Centos – Static routes in route-eth0 ignored

centosiproute

Why might route-eth0 be ignored but route-eth1 not? Might be because eth0 is using DHCP and eth1 is statically-configured?

I have some static routes configured in

[16:20:06][root@zserver2:/etc/sysconfig/network-scripts]$ ls -al ro*
-rw-r--r-- 1 root root 104 Dec  6 15:49 route-eth0
-rw-r--r-- 1 root root 106 Dec  6 15:49 route-eth1

When I do a service network restart the routes for eth1 are activated but NOT those for eth0.

An ifup eth0 also ignores them, but an ifup-routes eth0 is just fine. What's the best way of getting it activated?

[16:18:36][root@zserver2:/etc/sysconfig/network-scripts]$ service network restart
Shutting down interface eth0:  Device state: 3 (disconnected)
                                                           [  OK  ]
Shutting down interface eth1:  Device state: 3 (disconnected)
                                                           [  OK  ]
Shutting down loopback interface:                          [  OK  ]
Bringing up loopback interface:                            [  OK  ]
Bringing up interface eth0:  Active connection state: activating
Active connection path: /org/freedesktop/NetworkManager/ActiveConnection/28
state: activated
Connection activated
                                                           [  OK  ]
Bringing up interface eth1:  Active connection state: activated
Active connection path: /org/freedesktop/NetworkManager/ActiveConnection/29
                                                           [  OK  ]

route info

[16:18:50][root@zserver2:/etc/sysconfig/network-scripts]$ route -n
Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
192.168.15.10   192.168.15.11   255.255.255.255 UGH   1      0        0 eth1
192.168.15.11   0.0.0.0         255.255.255.255 UH    0      0        0 eth1
192.168.15.11   192.168.15.91   255.255.255.255 UGH   1      0        0 eth1
192.168.15.0    0.0.0.0         255.255.255.0   U     1      0        0 eth0
0.0.0.0         192.168.15.1    0.0.0.0         UG    0      0        0 eth0

ifup eth0 manually

[16:19:03][root@zserver2:/etc/sysconfig/network-scripts]$ ifup eth0
Active connection state: activating
Active connection path: /org/freedesktop/NetworkManager/ActiveConnection/30
state: activated
Connection activated

route info

[16:19:35][root@zserver2:/etc/sysconfig/network-scripts]$ route -n
Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
192.168.15.10   192.168.15.11   255.255.255.255 UGH   1      0        0 eth1
192.168.15.11   0.0.0.0         255.255.255.255 UH    0      0        0 eth1
192.168.15.11   192.168.15.91   255.255.255.255 UGH   1      0        0 eth1
192.168.15.0    0.0.0.0         255.255.255.0   U     1      0        0 eth0
0.0.0.0         192.168.15.1    0.0.0.0         UG    0      0        0 eth0

ifup-routes eth0 manually

[16:19:56][root@zserver2:/etc/sysconfig/network-scripts]$ ./ifup-routes eth0
[16:20:00][root@zserver2:/etc/sysconfig/network-scripts]$ route -n
Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
192.168.15.1    192.168.15.90   255.255.255.255 UGH   5      0        0 eth0
192.168.15.10   192.168.15.11   255.255.255.255 UGH   1      0        0 eth1
192.168.15.10   192.168.15.1    255.255.255.255 UGH   5      0        0 eth0
192.168.15.11   0.0.0.0         255.255.255.255 UH    0      0        0 eth1
192.168.15.11   192.168.15.91   255.255.255.255 UGH   1      0        0 eth1
192.168.15.0    0.0.0.0         255.255.255.0   U     1      0        0 eth0
0.0.0.0         192.168.15.1    0.0.0.0         UG    0      0        0 eth0

Config files are:

ifcfg-eth0

[16:30:26][root@zserver2:/etc/sysconfig/network-scripts]$ cat ifcfg-eth0
DEVICE=eth0
TYPE=Ethernet
UUID=76ef8242-9e22-4a29-93f3-a142d1460c87
ONBOOT=yes
NM_CONTROLLED=yes
BOOTPROTO=dhcp
DEFROUTE=yes
IPV4_FAILURE_FATAL=yes
IPV6INIT=no
NAME="System eth0"
HWADDR=00:25:90:86:71:E0
PEERDNS=yes
PEERROUTES=yes
LAST_CONNECT=1386361279

ifcfg-eth1

[16:30:35][root@zserver2:/etc/sysconfig/network-scripts]$ cat ifcfg-eth1
DEVICE=eth1
TYPE=Ethernet
UUID=647f66bd-67b2-4e9a-b5a5-4280ad677b9a
ONBOOT=yes
NM_CONTROLLED=yes
BOOTPROTO=none
DEFROUTE=yes
IPV4_FAILURE_FATAL=yes
IPV6INIT=no
NAME="System eth1"
IPADDR=192.168.15.91
PREFIX=32
HWADDR=00:25:90:86:71:E1
LAST_CONNECT=1386361279

Best Answer

The problem is likely timing. Among other things, the ifup script does this:

puts eth0 in an "up" state
starts dhclient to obtain an IP address
loads static routes from route-eth0

The problem is that ifup doesn't wait for dhclient to get an IP address before trying to load your static routes, and the kernel won't install a route for an interface without an IP address configured on it.

If you must use DHCP, one solution is to let dhclient add the routes for you. Per the manpage for dhclient-script(8) from CentOS 6.5:

Immediately after dhclient brings an interface UP with a new IP address, subnet mask, and routes, in the REBOOT/BOUND states, it will check for the existence of an executable* /etc/dhcp/dhclient-up-hooks script, and source it if found. This script can handle DHCP options in the environment that are not handled by default. A per-interface /etc/dhcp/dhclient-${IF}-up-hooks script will override the generic script and be sourced when interface $IF has been brought up.

You should be able to make this work by creating a /etc/dhcp/dhclient-eth0-up-hooks script containing the following:

/etc/sysconfig/network-scripts/ifup-routes eth0

Related Solutions

Debian Networking – Fixing `RTNETLINK answers: File exists` Error

I got it that I had to flush the device before bringing it up:

# ip addr flush dev eth1

Clearing manually set interface configuration information like this is mentioned in the Ubuntu Server Guide.

Restoring lost network routes after loss of network

A routing table will make your route permanent (to avoid adding it again/manually after a switch failover); First, create a named routing table. As an example, we could use "mgmt".

echo '200 mgmt' >> /etc/iproute2/rt_tables

Just for an extended detail about the solution, above, the kernel supports many routing tables and refers to these by unique integers numbered 0-255. A name, mgmt, is also defined for the table. Below, a look at a default /etc/iproute2/rt_tables follows, showing that some numbers are reserved. The choice in this answer of 200 is arbitrary; one might use any number that is not already in use, 1-252.

# reserved values
255     local
0       unspec

Second, edit your post-up rule (under /etc/network/interfaces) like this

  post-up ip route add 10.1.0.0/24 dev eth0.101 table mgmt
  post-up ip route add default via 10.1.2.1 dev eth0.101 table mgmt
  post-up ip rule add from 10.1.0.0/24 table mgmt
  post-up ip rule add to 10.1.0.0/24 table mgmt

Alternatively an other solution could be a background bash script checking for the route existence and adding it back if it's missing, the script could check the result of ip route add 10.1.0.0/24 via 10.1.2.1 dev eth0.101 the script could be setup in a loop or a cron

ip route add 10.1.0.0/24 via 10.1.2.1 dev eth0.101
if [ $? -eq 0 ]; then
    echo "Route added again"
    sleep 10;
    command-to-call-the-script-again
else
    echo "Route exists"
    sleep 10;
    command-to-call-the-script-again
fi

Source: what is the best way to add a permanent route?

route info

ifup eth0 manually

route info

ifup-routes eth0 manually

Best Answer

Related Solutions

Debian Networking – Fixing `RTNETLINK answers: File exists` Error

Restoring lost network routes after loss of network

Related Question