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Thread: How to setup a dhcp client on a bridge interface

  1. #1
    ajhart1 NNTP User

    Red face How to setup a dhcp client on a bridge interface

    Hi guy's, if really being struggling with this. First, I have a cisco router witch provides me with internet(static ip's), followed a x86 microtik router that has a dhcp server for local computers(10.1.1.1/24) and wireless end users. Now I have a transparent caching proxy server between the cisco and the microtik router that runs in bridge mode.
    Here was the process I went through creating the bridge:


    1. At the console login as root.
    o This step will disconnect the server enough to stop a remote session, so this has to be done at the server.
    2. Install Brigde-Utils first:
    o yast -i bridge-utils
     You may be asked for the install media.
    3. Go to the network folder:
    o cd /etc/sysconfig/network
     Note that interface set-up information is in configuration files that are preceded by 'ifcfg-<interface name>' and will be auto loaded based on that naming standard.
    4. Backup the network configuration by making a folder and copying the contents there:
    o mkdir ../network.old
    o cp -Rv * ../network.old
    5. Remove the existing configuration:
    o rm ifcfg-*
     This will not kill the network connection till the service is reloaded and the configuration files are re-read
    6. Create a new configuration file as such:
    o touch ifcfg-br0
     This creates a blank file of given name.
    o gedit ifcfg-br0
     At a terminal session from inside Gnome (the desktop) this starts the text editor. Create a file that looks like this:

    STARTMODE=auto
    BOOTPROTO=static
    IPADDR=10.1.1.10
    NETMASK=255.255.255.0
    BRIDGE='yes'
    BRIDGE_PORTS='eth0 eth1'
    BRIDGE_AGEINGTIME='300'
    BRIDGE_FORWARDDELAY='0'
    BRIDGE_HELLOTIME='2'
    BRIDGE_MAXAGE='20'
    BRIDGE_PATHCOSTS='19'
    BRIDGE_STP='on'
    7. Restart networking:
    o /etc/init.d/network restart
    The bridge is working perfectly fine with the static ip of 10.1.1.10, but when I ping the microtik router that has the dhcp server at 10.1.1.1, it gives me a timeout.
    Now the only reason I can think of why is that dhcp server does not see the proxy server's static ip in the dhcp pool. The only way solving this is for the mikrotik server assigning the proxy server with a ip.
    How can I configure the bridge with a dhcp client?
    Any advice will mean the world to me and very much appreciated!
    Thanks in advance.
    ajhart

  2. #2
    Join Date
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    Default Re: How to setup a dhcp client on a bridge interface

    Howdy,
    First thing is to clarify terminology. I assume by "proxy server" you're referring to your bridge device, but proxy servers are special animals not to be confused with bridging or forwarding devices -- Proxy devices terminate network network connections, then act on behalf of the client whereas the other devices simply allow network traffic to pass through so the original client's identity is preserved.

    In fact, for starters I'd recommend you look at your bridging device's filtering (firewalling) policies. If you think that DHCP is the problem (are DHCP clients on the other side of the device not communicating? - Reload the network connection to purge and request a new DHCP lease), make sure your bridging device specifically isn't blocking broadcasts (else you might have to configure a DHCP relay), but you may have to test other connectivity, too... like DNS, network authentication, etc.

    Am not sure your reasons for this bridging device, but if it's not a security issue I'd test a config to allow "any/all." If that works, then go back to your current or more restrictive config and slowly open up the specific ports you need.

    hTH,
    Tony

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