On 03/26/2017 08:30 AM, Cindy-Sue
Causey wrote:
In the case I'm thinking, it's about manually adding multiple lines to
a file that I'm not completely remembering just now. Gut is saying
it's /etc/network/interfaces. Mine's almost empty so I don't have an
example to confirm that.
Typically user's put a second gateway option in the
/etc/network/interface file (which you talk about in the next
paragraph). This usually results in not understanding what the
gateway does.
What I encountered wasn't about declaring different values for
gateway, either. For whatever reasons due to innate [functionality],
it becomes a fail even if you declare the same gateway value for that
line within each new, separate block of declarations. Success is found
by declaring it once then omitting that line within any other new
blocks added over time.
While I've never put duplicate gateway information
in /etc/network/interfaces I, at one point when learning about
networking and setting it up in Debian, had put a gateway for each
subnet in the interfaces file (which is incorrect and resulted in
an error). A gateway, often called a "gateway of last resort"
tells the system how to reach subnets that it is not attached to.
That is the point of the gateway; it is the one place the system
can send packets to when it doesn't know where to go. If you
defined two gateways (meaning if this was allowed) you would be
back to square one, the system wouldn't know which gateway to send
the packet to. Defining two gateways could be an incorrect way of
saying you are defining two routes (most likely static routes).
Between my setup and cognition, I've never had anything stable enough
to test if it matters which block that gateway is declared. I've
wondered if it matters that it be in the first block, or if it just
needs to show up somewhere in that file. I was consciously putting it
in the first block because that seemed to be the *logical* thing to do
k/t having touched on programming 20 years ago at a local tech school.
I hadn't really thought about this myself. I've
always defined the gateway under the interface that is attached to
the subnet where the gateway resides. A.K.A. if I have two
networks:
auto eth0
iface inet eth0 static
address 192.168.0.2/24
auto eth1
iface inet eth1 static
address 10.1.10.2/24
And my gateway of last resort was on the 192.168.0 subnet then I
would define the gateway under that interface
auto eth0
iface inet eth0 static
address 192.168.0.2/24
gateway 192.168.0.1
It never occurred to me to see if it could be put anywhere in
the file. My hunch is it can and I guess I could take the 60
seconds to test it, but I'll leave that to more adventurous
people.
Thanks,
Joshua Schaeffer
I had simply done a route add so I reversed it with a route del.