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Dual NICs internal ping responds to same address

Posted on 2004-08-19
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Last Modified: 2012-06-27
I have two nics in a windows 2000 advanced server. The server itself is a Dell 2650.

Server1
NIC1 172.21.35.60 DNS entry is server1
NIC2 172.21.35.61 DNS entry is Server1a

from a command prompt at Server1 console

if I do a ping for Server1 i get a response to IP address 172.21.35.61
if I do a ping for Server1a i get a response to IP address 172.21.35.61

If I disable NIC2 and do a ping I get a response to IP address 172.21.35.60.

Does this make sense to anyone? I don't understand why this is happening internally on the server.
If I do a ping externally the NICs respond as expected. This is really wierd.
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Question by:bmwiest
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by:illushinz
illushinz earned 60 total points
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Sounds like a combination of DNS and ARP.  Is Server1 the DNS server or is DNS somewhere else?

Try:
ipconfig /flushdns
 then
arp -d
 then retry the pings and see if the results are different.  That will at least help you to start determining where Server1 is getting the information from.
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by:dneufeld
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yes it makes sense, the server has one name but many adresses. Check you DNS, you might have two entires for each server1 and server1a. Typically this is for load balancing. If you want to seperate your traffic between the NICs, I would suggest to use a DNS alias.

for instance website1 should go to server1 IP, so you make an alias for website1 to point to the .60 address, not the server1 name, then website1A should get an alias to point to .61

this way you have two websites on one server but each nic will handle traffic for it's assigned web site. Traffic destined for the server will go to which ever nic is most avaiable.

hope this helps
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PennGwyn earned 70 total points
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Two NICs onto the same network is not really a supported configuration, and weird (non-obvious) things may happen as you've discovered.

PROBABLY what you actually want is "teaming" of the NICs, to double the bandwidth to this network available to the server.  That requires specific support in both the driver (the NICs must generally be of the same make/model for this to work) AND in the network switch they connect to.

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by:ErikPhilips
ErikPhilips earned 60 total points
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Also check if you have WINS enabled.  I believe machines will use WINS/Broacast via Netbios before using DNS.  Windows machines register themselves on the network with netbios (with or w/o wins) with whatever "computer name" they have.
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by:bmwiest
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I found that the server was working as was expected. The issue was binding. If you go into Network and Dial Up Connection window and click on advanced then advanced settings I had my NIC's in the wrong binding order. Once I put NIC1 1st int he order that fixed it.
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