Static IP Post: 35989

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Special Forums IP Networking Static IP Post 35989 by Neo on Sunday 18th of May 2003 11:56:44 AM

05-18-2003

Administrator

Sorry, that is simply not true. We have a similar set up at home and use both DHCP and static addresses from the same address block. It works fine. Some PC get their addresses from the DHCP server (software in the Linksys router), others use assigned static IPs.

We don't do it, but the device can be configured to only allocate DHCP IPs from a small range of numbers. Unless you have a giant LAN that is using almost all the addresses, this is not a problem.

Since the poster indicated that they have a small LAN, simply assign a static IP outside of the 'normal' range of DHCP allocations.

And, if I'm not mistaken, ARP should make this moot in many DHCP servers; i.e. a good DHCP server should check its ARP cache before assiging an IP to check to see if it is in use on the segment.

For example, here is a quote from:

http://www.networkpenetration.com/dhcp_flaws.html

Quote:

Some DHCP servers issue ARP requests or ICMP pings to detect for IP addresses that may be reclaimed by the server. This is done as operating systems / interfaces do not release there assigned IP address when shutdown. Basic testing of the denial of service code successfully defeat the ARP method of reclaiming IP addresses (ICMP method was not tested) as the number and speed of requests for IP addresses was significantly higher than the number of ARP requests issued by the DHCP server (when running multiple copies of the source code in a script). The source code could be extended to sniff for ARP requests / ICMP ping requests and reply accordingly thus defeating the servers method of reclaiming addresses.

OBTW: if you are operating your own small private LAN, you don't need to be worried about the hypothetical DHCP vulnerability above.

Neo

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LEARN ABOUT CENTOS

switch_root

SWITCH_ROOT(8)						       System Administration						    SWITCH_ROOT(8)

NAME

       switch_root - switch to another filesystem as the root of the mount tree

SYNOPSIS

       switch_root [-hV]

       switch_root newroot init [arg...]

DESCRIPTION

       switch_root moves already mounted /proc, /dev and /sys to newroot and makes newroot the new root filesystem and starts init process.

       WARNING: switch_root removes recursively all files and directories on the current root filesystem.

OPTIONS

       -h, --help
	      show help and exit

       -V, --version
	      show version number and exit

RETURN VALUE

       switch_root returns 0 on success and 1 on failure.

NOTES

       switch_root  will  fail	to  function if newroot is not the root of a mount. If you want to switch root into a directory that does not meet
       this requirement then you can first use a bind-mounting trick to turn any directory into a mount point:

	      mount --bind $DIR $DIR

SEE ALSO

       mount(8), chroot(2), init(8), mkinitrd(8)

AUTHORS

       Peter Jones <pjones@redhat.com>
       Jeremy Katz <katzj@redhat.com>
       Karel Zak <kzak@redhat.com>

AVAILABILITY

       The switch_root command is part of the util-linux package and is available from ftp://ftp.kernel.org/pub/linux/utils/util-linux/.

util-linux							     June 2009							    SWITCH_ROOT(8)

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