Two NICs in one machine and same LAN?

  • Thread starter Thread starter RQ
  • Start date Start date
R

RQ

Hi,
If I setup two NICs using 10.1.1.1/24 and 10.1.1.2/24 addresses in one
machine, what could be happen? Can DNS handle this? Will it work in the
network?
Thanks,
Roger
 
Why? This is usually not a good idea and does nothing for your network
except cause confusion. What are you trying to accomplish with these 2 nics?
 
I know this is not a good idea, but our database guy wants to set second NIC
up on secondary database server using primary server's IP when the primary
goes down and still keep secondary server's first NIC IP active.
I don't know how to prove this is not a good idea. Please help.
Roger
 
In
RQ said:
I know this is not a good idea, but our database guy
wants to set second NIC up on secondary database server
using primary server's IP when the primary goes down and
still keep secondary server's first NIC IP active.
I don't know how to prove this is not a good idea. Please
help.
Click to expand...

It is never a good idea to put two NICs on the same machine on the same
subnet unless, they are teamed.
 
In
RQ said:
Would you please provide a answer why it's not a good
idea?
Click to expand...
Because they are different networks, and should be addressed acordingly.
Lets say that there is a machine with IP 10.1.1.3, which network provides
the way to that machine?
If one is 10.1.1.x and the other is also 10.1.1.x the machine won't know
which way to go to get to a machine that is on one or the other networks.
One should be 10.1.1.x and the other could be 10.1.0.x.
If both NICs are on the same subnet, they should be teamed and would only
have one IP address for both NICs. If you have two NICs on the same machine
with different IP addresses looking at each other (not teamed) only one will
get used at a time. Plus, if you have NetBIOS enabled, one of the NICs if
not both will be disabled due to a NetBIOS name conflict. It is like having
to machines on the same Network with the same NetBIOS name.

Suppose a query is sent to DNS for this machine and DNS gives the 10.1.1.1
address but that address is not on the subnet that has that address?
Ther is no way for DNS to know which address to give, it will just use round
robin. If they are on different subnets, DNS will use Netmask ordering to
give the correct record. (based on 10.1.1.x or 10.1.0.x)
 
Thanks Kevin, it helps.


Kevin D. Goodknecht Sr. said:
In
Because they are different networks, and should be addressed acordingly.
Lets say that there is a machine with IP 10.1.1.3, which network provides
the way to that machine?
If one is 10.1.1.x and the other is also 10.1.1.x the machine won't know
which way to go to get to a machine that is on one or the other networks.
One should be 10.1.1.x and the other could be 10.1.0.x.
If both NICs are on the same subnet, they should be teamed and would only
have one IP address for both NICs. If you have two NICs on the same machine
with different IP addresses looking at each other (not teamed) only one will
get used at a time. Plus, if you have NetBIOS enabled, one of the NICs if
not both will be disabled due to a NetBIOS name conflict. It is like having
to machines on the same Network with the same NetBIOS name.

Suppose a query is sent to DNS for this machine and DNS gives the 10.1.1.1
address but that address is not on the subnet that has that address?
Ther is no way for DNS to know which address to give, it will just use round
robin. If they are on different subnets, DNS will use Netmask ordering to
give the correct record. (based on 10.1.1.x or 10.1.0.x)
Click to expand...
 
If redundancy is what your looking for maybe you should investigate clustering the SQL servers.

Ian Bagnald
MCSE:Security Windows 2000
MCSA:Security Windows 2000
COMPTIA A+
 
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