Find the answer to your Linux question:
Results 1 to 8 of 8
Due to packet forwarding on my router I must disable DHCP and use static IPs on my LAN. This has always worked fine in the past but recently I have ...
Enjoy an ad free experience by logging in. Not a member yet? Register.
  1. #1
    Just Joined!
    Join Date
    Apr 2006
    Posts
    6

    How does DHCP Work?


    Due to packet forwarding on my router I must disable DHCP and use static IPs on my LAN. This has always worked fine in the past but recently I have been experimenting with SLAX, a server live CD based on slackware, as a mobile demo environment for my php scripts.

    The distro configures itself properly when I enable DHCP. But when I disable it I am unable to browse the web or connect to any im clients. However, I can ping local nodes, preform name resolution, and access my web based router config. This problem has arisen on multiple PCs and on two seperate networks.

    I contacted Tomas, the one man band for the project, who said nothing had changed and seems to have little motivation to help.

    I guess all I really need to know is how dhcp works and what files it modifies.

  2. #2
    Linux User stokes's Avatar
    Join Date
    Oct 2004
    Location
    UK
    Posts
    274
    Are you saying you can see PC's on your internal network but you can't see anything on the Internet? Sounds like a DNS resolution problem.

    Go to your router status page and make a note of the DNS servers allocated by your ISP. Then edit your /etc/resolv.conf and add the DNS servers in there.

    Code:
    nameserver 204.xxx.yyy.1
    nameserver 204.xxx.yyy.2
    The only problem is, you would lose these changes when you restart because Slax is a live distro. There may be some way of making these changes permenant, I really don't know with Slax, but I hope this helps ....
    Registered Linux user #389109
    My Semi-Linux Blog

  3. #3
    Linux User
    Join Date
    Apr 2005
    Location
    Ohio
    Posts
    326
    Also check to make sure you have a default route set.. The default route would be the IP address of your Router.. usually something like 192.168.1.1. Without a default route, you will not be able to access anything outside your local network.

    From your description I would say the problem is definately either the Default route or the DNS server settings if not both.

    Code:
    mail:/etc/network# route
    Kernel IP routing table
    Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
    192.168.1.0     *               255.255.255.0   U     0      0        0 eth1
    default         192.168.1.1     0.0.0.0         UG    0      0        0 eth1

    http://www.slackware.com/config/network.php

    http://slax.linux-live.org/doc_using...ax.php#network
    far...out

  4. $spacer_open
    $spacer_close
  5. #4
    Just Joined!
    Join Date
    Apr 2006
    Posts
    6
    I have already added a route/gateway and name servers. I cannot get past my router unless it is in dhcp mode. Not even to ping. However, I can preform name resolution when my router is set as the DNS server.

    I have a linksys router if that makes any difference.

  6. #5
    Linux User
    Join Date
    Apr 2005
    Location
    Ohio
    Posts
    326
    DHCP or Static IP's should make absolutely NO difference when it comes to IP communications.. having the right addressess in the right locations will make all the difference in the world..


    Internet
    |
    |
    <internet IP address set via DHCP from ISP>
    LINKSYS ROUTER
    <192.168.1.1> -internal Interface DHCP Server disabled
    |
    |
    |
    Workstation
    IP Address 192.168.1.2
    Netmask 255.255.255.0
    Broadcast Address 192.168.1.255
    Gateway 192.168.1.1
    DNS 192.168.1.1


    to check the addressing on your machine
    ifconfig -a
    mail:~# ifconfig -a
    eth1 Link encap:Ethernet HWaddr 00:02:B3:EE:5B:FD
    inet addr:192.168.1.2 Bcast:192.168.1.255 Mask:255.255.255.0
    inet6 addr: fe80::202:b3ff:feee:5bfd/64 Scope:Link
    UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
    RX packets:550718 errors:0 dropped:0 overruns:0 frame:0
    TX packets:16154 errors:0 dropped:0 overruns:0 carrier:0
    collisions:0 txqueuelen:1000
    RX bytes:84637889 (80.7 MiB) TX bytes:1263922 (1.2 MiB)
    Base address:0xdf80 Memory:ff8a0000-ff8c0000
    to check the default route
    route

    mail:~# route
    Kernel IP routing table
    Destination Gateway Genmask Flags Metric Ref Use Iface
    192.168.1.0 * 255.255.255.0 U 0 0 0 eth1
    default 192.168.1.1 0.0.0.0 UG 0 0 0 eth1
    to check dns

    more /etc/resolv.conf

    itg-debian:/etc# more /etc/resolv.conf
    nameserver 192.168.1.1
    to test connectivity

    Ping local address 192.168.1.2
    ping gateway 192.168.1.1
    ping internet host..

    imail:~# ping -c 3 72.14.205.99
    PING 72.14.205.99 (72.14.205.99) 56(84) bytes of data.
    64 bytes from 72.14.205.99: icmp_seq=1 ttl=255 time=2.49 ms
    64 bytes from 72.14.205.99: icmp_seq=2 ttl=255 time=1.50 ms
    64 bytes from 72.14.205.99: icmp_seq=3 ttl=255 time=1.29 ms

    --- 72.14.205.99 ping statistics ---
    3 packets transmitted, 3 received, 0% packet loss, time 2002ms
    rtt min/avg/max/mdev = 1.293/1.762/2.495/0.526 ms


    to test name resolution use dig to resolve some names..

    dig www.google.com
    mail:~# dig www.google.com

    ; <<>> DiG 9.2.4 <<>> www.google.com
    ;; global options: printcmd
    ;; Got answer:
    ;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 36732
    ;; flags: qr rd ra; QUERY: 1, ANSWER: 3, AUTHORITY: 0, ADDITIONAL: 0

    ;; QUESTION SECTION:
    ;www.google.com. IN A

    ;; ANSWER SECTION:
    www.google.com. 53507 IN CNAME www.l.google.com.
    www.l.google.com. 300 IN A 72.14.205.99
    www.l.google.com. 300 IN A 72.14.205.104

    ;; Query time: 40 msec
    ;; SERVER: 192.168.1.1#53(192.168.1.1)
    ;; WHEN: Tue Apr 11 16:16:13 2006
    ;; MSG SIZE rcvd: 84

    you need to figure out where the breakdown in your network is..

    DHCP is really irrelevant if your network settings are correct.
    far...out

  7. #6
    Just Joined!
    Join Date
    Apr 2006
    Posts
    6
    I just recieved a reply from the project manager for the distro and apparently it has been documented as a bug. So I guess I wasn't doing anything wrong after all. Now the only question is can anyone tell me how to fix it?

  8. #7
    Linux User
    Join Date
    Apr 2005
    Location
    Ohio
    Posts
    326
    http://slax.linux-live.org/forum/viewtopic.php?t=9963

    Yep it's listed as a bug.. looks like you will have to wait until the y figure it out, or configure your box to use DHCP.


    You are aware that you can usually configure a DHCP server to give aspecific IP address to a Certain machine on the network right ? IT's almost the same as having a static IP, since the box would always get the same address.


    Look into DHCP Reservations in your DHCP server. you will need the MAC address from the workstation you wish to assign a specific address to .

    Basically what you are doing is telling the DHCP server, When you see a DHCP request from this MAC address always give him THIS SPECIFIC IP Address..
    far...out

  9. #8
    Just Joined!
    Join Date
    Apr 2006
    Posts
    4

    Afaik

    Quote Originally Posted by farslayer
    http://slax.linux-live.org/forum/viewtopic.php?t=9963

    Yep it's listed as a bug.. looks like you will have to wait until the y figure it out, or configure your box to use DHCP.


    You are aware that you can usually configure a DHCP server to give aspecific IP address to a Certain machine on the network right ? IT's almost the same as having a static IP, since the box would always get the same address.


    Look into DHCP Reservations in your DHCP server. you will need the MAC address from the workstation you wish to assign a specific address to .

    Basically what you are doing is telling the DHCP server, When you see a DHCP request from this MAC address always give him THIS SPECIFIC IP Address..
    I have seen this functionality on a few different routers, but never on a linksys. I wish they would add it for ease of use, but I had a friend that explained to me why it would be redundant to have it there. I just dont remember the explanation or I would offer it here.

    IMHO,
    JS

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •