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Promiscuous mode enabled??

Posted on 2004-09-25
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Last Modified: 2010-03-18
I face with this problem at my syslog...some one said it's dangerous...so i need an advice to fix this...

Sep 26 07:41:36 lynx kernel: tg3: eth0: Link is up at 100 Mbps, full duplex.
Sep 26 07:41:36 lynx kernel: tg3: eth0: Flow control is off for TX and off for RX.
Sep 26 07:42:02 lynx kernel: eth1: Promiscuous mode enabled.
Sep 26 07:42:02 lynx kernel: eth1: Promiscuous mode enabled.
Sep 26 07:42:02 lynx kernel: eth2: Promiscuous mode enabled.
Sep 26 07:42:02 lynx kernel: eth2: Promiscuous mode enabled.
Sep 26 07:42:02 lynx kernel: eth1: Promiscuous mode enabled.
Sep 26 07:42:02 lynx kernel: eth1: Promiscuous mode enabled.
Sep 26 07:42:02 lynx kernel: eth2: Promiscuous mode enabled.
Sep 26 07:42:02 lynx kernel: eth2: Promiscuous mode enabled.
Sep 26 07:42:12 lynx dhcpd: if IN A STAGVER.lynx.ath.cx rrset doesn't exist add 300 IN A STAGVER.lynx.ath.cx 192.168.1.2: timed out.
Sep 26 07:42:12 lynx dhcpd: DHCPREQUEST for 192.168.1.2 from 00:11:85:0d:b3:3e (STAGVER) via eth1
Sep 26 07:42:12 lynx dhcpd: DHCPACK on 192.168.1.2 to 00:11:85:0d:b3:3e (STAGVER) via eth1
Sep 26 07:47:13 lynx dhcpd: if IN A STAGVER.lynx.ath.cx rrset doesn't exist add 300 IN A STAGVER.lynx.ath.cx 192.168.1.2: timed out.
Sep 26 07:47:13 lynx dhcpd: DHCPREQUEST for 192.168.1.2 from 00:11:85:0d:b3:3e (STAGVER) via eth1
Sep 26 07:47:13 lynx dhcpd: DHCPACK on 192.168.1.2 to 00:11:85:0d:b3:3e (STAGVER) via eth1
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Question by:lilie795
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Expert Comment

by:jlevie
ID: 12152572
That's normal and necessary for a machine that's running a DHCP server, which yours obviously does.
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Author Comment

by:lilie795
ID: 12153637
you mean that just a log file for admin to see?
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by:fulp02
ID: 12155147
You can not spend your whole life reading log file find the stuff you need to know and grep it out.
so say you wanted to know anything going on with dhcp   grep *dhcp* syslogfile
Alittle off topic but it will save you loads of time in the end
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jlevie earned 180 total points
ID: 12155436
A Unix/Linux system will always log an interface being placed in promiscous mode. While there are legitimate reasons for that happening, it could be a rogue application like a password capture tool. Some of the legitimate reasons include:

A DHCP server
Authorized use of a sniffer (e.g. tcpdump, ethereal)
Any of the network Intrusion Detection Systems (e.g. snort)
Any of the network traffic analysis tools (e.g., ntop, iptraf, etc)

as the SysAdmin you'd know if any of those were in legitimate use on the system and thus know that the warning could be ignored if it only occurs when one of those was started. Seeing that at any other time would be cause for alarm and investigation.
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