Music-PC not retaining IP Address

[thatguy]

Are you sure you don't have two DHCP servers on the network. If you are using an Airtel or BSNL DSL modem, it will have a DHCP server running by default. If your AP (I am assuming you have a modem and an access point) also runs a DHCP server, the kind of things you are seeing can happen.

EDIT: Oops. Just saw that Thad has already mentioned this point.

 

[sam9s]

Eve if we we have two DHCP running with modem connected to router and router providing the IPs, it should not create a problem, even I have Airtel Modem that runs its own DHCP. But the thing that we need to make sure is that the starting IP of two DHCPs should not be same. Usually for modem its 192.168.1.1 and for router its 192.168.0.1. If by any chance both are kept same, you would connect but the internet would not work ....

 

[manniraj]

@Thad,sam9

I use BBNL a private service provider over optical fiber. Hence no modem it is just some set top box kind thing which is connected to my Netgear wireless router. The technician configured on my router with the login/password information of my BBNL a/c.
Coming to the other point of setting the address reservation and saving and I think I did not restart the router. Ok let me try this option as well. Yesterday i checked the IP on my HTPC and it was retaining even after 2 to 3 restarts of the PC.

Thanks

 

[Thad E Ginathom]

Eve if we we have two DHCP running with modem connected to router and router providing the IPs, it should not create a problem, even I have Airtel Modem that runs its own DHCP. But the thing that we need to make sure is that the starting IP of two DHCPs should not be same.

It should create a problem --- and I realised this the hard way, from experience.

Yes, you could avoid that problem by ensuring that the range of IPs available for allocation by each DHCP server are entirely different, but that is a "solution" to a problem that never should have occurred in the first place.

Usually for modem its 192.168.1.1 and for router its 192.168.0.1. If by any chance both are kept same, you would connect but the internet would not work ....

This is not a question of "starting address" --- it is a matter (assuming netmask 255.255.255.0) of there being two separate networks. Devices on 192.168.0.0 and 192.168.1.0 cannot see each other. I recommend a good TCP/IP primer: it will explain it better than I can.

These days, everyone with a broadband connection had to do some network engineering, but without learning the basics of networking first, so there are a lot of wrong conceptions about.

Yesterday i checked the IP on my HTPC and it was retaining

Better to think about what is happening: your PC is not "retaining" the address, the DHCP server is giving it the same one as it had before. You may say that the end result is the same: I agree, but it helps to understand how

 

[sam9s]

It should create a problem --- and I realised this the hard way, from experience.

Yes, you could avoid that problem by ensuring that the range of IPs available for allocation by each DHCP server are entirely different, but that is a "solution" to a problem that never should have occurred in the first place.
This is not a question of "starting address" --- it is a matter (assuming netmask 255.255.255.0) of there being two separate networks. Devices on 192.168.0.0 and 192.168.1.0 cannot see each other. I recommend a good TCP/IP primer: it will explain it better than I can.

Well ... It should I guess, but it hasnt, (Never had actually) atleast not in my case, my both DHCPs are active. By starting address I mean when DHCP is made active, from which ip range should it start assigning the addresses. And that starting range for both DHCP (modem and router) should be different else it would create a problem. Pardon I could not use more technical language to explain the thing.

 

[sam9s]

Coming to the other point of setting the address reservation and saving and I think I did not restart the router. Ok let me try this option as well. Yesterday i checked the IP on my HTPC and it was retaining even after 2 to 3 restarts of the PC.
Thanks

Technically there is no need to restart the router, a simple save after adding the IPs should do. but if it works for you and now the IP is stable, good for you I guess.

 

[manniraj]

Better to think about what is happening: your PC is not "retaining" the address, the DHCP server is giving it the same one as it had before. You may say that the end result is the same: I agree, but it helps to understand how

Yes will do a check on when this IP of the HTPC/Music-PC is being retained or getting replaced with another this weekend. Also I am thinking would any of the apps like XBMC/Foobar will create or override this router IP as I have made these apps to load instead of windows explorer in each PC. I know it should not but just giving a wild guess. Will check this as well.

Thanks

 

[Thad E Ginathom]

No, an application cannot do that unless it surplants the entire operating system, not just the user interface. If it was doing that, you wouldn't need Windows in the first place. Please substitute "getting" for "retained" in your thinking. Your PC cannot actually "retain" a DHCP address

Well ... It should I guess, but it hasnt, (Never had actually) atleast not in my case, my both DHCPs are active. By starting address I mean when DHCP is made active, from which ip range should it start assigning the addresses. And that starting range for both DHCP (modem and router) should be different else it would create a problem. Pardon I could not use more technical language to explain the thing.

Mixed concepts error!

192.168.0.1 and 192.168.1.1 is like Chennai and Bangalore! Starting address, or range, for DHCP addresses is something else.

 

[sam9s]

^^ Yes they are, I agree, not sure what is mixed..?? For my router I have given the DHCP address to start assigning address from 192.168.0.1, and it does at random. Then I reserve those addresses so that it retains between machine reboots.

On my Modem as well I have not disabled DHCP, but have again provided the range from 192.168.1.1. Ofcourse it does not as no peripheral is connected. If I will give the same DHCP range to start with to my modem as well (192.168.0.1) as my router has, things would go bad and I would not be able to connect .... simple .... thats what I am trying to explain ...

 

[Thad E Ginathom]

^^ Yes they are, I agree, not sure what is mixed..?? For my router I have given the DHCP address to start assigning address from 192.168.0.1, and it does at random. Then I reserve those addresses so that it retains between machine reboots.

So, hosts on your 192.168.0.0 network send out a request for a DHCP server. 192.168.0.1 says hello and obliges. 192.169.1.1 does not oblige, because it does not get those requests.

On my Modem as well I have not disabled DHCP, but have again provided the range from 192.168.1.1. Ofcourse it does not as no peripheral is connected.

Fine, but no point, just as there would be no point in painting it blue, except that you might like blue, so that's fine. Equally, there would be no point in disabling it, but hey, I like blue .

If I will give the same DHCP range to start with to my modem as well (192.168.0.1) as my router has, things would go bad

Depending on how helpful its user interface is, it might not even accept that. "Addreses are not on this network," or something like it, would be a reasonable response.

EDIT: "DHCP server pool FROM 192.168.n.150 is not in LAN subnet 192.168.m.0." is what my D-Link says; "192.168.n.150 is not a valid address," is what my Airtel Betel modem says.

things would go bad and I would not be able to connect .... simple .... thats what I am trying to explain ...

You would not be able to connect because your DHCP clients would not be able to find a DHCP server and would not get their IP configuration. "Not be able to connect," would be the end result, but not the right diagnosis: give them static IPs and they would connect just fine.

It is simple, but not quite the way you think it is!

NB. I used to use the modem <---->[-WAN-router-LAN-]<---->wifi and wired devices configuration. Now I just use the LAN side and the "router" acts as a hub. Even simpler.

 

[sam9s]

So, hosts on your 192.168.0.0 network send out a request for a DHCP server. 192.168.0.1 says hello and obliges. 192.169.1.1 does not oblige, because it does not get those requests.

Yes thats corect, seem like.... as I said I could not find a more relevant technical language to say the same....

Fine, but no point, just as there would be no point in painting it blue, except that you might like blue, so that's fine. Equally, there would be no point in disabling it, but hey, I like blue .

There is a point, and the only point which I am trying to make is, that you can have two DHCPs enabled with modem and router, but you need to make sure that the IP range is different, thats it.

For this to happen, Technically what are the intricacies of a network that are going on in side the topology ........ is not what I am discussing .....

 

[Thad E Ginathom]

One Lan: One DHCP server ... is all.

Two Lans, two DHCP servers, if you must, is fine.

 

[sam9s]

^^ its not required, I know .... the only thing was if its there it does not create any issue ... (in this confined example I am discussing here)

 

[thatguy]

NB. I used to use the modem <---->[-WAN-router-LAN-]<---->wifi and wired devices configuration. Now I just use the LAN side and the "router" acts as a hub. Even simpler.

+1 to that. Actually, this *is* rocket science. I have so many home networks where both the modem and the AP are configured to work as layer three devices (with full array of L3 services running). Every packet passes through two NATs before it goes out.

I always try to explain to people to use the AP as a switch. Some get it, some don't

One Lan: One DHCP server ... is all.

Two Lans, two DHCP servers, if you must, is fine.

Couldn't have summed it up better. DHCP server is a database. And with databases, fewer the better. Keeping the machines consistent will become a nightmare pretty quickly.

 

[Thad E Ginathom]

+1 to that. Actually, this *is* rocket science.

Yes, it is!

I was actually quite proud when I set it up the other way, as two connected subnets, because it was probably as complex a task, for two pcs in a home, as any single thing I ever did at work supporting 40 people, over a hundred hosts, administering a firewall with VPNs ... ...

I was proud --- but it was unnecessary

I always try to explain to people to use the AP as a switch. Some get it, some don't

In the end, I did this out of sheer laziness. Always a great quality in a sys admin Glad to have confirmation.

Of course, it works very well: the "router" is just a switch/AP, but has its own IP so its admin interface is easily accessible. If I have to take it out, for some reason, and connect direct to the modem, I can do that with no PC reconfiguration (I use fixed IPs, it's just my habit, dating back to those days when a hosts file was part of my inventory and firewall control and management system) and it just works. Useful, for instance, when faced with ISP engineers who actually know less about networking than I do.

NB: I am not, and never was, a network engineer. I was a manager and a Unix sytems administrator. That required the practical knowledge mentioned above, and yes, I read the book, but for anything more, I had a freelance expert I'd call in.