Router Question.

[SpringHeeledJack]

Afternoon gents

I was wondering about this these last few days and curiosity got the better of me and i duly checked on the net, but didn't seem to get a satisfactory answer.

My airport router displays itself variously as 192.168.0.1 or 2 or 3 for a time and varying periods as 195.xxx.xx.xx(various) for periods. These periods might last for days or weeks. There is no difference in speed or service whatever the configuration ID is, but why does it change and who is changing it, me or 'them' ? Any ideas appreciated.


Regards


SHJ

[Parapunter]

As I understand it Mr. Jack, and I'm quite happy to be put right by networking experts; 192.168.0.1 is a default IP address for a home router as set by the manufacturer. However, in the setting you described, the IP address is automatically changd in order to avoid IP address conflict I.e. pc1 logs on to 192.168.0.1 & then pc2 comes long, does same & so is given the next available IP address and so on.

Is this what it has come to? Answering IT questions on a Friday night? I used to go out & chase girls you know.:{

[rotorcraig]

If the router was acting as the DNS Server for your network I'd expect it to keep 192.168.0.1 for itself and allocate .2, .3, .4 etc to PCs coming online.

Assuming you're using windoze, try Start -> Run -> cmd to get to the command line prompt and then execute the command "ipconfig /all"

What do you see? I get the following (amongst a load of other blurb)...

Connection-specific DNS Suffix . :

Dhcp Enabled. . . . . . . . . . . : Yes
Autoconfiguration Enabled . . . . : Yes
IP Address. . . . . . . . . . . . : 192.168.0.3
Subnet Mask . . . . . . . . . . . : 255.255.255.0
Default Gateway . . . . . . . . . : 192.168.0.1
DHCP Server . . . . . . . . . . . : 192.168.0.1
DNS Servers . . . . . . . . . . . : 192.168.0.1

... which shows that the PC I'm using now sees my router on 192.168.0.1 as a DNS Server, has asked it for an IP address and been given .3 (another upstairs has got .2)

[Saab Dastard]

the IP address is automatically changd in order to avoid IP address conflict I.e. pc1 logs on to 192.168.0.1 & then pc2 comes long, does same & so is given the next available IP address and so on.

Not quite! Addresses are never changed to avoid conflicts.

The router is a multifunction device, and also operates as a DHCP server, which allocates IP addresses to clients from a pool of addresses. It never allocates the same address to different clients, but you are correct in saying that the next available IP address from the DHCP pool is allocated to the PC that next connects and requests an address.

Conflicts CAN occur if you mix DHCP allocated addresses with statically configured addresses, without due care and attention.

rotorcraig - note that it is DHCP that allocates IP addresses: DNS resolves names to IP addresses.

Note that the internal IP address of the router itself is automatically excluded from the range of DHCP addresses that can be allocated to clients. It should, therefore be fixed.

The external address of the router - i.e. the Public address - is assigned by the ISP, either statically (never changes) or, much more commonly, dynamically. In the latter case you may well see the Public IP address of the router change periodically.

Note that the internal address is usually set by the manufacturer as 192.168.x.x - this is one of a range of networks (192.168.0.0/16 to be precise) that has been set aside purely for use on internal networks, and is never visible on the public internet (as also are the 10.0.0.0/8 and 172.16.0.0/12).

So the 195.x.x.x address is actually a public IP address, which could well be the public address assigned by SHJ's ISP.

As for the router having a random internal IP address - either it is being messed with by a 3rd party, or it is seriously mis-configured and is not at all well! Do you find other problems with it?

SD

[SpringHeeledJack]

Thanks for your replies gents, yes it's sad when it's comes to IT on a friday night, but it's for a good cause :hmm:

Ok, i understand about the way the router changes depending on how many separate users there are on the network now, but what was going on when the address wasn't 192.168.0.x and was varying longer addresses (195.xxx.xxx.xx). It was almost as if the internal router address was 'external' and varying.

I turn off the airport after use as i'm not totally convinced about the safety of the wifi after spending several days with a scientist who was studying the effects some while back, so my external IP address changes sometimes several times a day. Might it have been coming from my provider ?

Otherwise my settings were as rotorcraig posted.



Thanks


SHJ

[rotorcraig]

rotorcraig - note that it is DHCP that allocates IP addresses
You're right of course :O I'll get my coat.

RC

[Saab Dastard]

My airport router displays itself variously as 192.168.0.1 or 2 or 3 for a time and varying periods as 195.xxx.xx.xx(various) for periods.

Where exactly is this information being displayed?

Rotorcraig - it's Friday evening, you are forgiven! ;)

[SpringHeeledJack]

Mr Saab

The information is displayed in my iStat widget in OS X, which shows at a glance various inner workings of the mac. In the network section it shows external IP address (semi-dynamic) and the static internal address 192.168.0.x etc.

Perhaps it's when i travel and use various other wifi's that the 192.xxx address becomes this longer address when i come back home. I know that when i'm on other networks the address will (and does) change, but felt that the longer 195.xxx.xx etc addresses (various) were either a virtual internal address generated by my ISP OR that someone might be watching....... :bored:

Nothing like a bit of paranoia to keep one occupied :}


Regards


SHJ

[Bushfiva]

This is a good example where mentioning "iStat" somewhere within the first sentence of the first posting would have been useful :-)

It's showing your computer's IP address, not your router's, and it's showing your external IP address. The external one may or may not change occasionally. The local one may change more frequently, especially if you routinely turn computers and routers on and off.

The router automagically routes data between devices on the internal network (your Mac) and between those devices and the external network.

When you take your computer elsewhere, the external IP will be the one assigned to the connection you are then using, and the internal one will also change. In some circumstances, it may be the same as the external IP address but that's quite unusual.

[SpringHeeledJack]

So......

I was off-line for a few hours at home and the internal network address shown is different to the 192.168.0.x and i looked up the address and it came up with....

Address block information:

OrgName: Internet Assigned Numbers Authority
OrgID: IANA
Address: 4676 Admiralty Way, Suite 330
City: Marina del Rey
StateProv: CA
PostalCode: 90292-6695
Country: US

NetRange: 169.254.0.0 - 169.254.255.255
CIDR: 169.254.0.0/16
NetName: LINKLOCAL
NetHandle: NET-169-254-0-0-1
Parent: NET-169-0-0-0-0
NetType: IANA Special Use
NameServer: BLACKHOLE-1.IANA.ORG
NameServer: BLACKHOLE-2.IANA.ORG
Comment: Please see RFC 3330 for additional information.
RegDate: 1998-01-27
Updated: 2002-10-14

Who are these people ? On iStat it shows this strange address, but in the system profiler it still shows me as 192.168 etc :confused:

Any thoughts ?


Thanks


SHJ

[Saab Dastard]

NetRange: 169.254.0.0 - 169.254.255.255
CIDR: 169.254.0.0/16
NetName: LINKLOCAL
NetHandle: NET-169-254-0-0-1
Parent: NET-169-0-0-0-0
NetType: IANA Special Use

This is a special reserved range (APIPA), for autoconfiguring PCs that have no fixed IP address and cannot contact a DHCP server.

It basically allows a bunch of PCs on a small network to autoconfigure themselves with IP addresses so that they can see each other on the local network.

Fine for a workgroup, but no use if you want to connect to the internet!

It is not routable on the public internet - like the 10.0.0.0, 172.16.0.0 and 192.168.0.0 networks - hence the DNS entries:

NameServer: BLACKHOLE-1.IANA.ORG
NameServer: BLACKHOLE-2.IANA.ORG

All it means is that your PC is configured to obtain a DHCP address but cannot contact a DHCP server - it then defaults to APIPA, as does Windows.

You might be interested in... (http://www.dummies.com/WileyCDA/DummiesTitle/TCP-IP-For-Dummies-5th-Edition.productCd-0764517600.html)

SD

[SpringHeeledJack]

Thanks for the explanation SD. I might well buy that book, although the title does seem a bit off-putting if one has a delicate ego like oneself :(:cool:

Btw, how do such companies (IANA) make any money ? Do they charge ISPs for usage of their servers and so on ?


Regards


SHJ