Multiple IPs on Multiple NICs same subnet

2

1

So, I've got two NICs:

eth0
eth1

and I have multiple IP addresses assigned to each:

auto lo
iface lo inet loopback
allow-hotplug eth0
iface eth0 inet static
    address 10.0.0.194
    netmask 255.255.255.0
    gateway 10.0.0.1
    network 10.0.0.0

auto eth0:0
allow-hotplug eth0:0
iface eth0:0 inet static
    address 10.0.0.253
    netmask 255.255.255.0

auto eth0:1
allow-hotplug eth0:1
iface eth0:1 inet static
    address 10.0.0.252
    netmask 255.255.255.0

auto eth0:2
allow-hotplug eth0:2
iface eth0:2 inet static
    address 10.0.0.251
    netmask 255.255.255.0

auto eth1
allow-hotplug eth1
iface eth1 inet static
    address 10.0.0.74
    netmask 255.255.255.0
    gateway 10.0.0.1
    network 10.0.0.0

auto eth1:0
allow-hotplug eth1:0
iface eth1:0 inet static
    address 10.0.0.105
    netmask 255.255.255.0

auto eth1:1
allow-hotplug eth1:1
iface eth1:1 inet static
    address 10.0.0.104
    netmask 255.255.255.0

auto eth1:2
allow-hotplug eth1:2
iface eth1:2 inet static
    address 10.0.0.106
    netmask 255.255.255.0

I've also setup ip route like so:

sudo ip route add 10.0.0.0/24 dev eth0 table eth0
sudo ip route add default via 10.0.0.1 dev eth0 table eth0

sudo ip route add 10.0.0.0/24 dev eth1 table eth1
sudo ip route add default via 10.0.0.1 dev eth1 table eth1

sudo ip rule add from 10.0.0.194 table eth0
sudo ip rule add from 10.0.0.74 table eth1

Now when I execute the following commands, everything works fine I get back my external IP:

curl --interface eth0  http://ipecho.net/plain ; echo
curl --interface eth0:0  http://ipecho.net/plain ; echo
curl --interface eth0:1  http://ipecho.net/plain ; echo
curl --interface eth0:2  http://ipecho.net/plain ; echo
curl --interface eth1  http://ipecho.net/plain ; echo

However, when I run:

curl --interface eth1:0  http://ipecho.net/plain ; echo

Nothing happens. I've obviously messed up my routes or something. Can anyone help me out? Thanks.

ip route

default via 10.0.0.1 dev eth0 
10.0.0.0/24 dev eth0  proto kernel  scope link  src 10.0.0.194 
10.0.0.0/24 dev eth1  proto kernel  scope link  src 10.0.0.74

route -n

Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
0.0.0.0         10.0.0.1        0.0.0.0         UG    0      0        0 eth0
10.0.0.0        0.0.0.0         255.255.255.0   U     0      0        0 eth0
10.0.0.0        0.0.0.0         255.255.255.0   U     0      0        0 eth1

EDIT:

So I found this, which is what I'm trying to do however, I don't want to specify any subnets. I just want it to round-robin the requests.

https://unix.stackexchange.com/questions/111293/load-balancing-among-multiple-virtual-network-interfaces

Hugh

Posted 2014-03-15T13:05:01.110

Reputation: 71

Have you set reverse path filtering off ? Its possible that traffic for eth1:0 is leaving one interface and coming back on the other. – davidgo – 2015-12-25T22:38:14.250

It sounds like you want a strong host model, which Linux just doesn't do.

– David Schwartz – 2015-12-25T22:41:00.547

Read my answer here: https://superuser.com/questions/1056054/using-dhcp-to-get-two-different-ip-addresses-for-two-nics-on-one-machine/1056060#1056060 - if you are not interested in bonding the two interfaces (making them look like 1 to the OS and also the receiving end), then it should explain things.

– LawrenceC – 2016-04-29T19:59:40.913

I'm guessing you are statically assigning your IP addresses, no? If you are, wouldn't you agree that posting the contents of /etc/network/interfaces is more informative than the output of ifconfig? I'd like to see how you actually have it manually configured. – jason – 2014-03-22T21:37:18.550

Wich distribution are you using? – Nils – 2014-03-23T22:00:33.360

What happens when you add explicit routing rules for all outgoing IP addresses? – Daniel B – 2014-03-24T13:03:48.437

Where is your initial connection(s) to the Internet? Which interface(s)? What are configuration details for such interface(s). – jason – 2014-03-24T23:53:49.730

Please explain why you have those IPs assigned. BTW: ip route get $IP will show you which interface will be used for that target IP. – Nils – 2014-03-28T21:32:44.363

Because its on AWS VPC – Hugh – 2014-03-28T21:46:52.980

Whatever it is you are trying to do, this is not the way to do it. Linux fundamentally follows the weak end system model (IP addresses belong to machines) and your configuration only makes sense under a strong end system model (IP addresses belong to interfaces).

– David Schwartz – 2014-03-28T21:55:26.523

Follow the bonding link in my answer. Everything is explained there... – Nils – 2014-04-03T14:01:24.560

Answers

1

I think you should read up about bonding interfaces.

If you want to load-balance using two interfaces the system you are connecting to has to "speak" exactly the same LB-protocol as you do.

Else you will loose packets.

Nils

Posted 2014-03-15T13:05:01.110

Reputation: 347

Can I still choose which IPs are used for outbound requests over that bond for each interface? Thanks. – Hugh – 2014-03-24T17:45:40.923

4@James Why would you want to do that? – Nils – 2014-03-28T15:40:51.900

0

If you are trying to load balance between two physical nics, then you might want to look into a bridged connection. The reason why you your second nic is not responding, is because the route you have for it is the same route you have for your first nic. So, all the virtual interfaces under nic 2 including the nic itself, is trying to route out to through the first nic, which isn't possible unless you bridge the nic's. It is easy under Linux to create bridge connections, and you can even make virtual bridges for the virtual interfaces as well.

Frostalf

Posted 2014-03-15T13:05:01.110

Reputation: 429

-2

Having several NICs connected to the same network might just get you extra collisions. Unless you configure the network carefully, it won't work. And it is quite improbable that the last link is your bottleneck; if it is, you are probably better off with a high speed NIC (and upstream hardare to match).

The whole IP network idea is that you have one NIC on each net. A set up like the one you have is extremely out of line with what is normally done, and (if even legal) is unlikely to have ever been put through it's paces and any misbehaviour fixed.

vonbrand

Posted 2014-03-15T13:05:01.110

Reputation: 2 083

Ok, I'll trying putting the interfaces on different subnets. Once I've done that how can I load-balance outbound requests over those two interfaces? – Hugh – 2014-03-23T19:37:37.087

3I don't see how having multiple NICs on the same network would cause any problems at all. Packet collisions don't exist on a fully switched network. Address collisions won't occur with the OPs configuration. – Daniel B – 2014-03-24T12:59:49.237

Asked: 2014-03-15T13:05:01.110

Viewed: 5 019 times

Active: 2016-11-13T18:30:04.210