default gateway not set when using bond0 interface

This is my /etc/network/interfaces file:

auto bond0
iface bond0 inet manual
    address 10.66.7.11/24
    gateway 10.66.7.1
    bond-mode 802.3ad
    bond-slaves eth2 eth3
    bond-miimon 100
    bond-downdelay 200
    bond-updelay 400
    bond-lacp-rate 1
    up ifconfig bond0 10.66.7.11/24 up

when I bring the bond0 interface up, it works, but the default gateway is not set

# route -n
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
10.66.7.0       0.0.0.0         255.255.255.0   U     0      0        0 bond0

I have to set the default gateway manually, and then everything works fine:

route add default gw 10.66.7.1 bond0

#route -n
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface  
0.0.0.0         10.66.7.1       0.0.0.0         UG    0      0        0 bond0
10.66.7.0       0.0.0.0         255.255.255.0   U     0      0        0 bond0

why is my default gateway not set automatically, when I have it defined in the /etc/network/interfaces file ?

Asked By: Martin Vegter

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Source

Among multiple ifupdown implementations, I’ll consider it’s ifupdown (implementation "v1") and the interfaces(5) configuration as seen on Debian.

The bond0 stanza should not use the keyword manual:

The manual Method

This method may be used to define interfaces for which no
configuration is done by default. Such interfaces can be configured
manually by means of up and down commands or /etc/network/if-*.d
scripts.

which will configure bond0‘s bond properties (on Debian probably through the ifenslave package which adds plugin scripts in /etc/network/if-*.d) but not IP properties.

So nothing is done: both address and gateway options are ignored but manual commands brought through up scripts are executed, such as:

up ifconfig bond0 10.66.7.11/24 up

which manually runs a command which happens to be adding an address on bond0: that’s why bond0 has an address, the LAN route automatically added by the kernel from this address, and no gateway.

The keyword static (which will still do what the manual method would do but will also configure IPv4 with inet static) should have been used:

The static Method

This method may be used to define Ethernet interfaces with statically
allocated IPv4 addresses.

to have ifupdown configure IP addresses and the default gateway on it.

So simply replace manual with static and remove the non-needed up entry. The configuration should then be:

auto bond0
iface bond0 inet static
    address 10.66.7.11/24
    gateway 10.66.7.1
    bond-mode 802.3ad
    bond-slaves eth2 eth3
    bond-miimon 100
    bond-downdelay 200
    bond-updelay 400
    bond-lacp-rate 1
Answered By: A.B