Completely Different range of IPs obtained from Dhcp server
Linux - NetworkingThis forum is for any issue related to networks or networking.
Routing, network cards, OSI, etc. Anything is fair game.
Welcome to LinuxQuestions.org, a friendly and active Linux Community.
You are currently viewing LQ as a guest. By joining our community you will have the ability to post topics, receive our newsletter, use the advanced search, subscribe to threads and access many other special features. Registration is quick, simple and absolutely free. Join our community today!
Note that registered members see fewer ads, and ContentLink is completely disabled once you log in.
If you have any problems with the registration process or your account login, please contact us. If you need to reset your password, click here.
Having a problem logging in? Please visit this page to clear all LQ-related cookies.
Introduction to Linux - A Hands on Guide
This guide was created as an overview of the Linux Operating System, geared toward new users as an exploration tour and getting started guide, with exercises at the end of each chapter.
For more advanced trainees it can be a desktop reference, and a collection of the base knowledge needed to proceed with system and network administration. This book contains many real life examples derived from the author's experience as a Linux system and network administrator, trainer and consultant. They hope these examples will help you to get a better understanding of the Linux system and that you feel encouraged to try out things on your own.
Click Here to receive this Complete Guide absolutely free.
Completely Different range of IPs obtained from Dhcp server
Currently I am facing a strange problem.
- If I connect my windows laptop to internet(ethernet), it happily gets an ip, gateway, dns etc through dhcp and works fine. These are the values fetched:
IP Address: 184.108.40.206
Subnet Mask: 255.255.254.0
Default Gateway: 220.127.116.11
DNS Servers: 18.104.22.168, 22.214.171.124
- When I try to connect my linux deskop to the internet, it gets a complete different set of ip, gateway etc. and I am also not able to access internet. I am completely lost for any logical reason.
Can somebody please explain?
I am listing some info that I collected from linux machine
The values obtained are:
eth0 Link encap:Ethernet HWaddr 00:16:36:57:6C:A2
inet addr:10.10.0.247 Bcast:10.10.1.255 Mask:255.255.254.0
inet6 addr: fe80::216:36ff:fe57:6ca2/64 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:143048 errors:0 dropped:0 overruns:0 frame:0
TX packets:420 errors:0 dropped:0 overruns:0 carrier:0
RX bytes:15166544 (14.4 MiB) TX bytes:46409 (45.3 KiB)
Interrupt:17 Base address:0xe000
The set of dns addresses are same (as those obtained for windows).
Even from this 10.* range of address, I am able to ping Gateway obtained for windows configuration (126.96.36.199).
[root@farfaraway debug]# route
Kernel IP routing table
Destination Gateway Genmask Flags Metric Ref Use Iface
10.10.0.0 * 255.255.254.0 U 0 0 0 eth0
link-local * 255.255.0.0 U 0 0 0 wlan0
192.168.0.0 * 255.255.0.0 U 0 0 0 wlan0
default 10.10.0.1 0.0.0.0 UG 0 0 0 eth0
[root@farfaraway debug]# traceroute 188.8.131.52
traceroute to 184.108.40.206 (220.127.116.11), 30 hops max, 40 byte packets
1 (18.104.22.168) 0.866 ms 0.936 ms 1.052 ms
tethereal -i eth0
206.350249 QuantaCo_f9:23:5f -> Broadcast ARP Who has 22.214.171.124? Tell 126.96.36.199
206.416877 QuantaCo_f9:23:5f -> Broadcast ARP Who has 188.8.131.52? Tell 184.108.40.206
206.430226 QuantaCo_f9:23:5f -> Broadcast ARP Who has 220.127.116.11? Tell 18.104.22.168
206.464941 CiscoLin_e8:37:21 -> Broadcast ARP Who has 10.10.128.1? Tell 10.10.128.44
206.513564 QuantaCo_f9:23:5f -> Broadcast ARP Who has 22.214.171.124? Tell 126.96.36.199
206.607127 QuantaCo_f9:23:5f -> Broadcast ARP Who has 188.8.131.52? Tell 184.108.40.206
From the tethereal output, it is pretty much visible, that machine can see packets on 10.10.* and 77.222.* n/w.
I really want to get the internet working on my machine, but clueless as of know. Can somebody please provide some pointers?
Last edited by sanjay.krk; 08-01-2008 at 04:22 AM.
Reason: some incorrect informatino (different subnet mask) removed).
Still stuck and not able to solve this problem.
But I got some additional information. May be some networking guru can see some pattern .
--- On Windows ----
C:\Documents and Settings\Administrator>arp -a 220.127.116.11
Interface: 18.104.22.168 --- 0x2
Internet Address Physical Address Type
22.214.171.124 00-16-36-f9-23-5f static
---- On Linux ----
[root@farfaraway ~]#arp 10.10.0.1
Address HWtype HWaddress Flags Mask Iface
10.10.0.1 ether 00:16:36:F9:23:5F C eth0
Basically, the 'mac address' of gateway I obtain on both the machines is same (though ips are different).
I have had this problem happen to me.. it is not your linux machine but rather the modem. For some reason my modem will not give me access to the internet if I just switch machines. What you need to do is plug your desktop and power off the modem for a few seconds, turn it back on and it will resend your mac over to the dhcp server.
the best solution is to get a router so you don't have to do this procedure constantly every time that you switch machines.
Its no surprise the MAC addresses of the gateway device are the same - the wire goes to the same place regardless of which machine you plug into the jack.
Some intelligent switches (with some layer 3 capabilities) and routers can be configured to allow only a single MAC address during the span of a DHCP lease or other period. Your PC gets a public (usable) IP address, while you get an RFC 1918 (private) IP address otherwise. It seems like you're getting put on a VLAN under these circumstances.
Get the MAC address of your PC, and spoof your Linux system's Ethernet MAC address to the same as the PC, and try to obtain a lease after that.
This may be a simple programming problem with their switch/router, or could be a security configuration they've employed.
Excellent. I thought it would. I think it is clear what they are doing.
Originally Posted by Mr. C.
Place a NATing router between the port and your systems. Then, it presents itself as one MAC address, giving you the ability to use multiple systems.
Ok, thats useful information, may be I will try it some day.
As of know, I just want to work on setting my linux machine as the host for Internet connection sharing (ICS). The only other machine in the n/w (sharing this internet connection) will be running windows.
Last edited by sanjay.krk; 08-02-2008 at 10:31 PM.
Reason: Quotes placed correctly