Home > Articles > Operating Systems, Server > Linux/UNIX/Open Source

  • Print
  • + Share This
This chapter is from the book

This chapter is from the book

Ethernet Bonding

As you develop fault-tolerant systems, you quickly realize that after disk failures, network issues are probably the second area that requires redundancy. After all, switches need maintenance from time to time and they do fail, as do networking cards and even Ethernet cables. If you want to be able to survive switch failure or maintenance, you need a system with multiple Ethernet ports connected to redundant switches. Most servers these days come with at least two Ethernet ports if not more, so it makes sense to set up Ethernet bonding, especially when you see how easy it is.

Ethernet bonding is a feature built into the Linux kernel as a module. With Ethernet bonding you can have multiple Ethernet ports that answer to the same IP address. Depending on the bonding mode you choose, you could have an active/passive scenario where one port activates only if the other appears off-line, or you could have an active/active scenario where you accept traffic across all ports.

Full documentation of all of the Ethernet bonding modes is available in the Documentation/networking/bonding.txt file included with any Linux kernel source. Below is an excerpt from that documentation that describes each bond mode:

    balance-rr or 0

    Round-robin policy: Transmit packets in sequential order from the first available slave through the last. This mode provides load balancing and fault tolerance.

    active-backup or 1

    Active-backup policy: Only one slave in the bond is active. A different slave becomes active if, and only if, the active slave fails. The bond’s MAC address is externally visible on only one port (network adapter) to avoid confusing the switch.

    balance-xor or 2

    XOR policy: Transmit based on the selected transmit hash policy. The default policy is a simple [(source MAC address XOR’d with destination MAC address) modulo slave count]. Alternate transmit policies may be selected via the xmit_hash_policy option, described below. This mode provides load balancing and fault tolerance.

    broadcast or 3

    Broadcast policy: transmits everything on all slave interfaces. This mode provides fault tolerance.

    802.3ad or 4

    IEEE 802.3ad Dynamic link aggregation. Creates aggregation groups that share the same speed and duplex settings. Utilizes all slaves in the active aggregator according to the 802.3ad specification.

    balance-tlb or 5

    Adaptive transmit load balancing: channel bonding that does not require any special switch support. The outgoing traffic is distributed according to the current load (computed relative to the speed) on each slave. Incoming traffic is received by the current slave. If the receiving slave fails, another slave takes over the MAC address of the failed receiving slave.

    balance-alb or 6

    Adaptive load balancing: includes balance-tlb plus receive load balancing (rlb) for IPV4 traffic, and does not require any special switch support. The receive load balancing is achieved by ARP negotiation. The bonding driver intercepts the ARP Replies sent by the local system on their way out and overwrites the source hardware address with the unique hardware address of one of the slaves in the bond such that different peers use different hardware addresses for the server.

So which bonding mode should you use? This can be a difficult question to answer as different networks support certain modes better than others. My recommendation is to try out some of the different bonding modes and test their fail-over by unplugging a cable while pinging the server. Different modes handle port failure differently, especially in the case where a cable is reconnected (or a switch is rebooted) and the port takes 30 seconds or so to come up. On some bonding modes pings will continue with no interruption, while on others you might have a 30-second outage while the port comes up. Note that because the bonding mode is set in the bonding module when it is loaded, if you change the bonding mode you will likely need to reboot (or at least take down the bond0 interface and unload and reload the module). For this example I will choose bonding mode 1 since it has only one port active at a time, so it is relatively safe on any switch.

The first step to configure bonding is to install the ifenslave package:

$ sudo apt-get install ifenslave

This package includes the ifenslave utility which the system will use to bond two interfaces together. The next step is to open /etc/modprobe.d/ aliases, scroll to the bottom of the file, and add

alias bond0 bonding
options bonding mode=1 miimon=100

The options line is what you can use to change your bonding mode. The miimon option tells the kernel how often to check the link state of the interface in milliseconds. In this case it is checked every 100 milliseconds.

The next step is to open your /etc/network/interfaces file and comment out any configuration lines for the network interfaces you will bond (you will probably have a configuration only for eth0). Also, if you have any references to auto eth0, comment those out as well. Then create a new configuration for the bond0 interface that mimics the settings you had for eth0. At the very end of the bond0 configuration you add an extra line called slaves that lists the different interfaces you want to bond together. Here’s an example interfaces file for my server:

# This file describes the network interfaces available on your system
# and how to activate them. For more information, see interfaces(5).

# The loopback network interface
auto lo
iface lo inet loopback

# The primary network interface
#auto eth0
#iface eth0 inet static
#    address 192.168.0.5
#    netmask 255.255.255.0
#    gateway 192.168.0.1

auto bond0
iface bond0 inet static
     address 192.168.0.5
     netmask 255.255.255.0
     gateway 192.168.0.1
     slaves eth0 eth1

Save your changes and then run sudo service networking restart or sudo /etc/init.d/networking restart. Once you run ifconfig, you should see the new bond0 device:

$ sudo ifconfig
bond0     Link encap:Ethernet  HWaddr 00:0c:29:28:13:3b  
          inet addr:192.168.0.5  Bcast:192.168.0.255
		    Mask:255.255.255.0
          inet6 addr: fe80::20c:29ff:fe28:133b/64 Scope:Link
          UP BROADCAST RUNNING MASTER MULTICAST  MTU:1500  Metric:1
          RX packets:38 errors:0 dropped:0 overruns:0 frame:0
          TX packets:43 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0 
          RX bytes:16644 (16.2 KB)  TX bytes:3282 (3.2 KB)

eth0      Link encap:Ethernet  HWaddr 00:0c:29:28:13:3b  
          UP BROADCAST RUNNING SLAVE MULTICAST  MTU:1500  Metric:1
          RX packets:37 errors:0 dropped:0 overruns:0 frame:0
          TX packets:43 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:16584 (16.1 KB)  TX bytes:3282 (3.2 KB)
          Interrupt:17 Base address:0x1400 

eth1      Link encap:Ethernet  HWaddr 00:0c:29:28:13:3b  
          UP BROADCAST RUNNING SLAVE MULTICAST  MTU:1500  Metric:1
          RX packets:1 errors:0 dropped:0 overruns:0 frame:0
          TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:60 (60.0 B)  TX bytes:0 (0.0 B)
          Interrupt:18 Base address:0x1480 

lo        Link encap:Local Loopback  
          inet addr:127.0.0.1  Mask:255.0.0.0
          inet6 addr: ::1/128 Scope:Host
          UP LOOPBACK RUNNING  MTU:16436  Metric:1
          RX packets:0 errors:0 dropped:0 overruns:0 frame:0
          TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0 
          RX bytes:0 (0.0 B)  TX bytes:0 (0.0 B)

Now you can test fail-over by unplugging eth0 while pinging the IP. Whenever a particular interface is down, the kernel will log both to dmesg and to /var/log/syslog. Here’s an example log entry like one you would see if you unplugged eth0:

Feb 14 16:43:28 kickseed kernel: [ 2901.700054] eth0: link down
Feb 14 16:43:29 kickseed kernel: [ 2901.731190] bonding: bond0:
    link status definitely down for interface eth0, disabling it
Feb 14 16:43:29 kickseed kernel: [ 2901.731300] bonding: bond0:
    making interface eth1 the new active one.
  • + Share This
  • 🔖 Save To Your Account

InformIT Promotional Mailings & Special Offers

I would like to receive exclusive offers and hear about products from InformIT and its family of brands. I can unsubscribe at any time.

Overview


Pearson Education, Inc., 221 River Street, Hoboken, New Jersey 07030, (Pearson) presents this site to provide information about products and services that can be purchased through this site.

This privacy notice provides an overview of our commitment to privacy and describes how we collect, protect, use and share personal information collected through this site. Please note that other Pearson websites and online products and services have their own separate privacy policies.

Collection and Use of Information


To conduct business and deliver products and services, Pearson collects and uses personal information in several ways in connection with this site, including:

Questions and Inquiries

For inquiries and questions, we collect the inquiry or question, together with name, contact details (email address, phone number and mailing address) and any other additional information voluntarily submitted to us through a Contact Us form or an email. We use this information to address the inquiry and respond to the question.

Online Store

For orders and purchases placed through our online store on this site, we collect order details, name, institution name and address (if applicable), email address, phone number, shipping and billing addresses, credit/debit card information, shipping options and any instructions. We use this information to complete transactions, fulfill orders, communicate with individuals placing orders or visiting the online store, and for related purposes.

Surveys

Pearson may offer opportunities to provide feedback or participate in surveys, including surveys evaluating Pearson products, services or sites. Participation is voluntary. Pearson collects information requested in the survey questions and uses the information to evaluate, support, maintain and improve products, services or sites, develop new products and services, conduct educational research and for other purposes specified in the survey.

Contests and Drawings

Occasionally, we may sponsor a contest or drawing. Participation is optional. Pearson collects name, contact information and other information specified on the entry form for the contest or drawing to conduct the contest or drawing. Pearson may collect additional personal information from the winners of a contest or drawing in order to award the prize and for tax reporting purposes, as required by law.

Newsletters

If you have elected to receive email newsletters or promotional mailings and special offers but want to unsubscribe, simply email information@informit.com.

Service Announcements

On rare occasions it is necessary to send out a strictly service related announcement. For instance, if our service is temporarily suspended for maintenance we might send users an email. Generally, users may not opt-out of these communications, though they can deactivate their account information. However, these communications are not promotional in nature.

Customer Service

We communicate with users on a regular basis to provide requested services and in regard to issues relating to their account we reply via email or phone in accordance with the users' wishes when a user submits their information through our Contact Us form.

Other Collection and Use of Information


Application and System Logs

Pearson automatically collects log data to help ensure the delivery, availability and security of this site. Log data may include technical information about how a user or visitor connected to this site, such as browser type, type of computer/device, operating system, internet service provider and IP address. We use this information for support purposes and to monitor the health of the site, identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents and appropriately scale computing resources.

Web Analytics

Pearson may use third party web trend analytical services, including Google Analytics, to collect visitor information, such as IP addresses, browser types, referring pages, pages visited and time spent on a particular site. While these analytical services collect and report information on an anonymous basis, they may use cookies to gather web trend information. The information gathered may enable Pearson (but not the third party web trend services) to link information with application and system log data. Pearson uses this information for system administration and to identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents, appropriately scale computing resources and otherwise support and deliver this site and its services.

Cookies and Related Technologies

This site uses cookies and similar technologies to personalize content, measure traffic patterns, control security, track use and access of information on this site, and provide interest-based messages and advertising. Users can manage and block the use of cookies through their browser. Disabling or blocking certain cookies may limit the functionality of this site.

Do Not Track

This site currently does not respond to Do Not Track signals.

Security


Pearson uses appropriate physical, administrative and technical security measures to protect personal information from unauthorized access, use and disclosure.

Children


This site is not directed to children under the age of 13.

Marketing


Pearson may send or direct marketing communications to users, provided that

  • Pearson will not use personal information collected or processed as a K-12 school service provider for the purpose of directed or targeted advertising.
  • Such marketing is consistent with applicable law and Pearson's legal obligations.
  • Pearson will not knowingly direct or send marketing communications to an individual who has expressed a preference not to receive marketing.
  • Where required by applicable law, express or implied consent to marketing exists and has not been withdrawn.

Pearson may provide personal information to a third party service provider on a restricted basis to provide marketing solely on behalf of Pearson or an affiliate or customer for whom Pearson is a service provider. Marketing preferences may be changed at any time.

Correcting/Updating Personal Information


If a user's personally identifiable information changes (such as your postal address or email address), we provide a way to correct or update that user's personal data provided to us. This can be done on the Account page. If a user no longer desires our service and desires to delete his or her account, please contact us at customer-service@informit.com and we will process the deletion of a user's account.

Choice/Opt-out


Users can always make an informed choice as to whether they should proceed with certain services offered by InformIT. If you choose to remove yourself from our mailing list(s) simply visit the following page and uncheck any communication you no longer want to receive: www.informit.com/u.aspx.

Sale of Personal Information


Pearson does not rent or sell personal information in exchange for any payment of money.

While Pearson does not sell personal information, as defined in Nevada law, Nevada residents may email a request for no sale of their personal information to NevadaDesignatedRequest@pearson.com.

Supplemental Privacy Statement for California Residents


California residents should read our Supplemental privacy statement for California residents in conjunction with this Privacy Notice. The Supplemental privacy statement for California residents explains Pearson's commitment to comply with California law and applies to personal information of California residents collected in connection with this site and the Services.

Sharing and Disclosure


Pearson may disclose personal information, as follows:

  • As required by law.
  • With the consent of the individual (or their parent, if the individual is a minor)
  • In response to a subpoena, court order or legal process, to the extent permitted or required by law
  • To protect the security and safety of individuals, data, assets and systems, consistent with applicable law
  • In connection the sale, joint venture or other transfer of some or all of its company or assets, subject to the provisions of this Privacy Notice
  • To investigate or address actual or suspected fraud or other illegal activities
  • To exercise its legal rights, including enforcement of the Terms of Use for this site or another contract
  • To affiliated Pearson companies and other companies and organizations who perform work for Pearson and are obligated to protect the privacy of personal information consistent with this Privacy Notice
  • To a school, organization, company or government agency, where Pearson collects or processes the personal information in a school setting or on behalf of such organization, company or government agency.

Links


This web site contains links to other sites. Please be aware that we are not responsible for the privacy practices of such other sites. We encourage our users to be aware when they leave our site and to read the privacy statements of each and every web site that collects Personal Information. This privacy statement applies solely to information collected by this web site.

Requests and Contact


Please contact us about this Privacy Notice or if you have any requests or questions relating to the privacy of your personal information.

Changes to this Privacy Notice


We may revise this Privacy Notice through an updated posting. We will identify the effective date of the revision in the posting. Often, updates are made to provide greater clarity or to comply with changes in regulatory requirements. If the updates involve material changes to the collection, protection, use or disclosure of Personal Information, Pearson will provide notice of the change through a conspicuous notice on this site or other appropriate way. Continued use of the site after the effective date of a posted revision evidences acceptance. Please contact us if you have questions or concerns about the Privacy Notice or any objection to any revisions.

Last Update: November 17, 2020