next command for link IP to MAC:

arp -v -n -a -s 00:10:4A:06:D1:7A
Verbose mode answer:

If user changed IP address Internet not worked
Return back IP and Internet start worked okey.

On second workstation where I install Fedora Core 3 Final from 

But on this machine I use external IP addresses for my network and 
trying to use same command but only for external IP's:
arp -v -n -a -s 00:40:4A:06:D1:7A
Verbose mode answer:

If user change IP on his PC, it is staying to get Internet.

What se problem, maybe bug?
If not, what I do incorrectly and how use this command correctly?

What different between RH 9.0 Kernel 2.4.20-31.9 and FC3 Kernel 2.6.9-
1.667 in this command?

Version-Release number of selected component (if applicable):

How reproducible:
Every time.

Steps to Reproduce:
Actual results:

Expected results:
No effect.

Additional info:
Comment 1 Radek Vokal 2004-11-11 07:50:36 EST
Hi, well firstly I'm not completely sure what are you trying to
achieve? You can't set local IP adress with ARP and the correct way to
do this is using ifup for the device. This is propably not a bug. 
Comment 2 Jevgeni Maksimov 2004-11-11 15:29:09 EST
On machine where FC3 configured as GATEWAY for users in my network 
which used non local IP(192.168.*.*) but external IP's.
And I trying to control to block not authorised IP to access to 
Internet. I use for it for allowed IP's
arp -v -n -a -s 00:40:4A:06:41:7A
arp -v -n -a -s 00:80:EA:08:11:EE
arp -v -n -a -s 00:40:6A:0A:A1:EA

For other IP's which not used but present in my network I use secret 
MAC combination, for example:
arp -v -n -a -s AA:BB:AA:BB:BB:BB
arp -v -n -a -s AA:BB:AA:BB:BB:BB
arp -v -n -a -s AA:BB:AA:BB:BB:BB

And this accepted but not work!!!

If user write to itself, IP which in ARP table with MAC 
AA:BB:AA:BB:BB:BB, but his network card have realy MAC 
This user stay to use Internet.

Bug in iputils?
Comment 3 Radek Vokal 2004-11-12 02:51:01 EST
Well I think you're trying a really strange way to do this. I would suppose to
use iptables (check man page for mac and mac_source) which will do this job for
you 100times better. I'm not completely sure whether this is a bug or not, but
IMHO arp works correctly and it's only about the way how kernel is using arp
cache and arp table. While arp reponds with arp: SIOCSARP() the mac adress is
for sure set in the table but propably kernel rewrites it back when receives
certain packets from the other machine. 

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