Linux, 2 machines using same IP

Posted on 2013-12-17
Medium Priority
Last Modified: 2013-12-18
I am using RHEL 6.4

I have gotten 15 client machines to work, but the 16th will not work

What I suspect is taht Another client or server is actually using th eIP of the machine, or some other strage IP issue

Sometimes I do an init 0 and another VM goes down, sometimes not

It can ping itself and other machines can ping it as well, but I see lots of strange behavior

How can I investigate >

Question by:Los Angeles1
  • 2
LVL 21

Accepted Solution

Mazdajai earned 500 total points
ID: 39725487
You can use nmap to swap the subnet. After you get the list of hostnames, you can use their mac address to determine where the duplicate machines are.

For example, VMware will have beginning mac of 00:50:56:00:00:00 - 00:50:56:3F:FF:FF. If they are physical machiness, use tracert to determine which switch it connects to.
LVL 81

Assisted Solution

arnold earned 1000 total points
ID: 39725569
Look in /var/log/messages there you should see an network event pointing to another system's MAC address as using the same IP.

If you have a managed switch look there.

Did you clone a VM such that you have two VMs with the same MAC address and you are using DHCP based IP reservation (mimic static IP behavior)?
With identical MAC addresses the DHCP receives a request from each and allocates sends both the same IP.
LVL 14

Assisted Solution

ThomasMcA2 earned 500 total points
ID: 39725728
Are all VMs pointing to the same DNS server? I have seen duplicated IPs when a 2nd DNS server was handing out IPs that conflicted with the primary server. If so, shut down the 2nd server, and fix the DNS settings to point to a single DNS server.
LVL 81

Assisted Solution

arnold earned 1000 total points
ID: 39725733
I too run into a similar issue where the typing gets away, DNS does not hand out IPs, it is a record keeping service. DHCP allocates IPs.

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