I have just built (well, re-installed the OS on) a new system and have connected it to my LAN. It's running xubuntu 8.10 and uses the TV as its display device (probably irrelevant).
It all installed fairly smoothly and appeared to work OK except that the networking was a bit 'jerky'.
I then found that I couldn't ssh from the new machine to my desktop machine whereas other machines on the LAN could connect OK. It turned out that this was because the machine had the *same* IP address as my desktop machine. This of course explains the 'jerky' networking too!
However I really can't understand *why* it has decided its IP address is 192.168.1.4.
OK, some details, the router IP is 192.168.1.1 and it's the router that provides DHCP to the network. Most machines have static addresses, in particular my desktop machine (as noted above) is 192.168.1.4. The router is set up to start handing out DHCP addresses starting at 192.168.1.64 and this does work as there is a device (a VOIP server) which gets the address 192.168.1.64.
The 'new' xubuntu system has default network setup, I have given it the name 'lounge' (which is different from all others) and it acquires its IP address and networking setup automatically on startup.
So *how* is it getting 192.168.1.4 as its IP address?
OK, I can fix the problem fairly easily by giving it a fixed IP but I'd love to know what's gone wrong.
On Fri, 16 Jan 2009 19:09:41 +0000 Chris G cl@isbd.net allegedly wrote:
I have just built (well, re-installed the OS on) a new system and have connected it to my LAN. It's running xubuntu 8.10 and uses the TV as its display device (probably irrelevant).
It all installed fairly smoothly and appeared to work OK except that the networking was a bit 'jerky'.
I then found that I couldn't ssh from the new machine to my desktop machine whereas other machines on the LAN could connect OK. It turned out that this was because the machine had the *same* IP address as my desktop machine. This of course explains the 'jerky' networking too!
However I really can't understand *why* it has decided its IP address is 192.168.1.4.
OK, some details, the router IP is 192.168.1.1 and it's the router that provides DHCP to the network. Most machines have static addresses, in particular my desktop machine (as noted above) is 192.168.1.4. The router is set up to start handing out DHCP addresses starting at 192.168.1.64 and this does work as there is a device (a VOIP server) which gets the address 192.168.1.64.
The 'new' xubuntu system has default network setup, I have given it the name 'lounge' (which is different from all others) and it acquires its IP address and networking setup automatically on startup.
So *how* is it getting 192.168.1.4 as its IP address?
Are you /sure/ the router's DHCP pool starts at .64? If the machine in question is one that you have used before (as it appears to be from your email) then my guess is that the MAC address of the machine is recognised by the router as one that it has handed out an address to in the past and it is configured to hand out the same address to that MAC in all future requests. If your desktop has a fixed IP, then the router won't know about the conflict.
Check your router DHCP config.
Mick ---------------------------------------------------------------------
The text file for RFC 854 contains exactly 854 lines. Do you think there is any cosmic significance in this?
Douglas E Comer - Internetworking with TCP/IP Volume 1
http://www.ietf.org/rfc/rfc854.txt ---------------------------------------------------------------------
On Fri, Jan 16, 2009 at 08:27:07PM +0000, mbm wrote:
On Fri, 16 Jan 2009 19:09:41 +0000 Chris G cl@isbd.net allegedly wrote:
I have just built (well, re-installed the OS on) a new system and have connected it to my LAN. It's running xubuntu 8.10 and uses the TV as its display device (probably irrelevant).
It all installed fairly smoothly and appeared to work OK except that the networking was a bit 'jerky'.
I then found that I couldn't ssh from the new machine to my desktop machine whereas other machines on the LAN could connect OK. It turned out that this was because the machine had the *same* IP address as my desktop machine. This of course explains the 'jerky' networking too!
However I really can't understand *why* it has decided its IP address is 192.168.1.4.
OK, some details, the router IP is 192.168.1.1 and it's the router that provides DHCP to the network. Most machines have static addresses, in particular my desktop machine (as noted above) is 192.168.1.4. The router is set up to start handing out DHCP addresses starting at 192.168.1.64 and this does work as there is a device (a VOIP server) which gets the address 192.168.1.64.
The 'new' xubuntu system has default network setup, I have given it the name 'lounge' (which is different from all others) and it acquires its IP address and networking setup automatically on startup.
So *how* is it getting 192.168.1.4 as its IP address?
Are you /sure/ the router's DHCP pool starts at .64? If the machine in question is one that you have used before (as it appears to be from your email) then my guess is that the MAC address of the machine is recognised by the router as one that it has handed out an address to in the past and it is configured to hand out the same address to that MAC in all future requests. If your desktop has a fixed IP, then the router won't know about the conflict.
I think you're right though I don't *quite* understand exactly why the router did what it did. It was actually trivial to fix because the newly installed machine has two built in LAN connections, simply plugging the ethernet connection into the other one sorted everything and it got the expected address of 192.168.1.65.
As you say the machine *used* to be 192.168.1.4 and the router had remembered its MAC address and assigned it. Surely though the router should have been 'bright enough' to realise the MAC address had been re-assigned.
I still can't see where in the router to tell it not to remember MAC addresses and assign the same IP addresses to them.
Check your router DHCP config.
Mick
The text file for RFC 854 contains exactly 854 lines. Do you think there is any cosmic significance in this?
Douglas E Comer - Internetworking with TCP/IP Volume 1
http://www.ietf.org/rfc/rfc854.txt
On Fri, 16 Jan 2009 21:09:28 +0000 Chris G cl@isbd.net allegedly wrote:
I think you're right though I don't *quite* understand exactly why the router did what it did. It was actually trivial to fix because the newly installed machine has two built in LAN connections, simply plugging the ethernet connection into the other one sorted everything and it got the expected address of 192.168.1.65.
As you say the machine *used* to be 192.168.1.4 and the router had remembered its MAC address and assigned it. Surely though the router should have been 'bright enough' to realise the MAC address had been re-assigned.
Sorry - I don't understand that. The only information the DHCP server had was the request and the MAC address requesting the lease. I'm not sure how you expect the router the know that that MAC address had somehow been "re-used" and now needed a new IP address.
I still can't see where in the router to tell it not to remember MAC addresses and assign the same IP addresses to them.
Keep searching. If this is a domestic grade router, then somewhere there will be an option in the DHCP configuration something like "always assign the same IP address". Simply uncheck that option.
Mick
---------------------------------------------------------------------
The text file for RFC 854 contains exactly 854 lines. Do you think there is any cosmic significance in this?
Douglas E Comer - Internetworking with TCP/IP Volume 1
http://www.ietf.org/rfc/rfc854.txt ---------------------------------------------------------------------
On Fri, Jan 16, 2009 at 09:46:35PM +0000, mbm wrote:
On Fri, 16 Jan 2009 21:09:28 +0000 Chris G cl@isbd.net allegedly wrote:
I think you're right though I don't *quite* understand exactly why the router did what it did. It was actually trivial to fix because the newly installed machine has two built in LAN connections, simply plugging the ethernet connection into the other one sorted everything and it got the expected address of 192.168.1.65.
As you say the machine *used* to be 192.168.1.4 and the router had remembered its MAC address and assigned it. Surely though the router should have been 'bright enough' to realise the MAC address had been re-assigned.
Sorry - I don't understand that. The only information the DHCP server had was the request and the MAC address requesting the lease. I'm not sure how you expect the router the know that that MAC address had somehow been "re-used" and now needed a new IP address.
Well, because the IP address that *had* been assigned to that MAC address is already in use. The router has never assigned 192.168.1.4 itself, it has always been set to start giving out addresses from 192.168.1.64 upwards. I really don't see why it needs to even attempt to 'assign' addresses below 192.168.1.64, all the addresses below that are cast in stone elsewhere.
I still can't see where in the router to tell it not to remember MAC addresses and assign the same IP addresses to them.
Keep searching. If this is a domestic grade router, then somewhere there will be an option in the DHCP configuration something like "always assign the same IP address". Simply uncheck that option.
It a Draytek Vigor 2820n. The DHCP setup has:-
DHCP Server Configuration Enable Server Disable Server Relay Agent: 1st Subnet 2nd Subnet Start IP Address IP Pool Counts Gateway IP Address DHCP Server IP Address for Relay Agent
.... aaaaahhhhhhhhh!!!!!
There's a separate setup for "Bind IP to MAC", that's where it's remembered the old system's MAC address.
OK, both sorted *and* understood now! :-)
-
Chris G -
mbm