One machine responds with IP address of another..

I am having machine A hostname responding with IP of B. Same user.  And vice-versa.  In DHCP is other way around.
Tried to sudo dhclient, etc.  Restart, nothing helps.
Both ubuntu machines.
What troubleshooting steps take here?
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Tiras25Asked:
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timgreen7077Exchange EngineerCommented:
if there is a DNS server in the environment, make sure that the 'A' have the correct computer names and IP addresses.
timgreen7077Exchange EngineerCommented:
I don't know anything about Linux machines but in Windows you could run ipconfig /flushdns to make sure the local computer DNS cache is also cleared of older DNS entries.
MaheshArchitectCommented:
which DHCP you are using?
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nappy_dThere are a 1000 ways to skin the technology cat.Commented:
I recall you recently posted a topic when you migrated to AD and DNS.

If these computers are using DHCP you need to make sure you have these computers joined to AD to be able to dynamically update DNS or if the computers are not part of AD, you may have to turn off authenticated DNS updates for AD to allow non AD machines to update DNS
Tiras25Author Commented:
yes did that.  the client is ubuntu os.
nociSoftware EngineerCommented:
Or put the hostnames  as static in DNS (do prevent enpunging / cleaning by DNS server)  and also assign reserved leases to those systems, or even set them up as static address systems.
arnoldCommented:
login into each system and run ifconfig -a
this will list the IPs on the system.
hostname will return the hostname of the system.

As others pointed out the DNS records were mixed up, not sure what you reference on the DHCP side, the likely issue is data entry error if I understand the situation.

i.e.
you believe the configuration is:
a.b.c.d is hostname1
e.f.g.h is hostname2

ping hostname1 and you get replies from e.f.g.h
ping hostname 2 and you get replies from a.b.c.d

What does nslookup a.b.c.d and e.f.g.h return, do these match the nslookup for hostname1 and hostname2

Presumably you may have DHCP register hosts in DNS?

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nociSoftware EngineerCommented:
@arnold: a previous question of asker was about migrating a working DHCP/DNS (Linux based) to AD...
For AD one needs to be a domain member to update AD / DNS part  (Or allow everyone to update the DNS).
maybe recent Windows DHCP can update the central DNS, i was told in the past that that could not be done...
Tiras25Author Commented:
nslookup shows unknown.  Can't find.  Non-existed domain.  Weird that all existend machines migrated and picked by new DHCP with bind DNS.  The new ones having issues with it..
nappy_dThere are a 1000 ways to skin the technology cat.Commented:
Do you have DNS unsecured or secured with your AD DNS?

Here is how to check if you are using Secured or unsecured DNS(By default it is set to secured).  Can you verify?

  1. Open DNS
  2. Expand and select your FQDN
  3. Right-click and select properties
  4. On the general tab, is it set to secured or unsecured for dynamic updates?

Secured or unsecured DNS
Tiras25Author Commented:
secure only
nappy_dThere are a 1000 ways to skin the technology cat.Commented:
Try setting it to unsecured or you will need to have your Linux machines joined to AD to be able to dynamically update their DNS records.

If you cannot do that then I suggest you configure static entries for your non-AD joined machines.

CLICK HERE for more info
arnoldCommented:
@noci, thanks was unclear whether this issue related to the DHCP migration so was addressing as an unrelated seemingly mismatch in registration/hosts. either if IP reservation is the issue, the wrong MAC address was tied to the wrong IP.
MAC address of hostname1 has a reservation for the IP of hostname2..

DHCP since 2003 can be configured to register both the forward and the reverse versus relying on the client (system getting the IP) to register the records in DNS. The default functionality as earlier comments point to, windows DHCP will be authorized to register records in the DNS zone (forward) the reverse zones would need to be manually added. I always add the 10 10.in-addr.arpa to quell any attempt to lookup 10.x.y.z,172.16-31.0 and 192.168. publicly going to the blackhole DNS server that do not exist and need the timeout 10-30 seconds before the local DNS server gives up and returns the nohost .....


The setup on DHCP is often to designate the registration in DNS for the clients to whom it issues an IP as well as to delete the record when the lease expires. IP released.

The windows DNS would need to have the reverse zones added as authoritative as illustrated in the above comment by nappy_d but for the reverse zone c.b.a.in-addr.arpa for to which DHCP will send the name of the system to which it gave ip a.b.c.d in addition to the registration it makes to the forward zone
i.e. one record is somehost.somedomain.com with IP a.b.c.d
one record for reverse a.b.c.d in c.b.a.in-addr.arpa with PTR somehost.somedomain.com
both records will be temporary based on the lease duration....../TTL.

Have had situation when data entry, i.e. have a list of hosts and IPs, and during the DNS addition, transpose one for another.....

to untangle, login to the host you want, by name or IP, and see if it matches what was expected.
If the issue is merely in DNS, updating the DNS records is fairly straight forward.
but if this is a reservation typo,
manually the reservations need to be deleted, if memory serves, it will not let you make changes to the reservation record and it will not let you add the same mac address with a new IP reservation.

using script vbscript, powershell, or netsh it might be possible .......
 netsh dhcp server ...

unwinding/untangling what the issue/situation is would be first, then the remedy should be clear.
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