6:02 a.m.
Hi,
I am newbie to Fedora and I would like ask for a (for me important)
clarification regarding the assignment of the IP address of the computers
of my LAN.
Having problems to access to a repository located on another computer on my
LAN, I used, several times, the ping command to check the accessibility of
the nodes in the network ...
With my surprise, the answers that I received using the ping command (with
IP number) had not been consistent.
...an IP number available at a certain time was no longer available some
time after (and vice-verse);
And happened also that non-existent IP addresses in the network
occurred as available,
...some times....
Moreover, a test done with /sbin/ifconfig stated that some IP addresses
changed in the time.. ...
[angelo@zorro ~]$ /sbin/ifconfig
em0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST> mtu 1500
inet 10.0.0.6 netmask 255.255.255.0 broadcast 10.0.0.255
inet6 fe80::227:eff:fe1f:824c prefixlen 64 scopeid 0x20<link>
ether 00:27:0e:1f:82:4c txqueuelen 1000 (Ethernet)
RX packets 28131 bytes 30128278 (28.7 MiB)
RX errors 0 dropped 0 overruns 0 frame 0
TX packets 20820 bytes 2430096 (2.3 MiB)
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0
device interrupt 20 memory 0xf2100000-f2120000
[angelo@zorro ~]$ /sbin/ifconfig
em0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST> mtu 1500
inet 10.0.0.1 netmask 255.255.255.0 broadcast 10.0.0.255
inet6 fe80::227:eff:fe1f:824c prefixlen 64 scopeid 0x20<link>
ether 00:27:0e:1f:82:4c txqueuelen 1000 (Ethernet)
RX packets 44558 bytes 37451123 (35.7 MiB)
RX errors 0 dropped 0 overruns 0 frame 0
TX packets 33627 bytes 6296194 (6.0 MiB)
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0
device interrupt 20 memory 0xf2100000-f2120000
I didn't expect a such (for me) strange situation, and I would like to have
some explanation about it.
I can only think that all can be correlated to the dynamic assignment of
the IP address (DHCP), but the change of the IP happen also if the
computers are not rebooted.
If, is possible, I should like have a reference to documentation that can
explain this my problem.
Thank you
Regards
Angelo
4:55 a.m.
On Wed, 2014-10-08 at 06:42 +0800, Ed Greshko wrote:
The analogy of the telephone number and extension is a good one.
The
only thing I would add is that the extension (port/service) number is
generally fixed, standardized.
A list is kept by the IANA (Internet Assigned Numbers Authority) and
can be seen here....
http://www.iana.org/assignments/service-names-port-numbers/service-names-...
You can also see the default ports on your machine by looking
at /etc/services. Note that most of these are not normally active.
poc
11:40 p.m.
Thank you to all
Regards
Angelo
On Wed, Oct 8, 2014 at 1:42 AM, Ed Greshko <ed.greshko(a)greshko.com> wrote:
On 10/07/14 23:53, Angelo Moreschini wrote:
> thank you Ed, I learned many things from you. Actually I am a Linux
beginner ....
Welcome to Linux.
Mostly what has been discussed here is networking concepts. The same
applies to any network connected device just the location and way the
configuration information is stored and handled is different .
>
> Just another question, if I can, please:
> it exists some fix relation between the "port number" of the servers
and the theirs IP number ?
>
> It is some kind of correlation between them ?
The analogy of the telephone number and extension is a good one. The only
thing I would add is that the extension (port/service) number is generally
fixed, standardized.
A list is kept by the IANA (Internet Assigned Numbers Authority) and can
be seen here....
http://www.iana.org/assignments/service-names-port-numbers/service-names-...
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5:42 p.m.
On 10/07/14 23:53, Angelo Moreschini wrote:
thank you Ed, I learned many things from you. Actually I am a Linux
beginner ....
Welcome to Linux.
Mostly what has been discussed here is networking concepts. The same applies to any
network connected device just the location and way the configuration information is stored
and handled is different .
Just another question, if I can, please:
it exists some fix relation between the "port number" of the servers and the
theirs IP number ?
It is some kind of correlation between them ?
The analogy of the telephone number and extension is a good one. The only thing I would
add is that the extension (port/service) number is generally fixed, standardized.
A list is kept by the IANA (Internet Assigned Numbers Authority) and can be seen here....
http://www.iana.org/assignments/service-names-port-numbers/service-names-...
--
If you can't laugh at yourself, others will gladly oblige.
10:53 a.m.
thank you Ed, I learned many things from you. Actually I am a Linux
beginner ....
Just another question, if I can, please:
it exists some fix relation between the "port number" of the servers and
the theirs IP number ?
It is some kind of correlation between them ?
On Tue, Oct 7, 2014 at 1:40 PM, Ed Greshko <ed.greshko(a)greshko.com> wrote:
On 10/07/14 16:43, Angelo Moreschini wrote:
> I made it.
> The optut was:
> option dhcp-server-identifier 10.0.0.138;
> option dhcp-server-identifier 10.0.0.138;
> option dhcp-server-identifier 10.0.0.138;
> option dhcp-server-identifier 10.0.0.138;
> option dhcp-server-identifier 10.0.0.138;
> option dhcp-server-identifier 10.0.0.138;
> option dhcp-server-identifier 10.0.0.138;
> option dhcp-server-identifier 10.0.0.138;
> option dhcp-server-identifier 10.0.0.138;
> option dhcp-server-identifier 10.0.0.138;
>
> they look to be the same...
> however, are not able to interpret this value ...
10.0.0.138 is the IP address of the server providing your system with
configuration information.
Dave Ihnat had brought up the prospect that there could have been 2 DHCP
servers to explain the changes in your system's address. But, as you can
see, there is only one....
And......
>
> ------------------------
> here I write two complete records (the last two):
>
> lease {
> interface "em0";
> fixed-address 10.0.0.1;
> option subnet-mask 255.255.255.0;
> option routers 10.0.0.138;
> option dhcp-lease-time 3600;
> option dhcp-message-type 5;
> option domain-name-servers 10.0.0.138;
> option dhcp-server-identifier 10.0.0.138;
> option domain-name "Home";
> renew 2 2014/10/07 08:05:32;
> rebind 2 2014/10/07 08:29:41;
> expire 2 2014/10/07 08:37:11;
> }
> lease {
> interface "em0";
> fixed-address 10.0.0.3;
> option subnet-mask 255.255.255.0;
> option routers 10.0.0.138;
> option dhcp-lease-time 3600;
> option dhcp-message-type 5;
> option domain-name-servers 10.0.0.138;
> option dhcp-server-identifier 10.0.0.138;
> option domain-name "Home";
> renew 2 2014/10/07 08:34:07;
> rebind 2 2014/10/07 08:58:03;
> expire 2 2014/10/07 09:05:33;
> }
>
>
> what it mean ?
>
You can see that the server at 10.0.0.138 has provided you with 2
different IP addresses a different times. 10.0.0.1 and 10.0.0.3
(fixed-address).
There is no problem with your system. And, there is no problem with the
DHCP server. It just seems to be the policy of the entity responsible for
the DHCP server not to maintain the same IP address.
You can contact the person responsible for the DHCP server to see if they
can, or will, assign you a fixed IP address. If that is not possible, you
may have to use a Dynamic DNS service.
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5:40 a.m.
On 10/07/14 16:43, Angelo Moreschini wrote:
I made it.
The optut was:
option dhcp-server-identifier 10.0.0.138;
option dhcp-server-identifier 10.0.0.138;
option dhcp-server-identifier 10.0.0.138;
option dhcp-server-identifier 10.0.0.138;
option dhcp-server-identifier 10.0.0.138;
option dhcp-server-identifier 10.0.0.138;
option dhcp-server-identifier 10.0.0.138;
option dhcp-server-identifier 10.0.0.138;
option dhcp-server-identifier 10.0.0.138;
option dhcp-server-identifier 10.0.0.138;
they look to be the same...
however, are not able to interpret this value ...
10.0.0.138 is the IP address of the server providing your system with configuration
information.
Dave Ihnat had brought up the prospect that there could have been 2 DHCP servers to
explain the changes in your system's address. But, as you can see, there is only
one....
And......
------------------------
here I write two complete records (the last two):
lease {
interface "em0";
fixed-address 10.0.0.1;
option subnet-mask 255.255.255.0;
option routers 10.0.0.138;
option dhcp-lease-time 3600;
option dhcp-message-type 5;
option domain-name-servers 10.0.0.138;
option dhcp-server-identifier 10.0.0.138;
option domain-name "Home";
renew 2 2014/10/07 08:05:32;
rebind 2 2014/10/07 08:29:41;
expire 2 2014/10/07 08:37:11;
}
lease {
interface "em0";
fixed-address 10.0.0.3;
option subnet-mask 255.255.255.0;
option routers 10.0.0.138;
option dhcp-lease-time 3600;
option dhcp-message-type 5;
option domain-name-servers 10.0.0.138;
option dhcp-server-identifier 10.0.0.138;
option domain-name "Home";
renew 2 2014/10/07 08:34:07;
rebind 2 2014/10/07 08:58:03;
expire 2 2014/10/07 09:05:33;
}
what it mean ?
You can see that the server at 10.0.0.138 has provided you with 2 different IP addresses a
different times. 10.0.0.1 and 10.0.0.3 (fixed-address).
There is no problem with your system. And, there is no problem with the DHCP server. It
just seems to be the policy of the entity responsible for the DHCP server not to maintain
the same IP address.
You can contact the person responsible for the DHCP server to see if they can, or will,
assign you a fixed IP address. If that is not possible, you may have to use a Dynamic DNS
service.
--
If you can't laugh at yourself, others will gladly oblige.
3:43 a.m.
I made it.
The optut was:
option dhcp-server-identifier 10.0.0.138;
option dhcp-server-identifier 10.0.0.138;
option dhcp-server-identifier 10.0.0.138;
option dhcp-server-identifier 10.0.0.138;
option dhcp-server-identifier 10.0.0.138;
option dhcp-server-identifier 10.0.0.138;
option dhcp-server-identifier 10.0.0.138;
option dhcp-server-identifier 10.0.0.138;
option dhcp-server-identifier 10.0.0.138;
option dhcp-server-identifier 10.0.0.138;
they look to be the same...
however, are not able to interpret this value ...
------------------------
here I write two complete records (the last two):
lease {
interface "em0";
fixed-address 10.0.0.1;
option subnet-mask 255.255.255.0;
option routers 10.0.0.138;
option dhcp-lease-time 3600;
option dhcp-message-type 5;
option domain-name-servers 10.0.0.138;
option dhcp-server-identifier 10.0.0.138;
option domain-name "Home";
renew 2 2014/10/07 08:05:32;
rebind 2 2014/10/07 08:29:41;
expire 2 2014/10/07 08:37:11;
}
lease {
interface "em0";
fixed-address 10.0.0.3;
option subnet-mask 255.255.255.0;
option routers 10.0.0.138;
option dhcp-lease-time 3600;
option dhcp-message-type 5;
option domain-name-servers 10.0.0.138;
option dhcp-server-identifier 10.0.0.138;
option domain-name "Home";
renew 2 2014/10/07 08:34:07;
rebind 2 2014/10/07 08:58:03;
expire 2 2014/10/07 09:05:33;
}
what it mean ?
On Tue, Oct 7, 2014 at 11:05 AM, Ed Greshko <ed.greshko(a)greshko.com> wrote:
On 10/07/14 15:47, Angelo Moreschini wrote:
> for me the value is :
> lf
/var/lib/NetworkManager/dhclient-40d1ee1f-f089-4c90-afd9-e37016bc720c-em0.lease
>
> but I don't know about what file are you talking ...
cat
/var/lib/NetworkManager/dhclient-40d1ee1f-f089-4c90-afd9-e37016bc720c-em0.lease
| grep dhcp-server-identifier
Are they all the same?
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3:05 a.m.
On 10/07/14 15:47, Angelo Moreschini wrote:
for me the value is :
lf /var/lib/NetworkManager/dhclient-40d1ee1f-f089-4c90-afd9-e37016bc720c-em0.lease
but I don't know about what file are you talking ...
cat /var/lib/NetworkManager/dhclient-40d1ee1f-f089-4c90-afd9-e37016bc720c-em0.lease | grep
dhcp-server-identifier
Are they all the same?
--
If you can't laugh at yourself, others will gladly oblige.
2:47 a.m.
for me the value is :
lf
/var/lib/NetworkManager/dhclient-40d1ee1f-f089-4c90-afd9-e37016bc720c-em0.lease
but I don't know about what file are you talking ...
thank you
On Mon, Oct 6, 2014 at 4:22 PM, Ed Greshko <ed.greshko(a)greshko.com> wrote:
On 10/06/14 20:51, Dave Ihnat wrote:
> I would also wonder if there are dueling DHCP servers
> on the segment.
You should be able to determine if there are dueling DHCP servers by doing
a "ps -eaf | grep dhclient" and looking for the -lf parameter and then
examining the contents of the file.
In my case.... -lf
/var/lib/NetworkManager/dhclient-5ce325cb-5048-48d7-bdc0-457f278fe1f1-enp0s3.lease
Looking at the file you'd find "dhcp-server-identifier" and multiple
leases. If the IP address of "dhcp-server-identifier" changes, then you
have dueling DHCP servers.
--
If you can't laugh at yourself, others will gladly oblige.
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8:22 a.m.
On 10/06/14 20:51, Dave Ihnat wrote:
I would also wonder if there are dueling DHCP servers
on the segment.
You should be able to determine if there are dueling DHCP servers by doing a "ps -eaf
| grep dhclient" and looking for the -lf parameter and then examining the contents of
the file.
In my case.... -lf
/var/lib/NetworkManager/dhclient-5ce325cb-5048-48d7-bdc0-457f278fe1f1-enp0s3.lease
Looking at the file you'd find "dhcp-server-identifier" and multiple leases.
If the IP address of "dhcp-server-identifier" changes, then you have dueling
DHCP servers.
--
If you can't laugh at yourself, others will gladly oblige.
8:09 a.m.
On 10/06/2014 02:51 PM, Dave Ihnat wrote:
On Mon, Oct 06, 2014 at 02:22:42PM +0200, Ralf Corsepius wrote:
> On 10/06/2014 01:02 PM, Angelo Moreschini wrote:
> That's not unusual with DHCP. DHCP assigned IP-addresses usually
> have limited life-time until they expire. After expiration machines
> may be assigned a new IP-address.
However, I will point out that DHCP servers _tend_ to reassign the same
IP address to a machine renewing its lease.
Sure. But I've seen some implementations (on home-routers), which were
not doing so, but iterated through the whole pool of addresses, instead.
Ralf
7:51 a.m.
On Mon, Oct 06, 2014 at 02:22:42PM +0200, Ralf Corsepius wrote:
On 10/06/2014 01:02 PM, Angelo Moreschini wrote:
That's not unusual with DHCP. DHCP assigned IP-addresses usually
have limited life-time until they expire. After expiration machines
may be assigned a new IP-address.
However, I will point out that DHCP servers _tend_ to reassign the same
IP address to a machine renewing its lease. If you're seeing the address
change frequently, I would also wonder if there are dueling DHCP servers
on the segment. Determine what should be the definitive DHCP server and
make sure nothing else thinks it is also a DHCP server (e.g., other
computers, a firewall/router appliance, etc.)
If you want to access a machine under a static IP-address, you'd
have to set up your DHCP-server accordingly. How to do so would
depend upon you DHCP-server's implementation.
Well, actually, there are a couple of approaches:
o A DHCP server should be configured to only use a portion of the
available IP address range for the subnet. For instance, if you're
using a RFC1918 IPv4 subnet of 192.168.100.0/24, it would be common to
restrict DHCP to the range 192.168.100.100-199. Anything below or
above that range is available for static assignment.
o You can reserve IP addresses within the DHCP pool by MAC address.
This is usually used when you've a legacy IP assignment that is in
the DHCP pool and, for whatever reason, is difficult to change.
Cheers,
--
Dave Ihnat
dihnat(a)dminet.com
7:22 a.m.
On 10/06/2014 01:02 PM, Angelo Moreschini wrote:
Hi,
I can only think that all can be correlated tothe dynamic
assignmentof
the IP address (DHCP),
My guess would be the same.
but the change of the IP happen also if the
computers are not rebooted.
That's not unusual with DHCP. DHCP assigned
IP-addresses usually have
limited life-time until they expire. After expiration machines may be
assigned a new IP-address.
If you want to access a machine under a static IP-address, you'd have to
set up your DHCP-server accordingly. How to do so would depend upon you
DHCP-server's implementation.
Ralf
11:05 a.m.
On 10/07/2014 08:53 AM, Angelo Moreschini wrote:
Just another question, if I can, please:
it exists some fix relation between the "port number" of the servers
and the theirs IP number ?
No. Think of the IP as the machine's phone number, and the port number
as a particular service's extension. Thus, to connect to a web server,
you need to use the machine's IP address and the port number (or
extension) of the web server.
3481
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13 comments
6 participants
participants (6)
-
Angelo Moreschini -
Dave Ihnat -
Ed Greshko -
Joe Zeff -
Patrick O'Callaghan -
Ralf Corsepius