Remove the unspecified gateway from linux routing table

Rudy Zijlstra rudy at grumpydevil.homelinux.org
Tue Feb 17 12:11:45 UTC 2015


Hi Eugene,

See the response from Simon. I am also not familiar with 
redhat/centos/Fedora, so no idea where the script will be located. This 
script is called by dhclient to do that actual configuration work.

Cheers


Rudy

On 17-02-15 12:44, Eugène Ngontang wrote:
> Hi,
>
> To answer your questions :
> - which distribution is this? / *Fedora 18*
> - is dhcp provided by the a package from the distribution, or is it 
> hand compiled? / *Package*
> - which release of dhclient/dhcp is in use? / *Internet Systems 
> Consortium DHCP Server V3.0.5-RedHat & nternet Systems Consortium DHCP 
> Client 4.2.5*
> - dhclient typically calls a script to set the values. Is this script 
> correct and in place? / *Which script are you talking about here? The 
> dhclient init script???*
> *
> *
> *I've four other systems with exactly the same configuration and 
> connected to same dhcp server, which are working fine.
>
> *
> *
> [PRD][root at hostname]# cat /var/lib/dhclient/dhclient.leases
> lease {
> interface "eth0";
> fixed-address 10.10.10.22;
> option subnet-mask 255.255.255.240;
> option routers 10.10.10.17;
> option dhcp-lease-time 604800;
> option dhcp-message-type 5;
> option domain-name-servers 1.1.2.3,1.2.2.3;
> option dhcp-server-identifier 11.12.254.100;
> option nis-domain "xxx.priv";
> option domain-name "fr.mydomain.org <http://fr.mydomain.org>";
> renew 5 2015/02/20 22:26:22;
> rebind 1 2015/02/23 14:21:26;
> expire 2 2015/02/24 11:21:26;
> }
>
> [PRD][root at hostname]# cat 
> /var/lib/dhclient/dhclient-b6a65dbe-6524-4070-b4b7-3cb2b1333187-eth0.lease
> lease {
>   interface "eth0";
>   fixed-address 10.10.0.22;
>   option subnet-mask 255.255.255.240;
>   option dhcp-lease-time 604800;
>   option routers 10.10.10.17;
>   option dhcp-message-type 5;
>   option dhcp-server-identifier 11.12.254.100;
>   option domain-name-servers 1.1.2.3,1.2.2.3;
>   option nis-domain "xxx.priv";
>   option domain-name "fr.mydomain.org <http://fr.mydomain.org>";
>   renew 4 2015/02/19 14:33:43;
>   rebind 0 2015/02/22 15:00:34;
>   expire 1 2015/02/23 12:00:34;
> }
> lease {
>   interface "eth0";
>   fixed-address 10.10.10.22;
>   option subnet-mask 255.255.255.240;
>   option routers 10.10.10.17;
>   option dhcp-lease-time 604800;
>   option dhcp-message-type 5;
>   option domain-name-servers 1.1.2.3,1.2.2.3;
>   option dhcp-server-identifier 10.12.254.100;
>   option nis-domain "xxx.priv";
>   option domain-name "fr.mydomain.org <http://fr.mydomain.org>";
>   renew 4 2015/02/19 17:16:26;
>   rebind 0 2015/02/22 16:20:59;
>   expire 1 2015/02/23 13:20:59;
> }
>
> [PRD][root at hostname]# cat /etc/sysconfig/network-scripts/ifcfg-eth0
> # Generated by parse-kickstart
> UUID=b6a65dbe-6524-4070-b4b7-3cb2b1333187
> BOOTPROTO=dhcp
> DEVICE=eth0
> ONBOOT=yes
> IPV6INIT=no
> PERSISTENT_DHCLIENT=yes
>
> *
> *Are you seeing anything missing here??? Thanks.*
> *
> *
> *Regards,*
> *Eugène NG*
>
> 2015-02-17 12:16 GMT+01:00 Rudy Zijlstra 
> <rudy at grumpydevil.homelinux.org <mailto:rudy at grumpydevil.homelinux.org>>:
>
>     Hi Patrick,
>
>     I would suggist to find a strong cup of coffee ;)
>
>     DHCP is designed to work with no IP routing  in place at all.
>     Please consider that DHCP provides the computer with the IP
>     address it is to use. Any gateway is dependent on that IP address
>     and CANNOT be assigned before the IP address is known.
>
>     The correct question is indeed posed by the OP, which is why the
>     gateway is not applied from the DHCP response.
>
>     Some questions:
>     - which distribution is this?
>     - is dhcp provided by the a package from the distribution, or is
>     it hand compiled?
>     - which release of dhclient/dhcp is in use?
>     - dhclient typically calls a script to set the values. Is this
>     script correct and in place?
>
>     Cheers
>
>
>
>     Rudy
>
>
>     On 17-02-15 11:59, Patrick Trapp wrote:
>>     Perhaps I am not completely awake yet, but don't you have to have
>>     the default gateway in place to have network communication? That
>>     is, doesn't it have to precede the DHCP process?
>>
>>     It sounds to me like you just need to make the default route
>>     persistent so it will survive a reboot. How that is done depends
>>     on the flavor of Linux you are running.
>>
>>     Patrick
>>
>>
>>
>>     On Feb 17, 2015, at 4:43 AM, Eugène Ngontang <sympavali at gmail.com
>>     <mailto:sympavali at gmail.com>> wrote:
>>
>>>     Hi all,
>>>
>>>     I've a remote linux machine whose the routing table is :
>>>
>>>         [root at hostname]# route -n
>>>         Kernel IP routing table
>>>         Destination     Gateway Genmask         Flags Metric Ref  
>>>      Use Iface
>>>         0.0.0.0         0.0.0.0 0.0.0.0         U     0      0      
>>>      0 eth0
>>>         10.10.10.16    0.0.0.0 255.255.255.240 U     0      0      
>>>      0 eth0
>>>         169.254.0.0     0.0.0.0 255.255.0.0     U     1002   0      
>>>      0 eth0
>>>
>>>     The default gateway I should use is  10.10.10.17, and should be
>>>     given by a linux dhcp server. So to be able to connect to the
>>>     system I call someone on the site ask him to add the route
>>>     manually (**route add default gw 10.10.10.17**).
>>>     When the route has been added I can now connect to the system.
>>>     And once connected when I check the routing table again I have
>>>     this :
>>>
>>>         [root at hostname]# route -n
>>>         Kernel IP routing table
>>>         Destination     Gateway Genmask         Flags Metric Ref  
>>>      Use Iface
>>>         0.0.0.0         10.10.10.17  0.0.0.0         UG    0      0
>>>            0 eth0 (UG flag means it's up and is the gateway)
>>>         0.0.0.0         0.0.0.0 0.0.0.0         U     0      0      
>>>      0 eth0
>>>         10.10.10.16    0.0.0.0 255.255.255.240 U     0      0      
>>>      0 eth0
>>>         169.254.0.0     0.0.0.0 255.255.0.0     U     1002   0      
>>>      0 eth0
>>>
>>>     And when I restart the system, it boots without the right
>>>     default gateway, and I'm obliged to call again to set the route
>>>     manually. The dhclient lease file has the good **"option
>>>     routers"** taken from the dhcp server.
>>>
>>>     Now I'm trying to remove the unspecified route from the routing
>>>     table but each time I try I'm disconnected from the machine.
>>>
>>>     I've tried these different ways  :
>>>
>>>         route del -net 0.0.0.0 netmask 0.0.0.0 metric 0
>>>
>>>         route del default gw 0.0.0.0
>>>
>>>         route del -net 0.0.0.0 gw 0.0.0.0
>>>
>>>     The three attempts disconected me from the server, and the guy
>>>     at the other side tells me that each time I try to remove the
>>>     route the default route becomes a star (**default ***). I'm
>>>     obliged to let him add the route again mannualy, and when I'm
>>>     connected, and I restart the network I lose the connection again.
>>>
>>>     So my questions are :
>>>     1) Why does this unspecified default route come back every time?
>>>     2) How can I (what's the way to) remove it without spoiling the
>>>     routing table (losing the good  default gateway).
>>>
>>>     Thanks.
>>>
>>>     Regards,
>>>     Eugène NG
>>>
>>>
>>>
>>>     -- 
>>>     ngonta_e at epitech.net <mailto:ngonta_e at epitech.net>
>>>     sympavali at gmail.com <mailto:sympavali at gmail.com>
>>>     ------------------------------------------------------------
>>>     /*Aux hommes il faut un chef, et au*//* chef il faut des hommes!
>>>     L'habit ne fait pas le moine, mais lorsqu'on te voit on te juge!
>>>     */
>>>     _______________________________________________
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>>>     https://lists.isc.org/mailman/listinfo/dhcp-users
>>
>>
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>
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>
> -- 
> ngonta_e at epitech.net <mailto:ngonta_e at epitech.net>
> sympavali at gmail.com <mailto:sympavali at gmail.com>
> ------------------------------------------------------------
> /*Aux hommes il faut un chef, et au*//* chef il faut des hommes!
> L'habit ne fait pas le moine, mais lorsqu'on te voit on te juge!
> */
>
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