[CentOS] Need help with Linux networking interfaces and NIC bonding

Thu Oct 4 13:44:06 UTC 2018

I don't know if this is your situation or not but I have found in my bonding testing that failover can take what I consider to be an inordinate amount of time (as in up to 50 seconds).  Were you "patient" (possibly using an altered definition of the term) to see if ping would eventually reply.

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________________________________________
From: CentOS <centos-bounces at centos.org> on behalf of Sean Son <linuxmailinglistsemail at gmail.com>
Sent: Thursday, October 4, 2018 12:44 AM
To: CentOS mailing list
Subject: [EXTERNAL] [CentOS] Need help with Linux networking interfaces and NIC bonding

Hello everyone

I am running into some strange issues when configuring networking
interfaces on my physical server running Centos 7.5. Let me give you an
overview of what's going on:

We have a physical server, running CentOS 7.5. This server has one 4 port
NIC and one 2 port NIC and a Dell IDRAC port.  The first port of the 4 port
NIC, em1, is used for Management traffic. The first port of the 2 port NIC,
is used for the second port in the  NIC bond, device p6p2.  The second
port on the 4 port NIC, device em2 is the first, port on the NIC bond.

These interfaces are using Static IPs.

Here is my /etc/sysconfig/network-scripts/ifcfg-em1 file. Please keep in
mind that I have changed the IPs and MAC addresses in the files for
security reasons:

ifcfg-em1:

TYPE="Ethernet"
PROXY_METHOD="none"
BROWSER_ONLY="no"
BOOTPROTO="none"
DEFROUTE="yes"
IPV4_FAILURE_FATAL="no"
IPV6INIT="yes"
IPV6_AUTOCONF="yes"
IPV6_DEFROUTE="yes"
IPV6_FAILURE_FATAL="no"
IPV6_ADDR_GEN_MODE="stable-privacy"
NAME="em1"
UUID="bbb2f9c2-141b-4a99-ab1e-328551aae612"
DEVICE="em1"
ONBOOT="yes"
IPADDR="192.168.56.50"
PREFIX="24"
GATEWAY="192.168.56.1"
DNS1="192.168.126.10"
DNS2="192.168.220.10"
IPV6_PRIVACY="no"
NM_CONTROLLED=no

as for the ifcfg-bond0 (the configuration file for the NIC bond, which is
bond0):

DEVICE=bond0
NAME=bond0
TYPE=Bond
ONBOOT=yes
BOOTPROTO=none
IPADDR=192.168.56.70
PREFIX=24
BONDING_MASTER=yes
BONDING_OPT="mode=1 miimon=100"
TYPE=Ethernet

and the ifcfg-slave1 configuration file, which is the first slave port for
the NIC bond, this corresponds to em2:

DEVICE=em2
HWADDR="c8:2f:87:fg:2a:31"
ONBOOT=yes
TYPE=Ethernet
BOOTPROTO=none
MASTER=bond0
SLAVE=yes

and the ifcfg-slave2 configuration file , which corresponds to the second
slave port for the NIC bond, which is interface p6p2:

DEVICE=p6p2
HWADDR="00:6a:d7:7c:e8:09"
BOOTPROTO=none
ONBOOT=yes
TYPE=Ethernet
MASTER=bond0
SLAVE=yes

I created a custom routing policy for the NIC bond, bond0. Here is the
configuration for the routing  policy:

route-bond0:

192.168.56.0/24 dev bond0 src 192.168.56.70 table t1
default via 192.168.56.1 dev bond0 table t1

and the rule-bond0 file:

table t1 from 192.168.56.70

as for the routing table:

Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use
Iface
0.0.0.0        192.168.56.1    0.0.0.0         UG    0      0        0 bond0
192.168.56.0    0.0.0.0         255.255.255.0   U     0      0        0
bond0
192.168.56.0    0.0.0.0         255.255.255.0   U     0      0        0 em1
169.254.0.0     0.0.0.0         255.255.0.0     U     1002   0        0 em1
169.254.0.0     0.0.0.0         255.255.0.0     U     1008   0        0
bond0

now here is the scenario I am dealing with:

This linux server is used for monitoring purposes. We have Nagios, Cacti
and other tools installed on it. There are a few things I have noticed and
I want help on:

1) Whenever I ping any of the devices on our network, from this server, the
traffic goes out from the management port. I do not want the traffic to go
out of the management port. I want it to go out through the active port of
the NIC bond.  How do I configure the networking so that all primary
network traffic flows to and from the NIC bonded interfaces?  I only want
the management port to be used for SSH purposes and well, management of the
server.

2) I have configured the NIC bond in active-backup mode. I notice that when
I used another computer to do a continuous ping to the NIC bond, and then I
disable one of the slave interfaces of the bond, the ping drops and it does
not failover to the backup slave interface and turn  into the active one.
It also causes any pings to the management  port to drop as well.  Then
when I disable slave2, and enable slave1, the traffic does not fail over to
slave1 and the ping  continuously fails.  It is only when I enable both
slave interfaces and then either restart the networking  using systemctl
restart network, or reboot the server, the networking resumes and the pings
succeed again.  What steps should I take to fix this issue?  Should I even
use active-backup mode with the NIC bond or is there a better mode I should
use?

3) Ive tested the networking, by changing  the VLAN of the NIC bonded
ports, on the switch, to a different VLAN, and it caused the management
port to stop responding to ping. Why is this and how do I fix that if I
decide to one day use two different VLANs for Management and the NIC bond
ports?

Thank you for all of your help in advance!

Sean
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