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Author Topic: ip address  (Read 34183 times)

fordem

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Re: ip address
« Reply #45 on: June 01, 2010, 01:15:21 PM »

Here is the guy who made this job a little bit easier by creating simple netbios scanning app:

http://scottiestech.info/2009/02/14/how-to-determine-the-master-browser-in-a-windows-workgroup/

BTW, when you said you could ping NAS does it mean you could ping it by its name?

It you still have HOSTS file configured, you may also try to change NAS name there a little bit (make it DNS-323a for example) and try to play from there, to make sure NetBIOS and DNS names are different.

When you request NAS by entering \\dns-323\  somewhere in network neighborhood your machine AFAIK sends netbios broadcast asking "who the heck is DNS-323?" and expects to receive IP from NAS.
If you go to network neighborhood and try to browse list of workgroups, you get it from master browser, which should have DNS name-IP mapping obtained from NAS when it came online and sent broadcast "here I am, DNS-323, my IP is X.X.X.X".


Check you network with that tool (link) and see who is master browser on your network, workgroups etc. It is very strange that no computers see NAS netbios name. It means either it failed to send udp notification  broadcast on startup or it did not reach any destination. Don't you use any "non-standard" name for NAS by any chance (longer that 15 symbols, special characters etc.)? Is link and port to NAS reliable?

Seems to me there maybe some confusion here between the workings of ethernet, netbios and tcp/ip - netbios functions in the absence of tcp/ip so the concept of a netbios broadcast looking for a reply containing an ip address seems more than a little incorrect.

I don't know if you're aware of this, but not only are ip addresses NOT required for local area network communications, they are NOT used, even when tcp/ip is the only network protocol in play.  In local area network communications it is the MAC addresses that are used to identify the source & destination hosts rather than the ip addresses.
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gunrunnerjohn

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Re: ip address
« Reply #46 on: June 01, 2010, 01:25:34 PM »

Pretty hard to have a connection when you don't have an IP address on your local network. ;)
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rector

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Re: ip address
« Reply #47 on: June 01, 2010, 04:12:51 PM »

Here is the guy who made this job a little bit easier by creating simple netbios scanning app:

http://scottiestech.info/2009/02/14/how-to-determine-the-master-browser-in-a-windows-workgroup/

BTW, when you said you could ping NAS does it mean you could ping it by its name?

It you still have HOSTS file configured, you may also try to change NAS name there a little bit (make it DNS-323a for example) and try to play from there, to make sure NetBIOS and DNS names are different.

When you request NAS by entering \\dns-323\  somewhere in network neighborhood your machine AFAIK sends netbios broadcast asking "who the heck is DNS-323?" and expects to receive IP from NAS.
If you go to network neighborhood and try to browse list of workgroups, you get it from master browser, which should have DNS name-IP mapping obtained from NAS when it came online and sent broadcast "here I am, DNS-323, my IP is X.X.X.X".

Check you network with that tool (link) and see who is master browser on your network, workgroups etc. It is very strange that no computers see NAS netbios name. It means either it failed to send udp notification  broadcast on startup or it did not reach any destination. Don't you use any "non-standard" name for NAS by any chance (longer that 15 symbols, special characters etc.)? Is link and port to NAS reliable?

Hi, Thanks for the response
When I pinged the NAS, that is when it had been rebooted and not available to the network, I pinged it by IP and a response of the 4 packets was error free.

I used btstat -a pcname and the NAS is shown as the master browser

No non standard name for the NAS. I purposly called it DNS-323 so it was easy to remember for future.
No I havent noticed any strange numbers in reference to the NAS

Dont know if this will help, but if I swith off all pcs on the network, after running config on the NAS, that is the NAS is available to the network, on rebooting any pc on the network the NAS is available immediately. The problem is only when the Nas is turned off, and not a network pc.  


Last night I tried this
Disconnect one of my networked (wired) xp pcs from the network
Connect the NAS to the xp pc direct
Reset the xp Ip address from auto to one different to the NAS
Set the subnet to the same as the NAS
Set the default path to the IP of the NAS

Set the preferred DNS the same as the NAS

No changes were made to the NAS
I can now turn my NAS off, and when rebooted its available automatically, it works without entering config.  

Thanks
« Last Edit: June 01, 2010, 07:00:06 PM by rector »
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gunrunnerjohn

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Re: ip address
« Reply #48 on: June 01, 2010, 06:02:14 PM »

Correct, you have it as your master browser and when you turn it off, the network is confused.  I disabled the master browser capability of my two D-Link NAS boxes.
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OlegMZ

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Re: ip address
« Reply #49 on: June 01, 2010, 07:30:13 PM »

Seems to me there maybe some confusion here between the workings of ethernet, netbios and tcp/ip - netbios functions in the absence of tcp/ip so the concept of a netbios broadcast looking for a reply containing an ip address seems more than a little incorrect.

Really? First of all I tried to simplify my explanation and make it as short as possible in order not to overwhelm a reader with unnecessary details. But I still do not see where is the confusion?
NetBIOS works on 5th (session) layer of OSI model, while UDP protocol is on Layer 4 (transport) layer and IP is on Layer 3 (network) layer.

Here is the full model of communications according to OSI:

Layer 7. Application. Applications like Browser work on this layer using, SMB or HTTP protocols
Layer 6. Presentation. Determines formatting of data for Layer 7 (ASCII, JPEG etc.)
Layer 5. Session. Provides protocol of signalling and data exchenge between applications - NetBIOS for example with its set of queries and responses.
Layer 4. Transport. Provides Transport protocol for delivering data obtained from layers above. It may be UDP, TCP, ESP. AH etc for TCP/IP stack, may be NetBEUI, may be SPX for IPX/SPX stack etc. Layers above do not care much about type of protocol used at this level.
Layer 3. Network. Provides network protocol which is responsible for delivering data formed at the above level. For TCP/IP stack it is IP protocol, for IPX/SPX it is IPX, for NteBEUI ... it is NetBEUI itself as it is very simple and covers both levels at the same time.  There again may be other protocols as well. Layers 5 -7 do not care which ones. Routers are called Layer 3 devices because they operate at this layer (and below.)
Level 2. Data link. It defines protocol of data transmission between 2 nodes. This may be Ethernet, Token Ring, PPP, Serial, ATM, Frame Relay etc. Switches are L2 devices because they operate at this leayer and below. They have no idea about IP, IPX, Apple Talk, Powerline protocols etc. They know about MAC addresses only. BTW MAC address is used only by some of L2 protocols. Serial cards do not have them for example. This layer does not care about Layer 1.
Level 1. Physical. This layer provides physical media for layer above - twisted copper pair, electrical wiring (for powerline adapters), optical fiber, Wi-Fi, CDMA, 3G, GPRS, GSM,  etc.

When computer needs to transfer data to another host, data passes through all the layers top to bottom, and then receiver pulls up all this data from bottom to top to target application. Task of each layer is to wrap data from previous one to format appropriate to the same layer on receiver host and pass it to layer below. It does not care about the way that layer will process it. Very good analogy with postal service. We do not care what type of vehicles post uses to deliver our mail to recipient. We write a mail in a format (language) appropriate for receiver and put it in the envelope (transport layer), write source and destination address (network-routing level) and drop into PO box (data link layer - PO logistics). Physical layer (car, airplane) transmits it point to point where everything goes in back direction.

Again, NetBios or browser do not care about type cable or network protocol used as long as it is able to accomplish the task (like broadcasting).

In all good days of Windows for workgroups and Novell NetWare we had NetBEUI drivers installed for communications between computers in a workgroup on the local LAN (as NetBEUI is a non-routable protocol), IPX/SPX driver to access folders and printers on NetWare servers and TCP/IP to browse internet. And the same explorer application could use all protocols at the same time without problems.

Nowadays 99% of LAN use TCP/IP stack as Layer3/4, Ethernet as Layer 2, for Layer 1 - UTP for wired and Wi-Fi for Wireless. I also use powerline :-).

So when we a talking about NetBIOS we do not care about NetBIOS over NetBEUI (since windows XP came) or NetBIOS over SPX/IPX. We talking about NetBIOS over TCP/IP aka NBT.

Now if we trace how communication takes place we will see approximately following:

Browser application gets request to access \\DNS-323\Volume_1 share.
To resolve DNS-323 name it goes into netbios cache of resolved names and does not find it. Let's assume that LMHOSTS file is empty and WINS server is not configured at all.
Then as a last resort (before switching to DNS) it sends broadcast (using UDP/137) to local network asking "Who's name DNS-323?".
If DNS-323 is online it responds with unicast destined to the PC with response which contains its IP address.
After that PC places new entry into netbios cache with name-IP mapping (just like DNS resolution works)
Now as PC has IP destination IP address it needs to know MAC address of NIC card to which data should be tranferred. To do this it checks obtained IP with its own IP and address mask to figure out if that IP is in the same subnet.
If it is (which is very likely as broadcasts by default never forwarded by routers) then it checks its dynamic ARP table in hope to find IP-to-MAC mapping for DNS-323 IP address.
If that IP address happened to be on another network, PC will look for MAC address of Default Gateway (or gateway which was explicitly configured for that network in PC routing table using ROUTE PRINT command for example).
In either cases PC first checks its ARP table for existing entries. If there is no IP it is looking for, it performs ARP request (broadcast again) to the network asking "Who has X.X.X.X? Answer X.X.X.Y."
When DNS receives ARP request with its IP it sends back to the requester unicast response with its MAC address.
PC receives the response and adds IP-MAC mapping into its ARP table. Now application (browser) is ready to send a request to the NAS.
Formed request (say "obtain directory list of \Volume_1") is passed to netbios which establishes session with NAS and transmits datagrams to it.
NetBios requests in case of using TCP/IP are encapsulated into UDP datagrams with destination port 139 for session messages and port 138 for data itself.
Network layer (3) forms IP packets by adding IP header with source and destination IP, protocol type (UDP) and other fields.
Data link layer forms ethernet frames by addind ethernet header with source and destination MAC addresses taken form ARP table, type of protocol inside (IP in this case), append checksum and forwards it to Layer 1.
On layer 1 formed frame is finally transmitted to the recipient NIC over physical media.
I think I omit details of CDMA/CD or CDMA/CA and other L1 protocols operation  ;D.

Receiver (DNS-323) receives transmission and "pulls" it from L1 to L7 to obtain data for application to process and form a response.

So, where is a confusion?

I don't know if you're aware of this, but not only are ip addresses NOT required for local area network communications, they are NOT used, even when tcp/ip is the only network protocol in play.  In local area network communications it is the MAC addresses that are used to identify the source & destination hosts rather than the ip addresses.

That's a news for me. Having passed a bunch of cisco exams I haven't heard that if all the machines on the same LAN, IP or other L3 addresses are not necessary and may be omitted, and Layer 5 can pass data directly to Layer 2 for encapsulation and transmission  :o
Then why Microsoft bothered at all to create NetBEUI - simple small non-routable L3/L4 protocol aimed to work inside single LAN with source and destination netbios names as source and destination addresses for initial connection setup???? Did they also confuse OSI layers?

Could you explain please?

  

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rector

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Re: ip address
« Reply #50 on: June 01, 2010, 07:33:17 PM »

Correct, you have it as your master browser and when you turn it off, the network is confused.  I disabled the master browser capability of my two D-Link NAS boxes.

Hi, Thanks for that but can you tell me how? Thanks
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OlegMZ

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Re: ip address
« Reply #51 on: June 01, 2010, 08:06:44 PM »

Hi, Thanks for that but can you tell me how? Thanks

Here is the trick. If you have problems with accessing NAS by name or do not see it when you browse workgroups, it may me multiple master browsers problem. In this case if you run that utility (from link) you will see all list of your current netbios hosts, including master browsers. If you have only one workroup you should see only one master browser. If there is more than one - this is a problem.
If DNS-323 comes online first and by default assumes itself as a master browser with high priority, all other hosts should recognize it and join as a plain members. If one of your machines disregards NAS advertisements as master browser and makes itself MB as well - that is a problem.
If DNS-323 comes online after other PCs, one of which was MB, it ideally should force re-elections and take over MB role. If it just dumbly say "I am master browser", without any negotiations with other group members - this is a problem as again you have more than one MB.
If you plan to keep NAS online 24/7, then reboot other PCs and let it be MB. PCs should understand and "obey" NAS.
If you have another host that is online 24/7 and want to use it as a MB, either disable this feature on NAS (using funlpug) or configure different workgroup on it. Should help.

From what I see you had no problems resolving netbios name, so I really do not understang why file share was not accessible by typing \\dns-323\Volume_1 in Explorer (I mean NOT internet explorer).
Does \\x.x.x.x\Volume_1 work for you in this case - request by IP?

I have NAS running 24/7 with laptops on and off all the time - no big problems, although XP home had some issues resolving NAS name for Internet browser at one moment (access to web interface by netbios name). Access to file shares never was a problem at all.
My second notebook with XP Pro and DIFFERENT workgroup (also always master browser itself) never had any access problems either to network shares or to web interface of NAS.
Actually it just struck me that maybe that was the reason - different workgroup with NAS? And the reason why my laptop with XP home had issues at some point? Either NAS was too overloaded with amount of connections to bittorent and discarded advertisements from laptop coming online and trying to become MB, or just MB elections was not fully implemented on NAS and allowed many MB on the same network? That is an open question...


 
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rector

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Re: ip address
« Reply #52 on: June 01, 2010, 11:01:48 PM »

Here is the guy who made this job a little bit easier by creating simple netbios scanning app:

http://scottiestech.info/2009/02/14/how-to-determine-the-master-browser-in-a-windows-workgroup/

BTW, when you said you could ping NAS does it mean you could ping it by its name?

It you still have HOSTS file configured, you may also try to change NAS name there a little bit (make it DNS-323a for example) and try to play from there, to make sure NetBIOS and DNS names are different.

When you request NAS by entering \\dns-323\  somewhere in network neighborhood your machine AFAIK sends netbios broadcast asking "who the heck is DNS-323?" and expects to receive IP from NAS.
If you go to network neighborhood and try to browse list of workgroups, you get it from master browser, which should have DNS name-IP mapping obtained from NAS when it came online and sent broadcast "here I am, DNS-323, my IP is X.X.X.X".

Check you network with that tool (link) and see who is master browser on your network, workgroups etc. It is very strange that no computers see NAS netbios name. It means either it failed to send udp notification  broadcast on startup or it did not reach any destination. Don't you use any "non-standard" name for NAS by any chance (longer that 15 symbols, special characters etc.)? Is link and port to NAS reliable?

Hi, Thanks, this is getting pretty complex now, for me anyway?

This is whats happening:
Nas turned off
 
2 network pcs working as normal, win7 pc shown as master browser using lan scanner and nbtstat.

NAS rebooted, not on  network.

Ping NAS by IP, OK

Ping NAS by name, FAIL

Browser by IP, OK

Browser by name, FAIL

NBTSTAT has no connection with NAS

NET VIEW shows 2 pcs plus NAS

Lan scanner shows 2 pcs but FAILED to NAS (which is weird because cmd prompt does work by ip)

Entered NAS configuration, save settings, NAS now visible

Lan scanner shows NAS not as master browser, only win7 pc is.

Earlier in the day nbtstat showed NAS as master browser???????

Thanks

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gunrunnerjohn

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Re: ip address
« Reply #53 on: June 02, 2010, 05:00:28 AM »

That's the way master browser elections work, my problem is whenever the DNS-323 is on, it seems to win the elections.  And, for some reason, the DNS-321 and DNS-323 both assumed the master browser role, and that was causing response issues in the network.
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fordem

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Re: ip address
« Reply #54 on: June 02, 2010, 05:13:13 AM »

Could you explain please?
Congratulations on having passed your exams - now welcome to the real world - where 90% of what Cisco teaches will never be applied (unless you're lucky enough to land a job at an ISP or similar).  Just so that you are aware, I've been supporting wide area network installations that span, not just continents but oceans, for over a decade now, and in the beginning tcp/ip was not our protocol of choice, we do use it now, but my background as a network support engineer predates the worldwide adoption that exists today.

I'm not going to derail this thread any further - so you're going to have to do your own research, I will however point you in the right direction - go down to layers 1 & 2 and research them thoroughly.

You already know that before tcp/ip became popular, IPX/SPX & NetBEUI were the protocols of the day, so you know that tcp/ip & ip addresses are not a requirement for communication on a local area network - you already know that Layer2 appends MAC addresses, so you should recognize the reasons why - these are the addresses that govern what happens on the local network.
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OlegMZ

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Re: ip address
« Reply #55 on: June 02, 2010, 05:30:12 AM »

Hi, Thanks, this is getting pretty complex now, for me anyway?

This is whats happening:
Nas turned off
 
2 network pcs working as normal, win7 pc shown as master browser using lan scanner and nbtstat.

NAS rebooted, not on  network.

Ping NAS by IP, OK

Ping NAS by name, FAIL

Browser by IP, OK

Browser by name, FAIL

NBTSTAT has no connection with NAS

NET VIEW shows 2 pcs plus NAS

Lan scanner shows 2 pcs but FAILED to NAS (which is weird because cmd prompt does work by ip)


Do you mean that

nbtstat -a DNS-323  gives you nothing

net view \\DNS-323 gives you list of shares at the same time??


Interesting, and very strange. It means that netbios name was resolved, but no services visible? Makes no sense!
If access by name fails, it means NAS does not respond to netbios requests from this host. How about Win7 PC which was master browser at the time of NAS booted? It did not receive any netbios announcements either?


Entered NAS configuration, save settings, NAS now visible

Lan scanner shows NAS not as master browser, only win7 pc is.


So when you save config, NAS renegotiates its "netbios affairs" and honors Win 7 as a master browser? But when Win7 goes offline, takes over this role .... and becomes invisible??? Weird. What firmware version you are using?


Earlier in the day nbtstat showed NAS as master browser???????


I guess it was before reboot?

Try following. Go to NAS Setup -> Device. Change WORKGROUP setting to something different from the rest of workstations - NASWORKGROUP for example. Save config and reboot NAS - repeat all steps you followed before to reproduce NAS "invisibility". Check how everything goes.
My understanding that in this case Win7 will be MB for common workgroup, NAS will be MB for itself. Peace and sovereignty  ;D.
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jamieburchell

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Re: ip address
« Reply #56 on: June 02, 2010, 11:30:57 AM »

@rector your issue seems to be spread over two threads, confusingly.

Are you saying that you can always access your NAS via IP? If so, just stick to doing that.
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rector

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Re: ip address
« Reply #57 on: June 02, 2010, 03:29:32 PM »

@rector your issue seems to be spread over two threads, confusingly.

Are you saying that you can always access your NAS via IP? If so, just stick to doing that.

Hi,
Yes there was something similar on the other thread, where i joined in.

What Im saying is I can always access the NAS web page by IP address, not by name. 
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gunrunnerjohn

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Re: ip address
« Reply #58 on: June 02, 2010, 03:33:15 PM »

Workgroup browsing can have many causes, not just the NAS.  I have found that this box wants to be the master browser, I had to beat that out of it.  It's helped my network browsing not to have it trying to be the master browser.
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rector

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Re: ip address
« Reply #59 on: June 02, 2010, 04:17:53 PM »

Do you mean that

nbtstat -a DNS-323  gives you nothing

net view \\DNS-323 gives you list of shares at the same time??


Interesting, and very strange. It means that netbios name was resolved, but no services visible? Makes no sense!
If access by name fails, it means NAS does not respond to netbios requests from this host. How about Win7 PC which was master browser at the time of NAS booted? It did not receive any netbios announcements either?

So when you save config, NAS renegotiates its "netbios affairs" and honors Win 7 as a master browser? But when Win7 goes offline, takes over this role .... and becomes invisible??? Weird. What firmware version you are using?

I guess it was before reboot?

Try following. Go to NAS Setup -> Device. Change WORKGROUP setting to something different from the rest of workstations - NASWORKGROUP for example. Save config and reboot NAS - repeat all steps you followed before to reproduce NAS "invisibility". Check how everything goes.
My understanding that in this case Win7 will be MB for common workgroup, NAS will be MB for itself. Peace and sovereignty  ;D.


nbtstat -a DNS-323  gives you nothingxxxxxxxxxxxxxx           CORRECT
net view \\DNS-323 gives you list of shares at the same time??xxxxxxxxxxx    CORRECT

I tried to put a screenshot in here but it wont allow me
When i turned the win7 pc on this morning, NAS was already on, the following was noted with nbtstat

dns-323  <00>unique  registered
dns-323  <03>unique  registered
dns-323  <20>unique registered
   msbrowse <01> group registered
mshome  <id>  unique  registered
mshome <1e> group registered
mshome <00> group registered

MAC Adress 00-00-00-00-00-00

The win 7 pc was NOT the master browser

I changed the workgroup name as suggested and I got what I thought would happen, no sign of NAS anywhere. I was always of the opinion that all pcs on a network had to share the same network workgroup name????????

After resetting the NAS The win7 pc remained the same as not master browser but the NAS now is shown as also no master browser, but with no MAC address still????? is this normal

I am using firmware 1.08 which I have reflashed 

Thanks for your patience






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