Appendix: Configuring Linux to Recognize Ethernet Devices for Multiple Network Interfaces - SAP HANA on AWS

Appendix: Configuring Linux to Recognize Ethernet Devices for Multiple Network Interfaces

Follow these steps to configure the Linux operating system to recognize and name the Ethernet devices associated with the new elastic network interfaces created for logical network separation, which were discussed earlier in this paper.

  1. Use SSH to connect to your SAP HANA host as ec2-user, and sudo to root.

  2. Remove the existing udev rule; for example: 

    hanamaster:# rm -f /etc/udev/rules.d/70-persistent-net.rules

  3. Create a new udev rule that writes rules based on MAC address rather than other device attributes. This will ensure that on reboot, eth0 is still eth0, eth1 is eth1, and so on. For example: 

    hanamaster:# cat <<EOF >/etc/udev/rules.d/75-persistent-net- generator.rules
# Copyright (C) 2012 Amazon.com, Inc. or its affiliates. # All Rights Reserved.
#
# Licensed under the Apache License, Version 2.0 (the "License").
# You may not use this file except in compliance with the License.
# A copy of the License is located at #
#	    https://aws.amazon.com/apache2.0/ #
# or in the "license" file accompanying this file. This file is # distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS
# OF ANY KIND, either express or implied. See the License for the
# specific language governing permissions and limitations under the
# License.
# these rules generate rules for persistent network device naming
SUBSYSTEM!="net", GOTO="persistent_net_generator_end" KERNEL!="eth*", GOTO="persistent_net_generator_end" ACTION!="add", GOTO="persistent_net_generator_end" NAME=="?*", GOTO="persistent_net_generator_end"

# do not create rule for eth0
ENV{INTERFACE}=="eth0", GOTO="persistent_net_generator_end" # read MAC address
ENV{MATCHADDR}="\$attr{address}" # do not use empty address
ENV{MATCHADDR}=="00:00:00:00:00:00",
GOTO="persistent_net_generator_end"
# discard any interface name not generated by our rules ENV{INTERFACE_NAME}=="?*", ENV{INTERFACE_NAME}=""
# default comment
ENV{COMMENT}="elastic network interface" # write rule IMPORT{program}="write_net_rules"
# rename interface if needed ENV{INTERFACE_NEW}=="?*", NAME="\$env{INTERFACE_NEW}"
LABEL="persistent_net_generator_end" EOF

  4. Ensure proper interface properties. For example: 

    hanamaster:# cd /etc/sysconfig/network/

hanamaster:# cat <<EOF >/etc/sysconfig/network/ifcfg-ethN 
BOOTPROTO='dhcp4'
MTU="9000" 
REMOTE_IPADDR=''
STARTMODE='onboot' 
LINK_REQUIRED=no 
LINK_READY_WAIT=5 
EOF

  5. Ensure that you can accommodate up to seven more Ethernet devices or network interaces, and restart wicked. For example: 

    hanamaster:# for dev in eth{1..7} ; do
ln -s -f ifcfg-ethN /etc/sysconfig/network/ifcfg-${dev} done

hanamaster:# systemctl restart wicked

  6. Create and attach a new network interface to the instance.

  7. Reboot.

  8. Modify /etc/iproute2/rt_tables.

    Important

    Repeat the following for each ENI that you attach to your instance.

    For example:

    hanamaster:# cd /etc/iproute2
hanamaster:/etc/iproute2 # echo "2 eth1_rt" >> rt_tables 
hanamaster:/etc/iproute2 # ip route add default via 172.16.1.122 dev eth1 table eth1_rt

hanamaster:/etc/iproute2 # ip rule 
0:	from all lookup local 
32766:	from all lookup main 
32767:	from all lookup default

hanamaster:/etc/iproute2 # ip rule add from <ENI IP Address> 
lookup eth1_rt prio 1000

hanamaster:/etc/iproute2 # ip rule 0:	from all lookup local
1000:	from <ENI IP address> lookup eth1_rt 
32766:	from all lookup main
32767:	from all lookup default