On 08/08/2016 14:22, Ashish Yadav wrote:

Hi,

You can define your default gateway in "/etc/sysconfig/network" file,

GATEWAY="192.168.1.1"

After that, restart network services.

# systemctl restart network

It's defined .... and it is in routing table ... the only thing added is: #route add default gw 192.168.1.1 dev enp3s0

Basically I have 2 default gateways or, if you wish, the same gateway is defined as default but on different interface

# ip route show

...

default via 192.168.1.1 dev enp3s0 default via 192.168.1.1 dev enp2s0 169.254.0.0/16 dev enp2s0 scope link metric 1002 169.254.0.0/16 dev enp3s0 scope link metric 1003 192.168.1.0/24 dev enp2s0 proto kernel scope link src 192.168.1.12 192.168.1.0/24 dev enp3s0 proto kernel scope link src 192.168.1.13

--Regards Ashishkumar S. Yadav

On Mon, Aug 8, 2016 at 4:35 PM, Levente Birta blevi.linux@gmail.com wrote:

...

Hi

There is a Centos 7 up-to-date box with 2 interfaces, let's say 192.168.1.12 - enp2s0, 192.168.1.13 on enp3s0. Default gateway on enp2s0.

The gateway is pfsense, IP is 192.168.1.1 with 2 WAN connections

On the gateway the outgoing traffic is routed by source ip to different WAN, 192.168.1.12 to WAN1 and 192.168.1.13 to WAN2

On the centos box are set all the route and routing rules:

route-enp2s0: 192.168.1.0/24 dev enp2s0 src 192.168.1.12 table t2 default via 192.168.1.1 dev enp2s0 table t2

route-enp3s0: 192.168.1.0/24 dev enp3s0 src 192.168.1.13 table t3 default via 192.168.1.1 dev enp3s0 table t3

rule-enp2s0: from 192.168.1.12/32 table t2 to 192.168.1.12/32 table t2

rule-enp3s0: from 192.168.1.13/32 table t3 to 192.168.1.13/32 table t3

All work when I add #route add default gw 192.168.1.1 dev enp3s0

And that way I have :

# ip route show default via 192.168.1.1 dev enp3s0 default via 192.168.1.1 dev enp2s0 169.254.0.0/16 dev enp2s0 scope link metric 1002 169.254.0.0/16 dev enp3s0 scope link metric 1003 192.168.1.0/24 dev enp2s0 proto kernel scope link src 192.168.1.12 192.168.1.0/24 dev enp3s0 proto kernel scope link src 192.168.1.13

But how can I add achieve this only with ip route command ... without route? Can I add this in any config files (ex: route-enp2s0)?

Thanks

-- Levi _______________________________________________ CentOS mailing list CentOS@centos.org https://lists.centos.org/mailman/listinfo/centos

---

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On 09/08/2016 06:56, Anthony K wrote:

On 08/08/16 21:05, Levente Birta wrote:

...

But how can I add achieve this only with ip route command ... without route? Can I add this in any config files (ex: route-enp2s0)?

Hi Levente.

The iproute2 man page for each command is rather well documented on CentOS 7. For instance, to view the specifics of *ip route*, type *man ip-route*. On older versions of CentOS, all commands to ip have been lumped into *m**an ip*.

Also, would you care to explain why you'd want to have the same subnet on 2 interfaces of the same device? If both networks had a host with the same IP, and another host on either one of the networks needed to talk to one of them, how would the router know which one to talk to?

I have encountered this before where one company acquired another and they both had same subnet IP's. Before we renumbered one of the subnets, we resolved this via iptables mungling and policy routing. So, it's doable, but why when there's plentiful supply of RFC1918 IP addresses?

As I said in the initial message the centos box need to access the internet on both interfaces, the gateway in function of source IP ( the two IPs allocated on the centos box on two interfaces ) route the traffic on different WAN connection.

My problem simply is that on the Centos box I cannot access the internet on the second interface (i.e. second WAN connection) without the command: #route add default gw 192.168.1.1 dev enp3s0

I'd like to mention that any traffic on the LAN is going in/out on the right interface ... just the internet cannot be reached on the second interface.

What I don't understand why the route command allow to add a second default gateway with different interface, but the ip route command doesn't?

Thanks

On 09/08/2016 15:47, Jonathan Billings wrote:

On Tue, Aug 09, 2016 at 10:58:40AM +0300, Levente Birta wrote:

...

What I don't understand why the route command allow to add a second default gateway with different interface, but the ip route command doesn't?

You can only have one default gateway.

It sounds to me like you want to use both interfaces, which are both on the same subnet and would connect to the same gateway, as some sort of load-balanced network, where traffic is evenly distributed across both interfaces? Or did I mis-read your initial question?

No, there is no load-balancing.... It is a server on the LAN with two NICs, two IPs and I want to access the internet on both interfaces ... which means, practically, different WAN connection, but from the server's point of view doesn't matter, the routing to different WAN is a job of gateway's. And as I said in the initial message I achieved this ... :) The question is how can I achieve this with more elegant way, because the "route" command is deprecated anyway.

So, again: Centos 7 2 NICs enp2s0-192.168.1.12 enp3s0-192.168.1.13 default gateway on enp2s0 is 192.168.1.1, defined in /etc/sysconfig/network

Which other way (preferred with "ip route") can I add this, but: #route add default gw 192.168.1.1 dev enp3s0 ????

Thanks Levi

On 08/09/2016 12:03 PM, John R Pierce wrote:

those are both the same network, and the default gateway is a global thing. packets forwarded to 192.168.1.1 could use either 192.168.1.12 or .13, as they are all the same. in reality, they will use the first match they find.

Generally, but not necessarily. What Birta is trying to accomplish is called "multi-homing." The oracle document I linked to is one of the shortest, accurate descriptions of its configuration on Red Hat derived systems that I've come across.

On Wed, Aug 10, 2016 at 09:29:15AM +0300, Levente Birta wrote:

I read the document again ... and this talk about accessing this multi-homed host from the internet... I have all this configured and working!

You say this is working because of the output here?

# ip route show default via 192.168.1.1 dev enp3s0 default via 192.168.1.1 dev enp2s0 169.254.0.0/16 dev enp2s0 scope link metric 1002 169.254.0.0/16 dev enp3s0 scope link metric 1003 192.168.1.0/24 dev enp2s0 proto kernel scope link src 192.168.1.12 192.168.1.0/24 dev enp3s0 proto kernel scope link src 192.168.1.13

On 10/08/16 16:29, Levente Birta wrote:

And as I said this problem is resolved too ... I asked for another way to achieve this

When you add a default gateway with:

route add default gw 192.168.1.1 dev enp3s0

you'll note that you now have 2 routes with the same metric of 0 (use route -n to see the metric field - couldn't get ip route to show me the metric).

When using ip route command, you need to specify a different metric otherwise it won't take. To me, ip route is doing the right thing as having 2 gateways with the same metric will confuse the routing process.

If you need to use ip route to add another default gateway, make sure to use a different metric:

ip route add 0/0 via 192.168.1.1 dev enp3s0 metric <different_from_other_one>

ak.

------------------------------------

PS: In my virtual environment *[0]*, the routing tables for tables t2 and t3 appeared incomplete. The route specified in the route files for network 192.168.1.0/24 was missing - most likely cause it was already in the main routing table. Only the default route appeared in the tables

$ cat /etc/sysconfig/network-scripts/route-enp0s3 192.168.1.0/24 dev enp0s3 src 192.168.1.12 table t2 default via 192.168.1.1 dev enp0s3 table t2

$ cat /etc/sysconfig/network-scripts/route-enp0s8 192.168.1.0/24 dev enp0s8 src 192.168.1.13 table t3 default via 192.168.1.1 dev enp0s8 table t3

$ ip r l t t2 default via 192.168.1.1 dev enp0s3

$ ip r l t t3 default via 192.168.1.1 dev enp0s8

*[0]* - https://imagebin.ca/v/2r5NJgNEqSgQ

On 8/9/2016 11:51 AM, Birta Levente wrote:

I do all this and working on LAN ... all traffic go in/out on the proper interface ... the problem is when I try to access the internet on the second interface ....

how do you try and access the 'internet on the second interface' when its all the same subnet?? its the same internet, isn't it?

On 08/09/2016 11:51 AM, Birta Levente wrote:

If I add "#route add default gw 192.168.1.1 dev enp3s0" all is good, but cannot add that in route-iface file or with "ip route" ....

Are you using the "network" or the "NetworkManager" service to configure your network? I haven't verified that the route-<interface> files are supported by NetworkManager.

If you are using the older "network" service, then you might be getting the syntax of the route-<interface> file wrong. If you included the contents of your ifcfg-<interface> and route-<interface> files, we could check.

Generally, I'm quite certain that the document I provided describes how to accomplish specifically what you're trying to accomplish.