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, 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 # # # # 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.


    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 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