One of the client comptuers(pc-7) has a printer connected with usb and is shared. The computer has dynamic IP. All of a sudden users couldn't print to that shared printer from other comptuers. Tried few things and eventually logged on to SBS03 and found two comptuers have same IP of 192.168.0.3, pc-5 and pc-7. Then we manually set IP of pc-5 to 192.168.0.113. but when we ping pc-5 it still links to 192.168.0.3, then we change ip of pc-7 to 192.168.0.114. and when ping pc-7 it still links to 192.168.0.3 too. Deleted both ip address from dhcp server as well, restarted SBS, and both comptuer. For now we have disconnected PC-5 and manually set PC-7's ip address to 192.168.0.3 other wise no matter what it doesn't print from other computer. Is there any way to clear it? by the way PC-5 wasn't used for months, would it be pc-5 had 192.168.0.3 ip already and when connected two comptuers got same ip address.
> One of the client comptuers(pc-7) has a printer connected with usb and is > shared. The computer has dynamic IP. All of a sudden users couldn't print > to > that shared printer from other comptuers. Tried few things and eventually > logged on to SBS03 and found two comptuers have same IP of 192.168.0.3, > pc-5 > and pc-7. Then we manually set IP of pc-5 to 192.168.0.113. but when we > ping > pc-5 it still links to 192.168.0.3, then we change ip of pc-7 to > 192.168.0.114. and when ping pc-7 it still links to 192.168.0.3 too. > Deleted > both ip address from dhcp server as well, restarted SBS, and both > comptuer. > For now we have disconnected PC-5 and manually set PC-7's ip address to > 192.168.0.3 other wise no matter what it doesn't print from other > computer. > Is there any way to clear it? by the way PC-5 wasn't used for months, > would > it be pc-5 had 192.168.0.3 ip already and when connected two comptuers got > same ip address.
First, you have to understand that DHCP just hands out addresses. (well, technically it can do a lot more, but for the merits of this conversation...)
It does NOT control how IP traffic gets from point A to point B at any time.
Let's use a valet service as an example. When going to a restaurant (a fancy one that invests in silly technology like my example...bear with me), the valet types in your license-plate, parks your car, and gives you a ticket. Your ticket now has the license-plate and the parking space printed on it.
So one night, I go to the restaurant and park my car. I get a ticket that says pc-5 is parked in 192.168.0.3. In the DHCP world, this is a lease. Two weeks later, you go to the same restaurant and you get a ticket. pc-7 is parked in 192.168.0.3. Two tickets, same IP. But they aren't in conflict because the two cars were not parked there *at the same time.* The parking space got reused because it was vacant. Again, in the DHCP world, leases expire.
Now to the important stuff. When you ping a machine, the first thing the OS does is tries to resolve the machine name to an IP address. There are several ways to do this: DNS, WINS, neighbor discovery, etc. But SBS when setup properly will use DNS first. So when you manually set the IP address if pc-5 to another address...192.168.0.113 in your example, you didn't update the DNS entry on the DNS server. So a ping still does the DNS lookup, DNS still has a record (you didn't delete that) and pings the machine *REGARDLESS OF NAME* at 192.168.0.3. Same goes for pc-7. You are manually changing the IP address, but not changing the DNS record.
But the real rub here is that DHCP will update DNS records for you. By changing the IP address manually, you were not letting DHCP do what it does best. It hands out an address and then updates DNS. If had just deleted the DHCP leases from the DHCP server and then rebooted both clients (not the server!) they'd have re-requested IP addresses and DHCP will *not* issue the same IP to multiple machines at the same time. One would've gotten 192.168.0.3 and one would've gotten a new address.
So to answer the two questions you ended with (in order), yes, it sounds like pc-5 had 192.168.0.3 at one time. And no, the two machines would not have gotten the same IP address.
As an additional note, with any computer that has a shared resource, it is best to make sure they always get the same IP address. You can do this with DHCP by setting up a DHCP reservation. That way you won't ever have the DHCP server handing that address out to another machine, and even better, you get the benefit of the DHCP server updating the DNS server. Unless you know *exactly* what you are doing, *!!!NEVER!!!* manually assign IP addresses. It only causes more headaches and, as you've already discovered, causes troubleshooting pains.
-Cliff
"tim09" <ti...@discussions.microsoft.com> wrote in message
> One of the client comptuers(pc-7) has a printer connected with usb and is > shared. The computer has dynamic IP. All of a sudden users couldn't print > to > that shared printer from other comptuers. Tried few things and eventually > logged on to SBS03 and found two comptuers have same IP of 192.168.0.3, > pc-5 > and pc-7. Then we manually set IP of pc-5 to 192.168.0.113. but when we > ping > pc-5 it still links to 192.168.0.3, then we change ip of pc-7 to > 192.168.0.114. and when ping pc-7 it still links to 192.168.0.3 too. > Deleted > both ip address from dhcp server as well, restarted SBS, and both > comptuer. > For now we have disconnected PC-5 and manually set PC-7's ip address to > 192.168.0.3 other wise no matter what it doesn't print from other > computer. > Is there any way to clear it? by the way PC-5 wasn't used for months, > would > it be pc-5 had 192.168.0.3 ip already and when connected two comptuers got > same ip address.
> First, you have to understand that DHCP just hands out addresses. (well, > technically it can do a lot more, but for the merits of this > conversation...)
> It does NOT control how IP traffic gets from point A to point B at any > time.
> Let's use a valet service as an example. When going to a restaurant (a > fancy one that invests in silly technology like my example...bear with > me), the valet types in your license-plate, parks your car, and gives you > a ticket. Your ticket now has the license-plate and the parking space > printed on it.
> So one night, I go to the restaurant and park my car. I get a ticket that > says pc-5 is parked in 192.168.0.3. In the DHCP world, this is a lease. > Two weeks later, you go to the same restaurant and you get a ticket. pc-7 > is parked in 192.168.0.3. Two tickets, same IP. But they aren't in > conflict because the two cars were not parked there *at the same time.* > The parking space got reused because it was vacant. Again, in the DHCP > world, leases expire.
> Now to the important stuff. When you ping a machine, the first thing the > OS does is tries to resolve the machine name to an IP address. There are > several ways to do this: DNS, WINS, neighbor discovery, etc. But SBS when > setup properly will use DNS first. So when you manually set the IP > address if pc-5 to another address...192.168.0.113 in your example, you > didn't update the DNS entry on the DNS server. So a ping still does the > DNS lookup, DNS still has a record (you didn't delete that) and pings the > machine *REGARDLESS OF NAME* at 192.168.0.3. Same goes for pc-7. You are > manually changing the IP address, but not changing the DNS record.
> But the real rub here is that DHCP will update DNS records for you. By > changing the IP address manually, you were not letting DHCP do what it > does best. It hands out an address and then updates DNS. If had just > deleted the DHCP leases from the DHCP server and then rebooted both > clients (not the server!) they'd have re-requested IP addresses and DHCP > will *not* issue the same IP to multiple machines at the same time. One > would've gotten 192.168.0.3 and one would've gotten a new address.
> So to answer the two questions you ended with (in order), yes, it sounds > like pc-5 had 192.168.0.3 at one time. And no, the two machines would not > have gotten the same IP address.
> As an additional note, with any computer that has a shared resource, it is > best to make sure they always get the same IP address. You can do this > with DHCP by setting up a DHCP reservation. That way you won't ever have > the DHCP server handing that address out to another machine, and even > better, you get the benefit of the DHCP server updating the DNS server. > Unless you know *exactly* what you are doing, *!!!NEVER!!!* manually > assign IP addresses. It only causes more headaches and, as you've already > discovered, causes troubleshooting pains.
> -Cliff
I just want to add:
By default, a Windows 2000 and newer statically configured machines will register their A record (hostname) and PTR (reverse entry) into DNS.
If set to DHCP, a Windows 2000 or newer machine will request DHCP to allow the machine itself to register its own A record, but DHCP will register its PTR (reverse entry) record.
However one problem with that, if the client shuts down, and later on when it comes back up past the lease time, it may get a different IP address. What happens here is a duplicate A record gets created with the new IP because the client will not update itself due to the current record in DNS is beyond the lease period. This happens even though DHCP registered the record. This is because DHCP doesn't own the record, the client does, even though DHCP registered it.
The way to get around this is you can configure DHCP to update the record for the client, no matter what the client asks. What we want to do to keep DNS clean without additional records with the same name but different IP address in DNS. To do this, DHCP must own the record, not the client, so it can keep it up to date, no matter if the record is being the lease or not. Therefore, as long as DHCP owns the record, it will update the record in DNS when and if DHCP gives the machine a new IP. Otherwise you'll see multiples A and PTR records of the same in DNS whether scavenging is enabled or not.
I also suggest to configure DHCP to register all DHCP clients, whether the client supports Dynamic Updates or not. This way all DHCP clients get registered and DHCP owns the record. I suggest to enable DNS scavenging to remove stale records, which will keep the zone clean.
For Tim09:
To force DHCP to own records, simply create a user account, (a non-domain admin account), provide a secure password, go into the DHCP console, righ-click DHCP server name, properties, Click on the last tab, click on Credentials button, supply the user account name and password.
To enable scavenging on the zone, please read my blog in the following link:
Two paths to the same end. I prefer letting the client register itself...less to change, easier to troubleshoot, and doesn't require adding credentials to the DHCP server...fewer credentials floating around is better from a security standpoint in my opinion.
Instead I tweak stale record scavenging based on the environment and how long any machine is expected to be out of contact. This is, of course, very organization specific and depends on laptops, how long they may be off-site, and other factors. But it accomplishes the same ultimate goal of removing old A records.
> "Cliff Galiher" <cgali...@gmail.com> wrote in message > news:%23KPbSmPYKHA.1236@TK2MSFTNGP05.phx.gbl... >> First, you have to understand that DHCP just hands out addresses. (well, >> technically it can do a lot more, but for the merits of this >> conversation...)
>> It does NOT control how IP traffic gets from point A to point B at any >> time.
>> Let's use a valet service as an example. When going to a restaurant (a >> fancy one that invests in silly technology like my example...bear with >> me), the valet types in your license-plate, parks your car, and gives you >> a ticket. Your ticket now has the license-plate and the parking space >> printed on it.
>> So one night, I go to the restaurant and park my car. I get a ticket >> that says pc-5 is parked in 192.168.0.3. In the DHCP world, this is a >> lease. Two weeks later, you go to the same restaurant and you get a >> ticket. pc-7 is parked in 192.168.0.3. Two tickets, same IP. But they >> aren't in conflict because the two cars were not parked there *at the >> same time.* The parking space got reused because it was vacant. Again, >> in the DHCP world, leases expire.
>> Now to the important stuff. When you ping a machine, the first thing the >> OS does is tries to resolve the machine name to an IP address. There are >> several ways to do this: DNS, WINS, neighbor discovery, etc. But SBS >> when setup properly will use DNS first. So when you manually set the IP >> address if pc-5 to another address...192.168.0.113 in your example, you >> didn't update the DNS entry on the DNS server. So a ping still does the >> DNS lookup, DNS still has a record (you didn't delete that) and pings the >> machine *REGARDLESS OF NAME* at 192.168.0.3. Same goes for pc-7. You >> are manually changing the IP address, but not changing the DNS record.
>> But the real rub here is that DHCP will update DNS records for you. By >> changing the IP address manually, you were not letting DHCP do what it >> does best. It hands out an address and then updates DNS. If had just >> deleted the DHCP leases from the DHCP server and then rebooted both >> clients (not the server!) they'd have re-requested IP addresses and DHCP >> will *not* issue the same IP to multiple machines at the same time. One >> would've gotten 192.168.0.3 and one would've gotten a new address.
>> So to answer the two questions you ended with (in order), yes, it sounds >> like pc-5 had 192.168.0.3 at one time. And no, the two machines would >> not have gotten the same IP address.
>> As an additional note, with any computer that has a shared resource, it >> is best to make sure they always get the same IP address. You can do >> this with DHCP by setting up a DHCP reservation. That way you won't ever >> have the DHCP server handing that address out to another machine, and >> even better, you get the benefit of the DHCP server updating the DNS >> server. Unless you know *exactly* what you are doing, *!!!NEVER!!!* >> manually assign IP addresses. It only causes more headaches and, as >> you've already discovered, causes troubleshooting pains.
>> -Cliff
> I just want to add:
> By default, a Windows 2000 and newer statically configured machines will > register their A record (hostname) and PTR (reverse entry) into DNS.
> If set to DHCP, a Windows 2000 or newer machine will request DHCP to allow > the machine itself to register its own A record, but DHCP will register > its PTR (reverse entry) record.
> However one problem with that, if the client shuts down, and later on when > it comes back up past the lease time, it may get a different IP address. > What happens here is a duplicate A record gets created with the new IP > because the client will not update itself due to the current record in DNS > is beyond the lease period. This happens even though DHCP registered the > record. This is because DHCP doesn't own the record, the client does, even > though DHCP registered it.
> The way to get around this is you can configure DHCP to update the record > for the client, no matter what the client asks. What we want to do to keep > DNS clean without additional records with the same name but different IP > address in DNS. To do this, DHCP must own the record, not the client, so > it can keep it up to date, no matter if the record is being the lease or > not. Therefore, as long as DHCP owns the record, it will update the record > in DNS when and if DHCP gives the machine a new IP. Otherwise you'll see > multiples A and PTR records of the same in DNS whether scavenging is > enabled or not.
> I also suggest to configure DHCP to register all DHCP clients, whether the > client supports Dynamic Updates or not. This way all DHCP clients get > registered and DHCP owns the record. I suggest to enable DNS scavenging to > remove stale records, which will keep the zone clean.
> For Tim09:
> To force DHCP to own records, simply create a user account, (a non-domain > admin account), provide a secure password, go into the DHCP console, > righ-click DHCP server name, properties, Click on the last tab, click on > Credentials button, supply the user account name and password.
> To enable scavenging on the zone, please read my blog in the following > link:
> This posting is provided "AS-IS" with no warranties or guarantees and > confers no rights.
> Please reply back to the newsgroup or forum for collaboration benefit > among responding engineers, and to help others benefit from your > resolution.
> Two paths to the same end. I prefer letting the client register > itself...less to change, easier to troubleshoot, and doesn't require > adding credentials to the DHCP server...fewer credentials floating around > is better from a security standpoint in my opinion.
> Instead I tweak stale record scavenging based on the environment and how > long any machine is expected to be out of contact. This is, of course, > very organization specific and depends on laptops, how long they may be > off-site, and other factors. But it accomplishes the same ultimate goal > of removing old A records.
> -Cliff
That is one way to do it, it's just that it won't update an existing record, unfortunately.
Tim, there are a bunch of folks posting in the nntp interface but it's not being replicated back to the web forum. Sorry about that. -- http://www.sbslinks.com/really.htm
"tim09" wrote: > One of the client comptuers(pc-7) has a printer connected with usb and is > shared. The computer has dynamic IP. All of a sudden users couldn't print to > that shared printer from other comptuers. Tried few things and eventually > logged on to SBS03 and found two comptuers have same IP of 192.168.0.3, pc-5 > and pc-7. Then we manually set IP of pc-5 to 192.168.0.113. but when we ping > pc-5 it still links to 192.168.0.3, then we change ip of pc-7 to > 192.168.0.114. and when ping pc-7 it still links to 192.168.0.3 too. Deleted > both ip address from dhcp server as well, restarted SBS, and both comptuer. > For now we have disconnected PC-5 and manually set PC-7's ip address to > 192.168.0.3 other wise no matter what it doesn't print from other computer. > Is there any way to clear it? by the way PC-5 wasn't used for months, would > it be pc-5 had 192.168.0.3 ip already and when connected two comptuers got > same ip address.
on PC 7 go to dos prompt and run ipconfig /release ipconfig /flushdns ipconfig / renew
will pick up new address could still be same as before. on server go to DHCP and reserve it Printing to a shared printer has nothing to do with the ip but with Netbios
Now swtich on PC5 and do the same except no need to reserve the ip
If still problem on server goto WINS restart the service and delete any tombstoned records
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