Router Installation and Configuration Manual/Configuring Bonder for Load Balancing and Aggregation

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This chapter describes how to configure the ImageStream router to use SAND's Bonder commands to load balance traffic across multiple circuits by aggregating multiple WAN devices. The Bonder commands are used to add aggregated devices on an interface-by-interface basis and to create the Bonder interface in the main WAN interface configuration file.
This chapter includes the following topics:
  • Configuring Load Balancing and Aggregation using Bonder
  • Valid interfaces for the bond command
Before configuring Bonder devices, you must configure your WAN interfaces and make the appropriate cabling connection for your needs. Refer to the hardware installation guide for your ImageStream product for information on making the WAN connection. See the Command Reference for more detailed command descriptions and instructions.
After logging in, the main menu is displayed (your menu may look slightly different):
ISis-Router main menu 
1. Configuration menu 
2. Show interface status 
3. Advanced 
4. Router software management 
5. Backup/Restore 
6. halt/reboot 
0. Log off 
Select menu option 1, Configuration menu, and press Enter to configure the router. The Configuration menu should appear (your menu may look slightly different):
Configuration menu 
1. AAA (Password) Configuration 
2. Global configuration 
3. Network interface configuration 
4. Firewall and QOS configuration 
5. Service configuration 
6. Dynamic routing configuration 
7. Save configuration to flash 
0. ISis-Router main menu 
From the "Configuration menu", select menu option 3, Network interface configuration, and press Enter. This will open the ImageStream router's primary configuration file, wan.conf in the default editor. The wan.conf file is also accessible from the command line in the /usr/local/sand directory.

Configuring Load Balancing and Aggregation Using Bonder

The Bonder interface for SAND devices allows multiple interfaces or subinterfaces to be treated as a single logical interface. A Bonder device is a standard network device and may be configured in the same manner as all physical devices and subinterfaces. This link aggregation/load balancing software is compatible with most similar tools on other manufacturer's routers. To use the bonder, all of the serial devices that you want to aggregate must have the same endpoint.
A Bonder device can:
  • aggregate multiple physical devices into a single logical device
  • aggregate physical devices of different speeds (i.e. T1 and DS3)
  • aggregate frame relay and ATM subinterfaces
  • aggregate subinterfaces with physical devices (i.e. 256K ATM VC and T1)
  • provide automatic, zero-downtime failover for multiple WAN devices interoperate with a Cisco router running per-packet CEF
Aggregated links are controlled by a virtual Bonder interface configured in the interface configuration file. The interface is configured similarly to a Serial WAN interface. For this example, we will use this configuration showing a point-to-point T1 and a frame relay PVC:
interface Serial0 
description Leased line to Mexico City 
encapsulation hdlc 
ip address
interface Serial1 
encapsulation frame-relay ietf 
bandwidth 1536000 
frame-relay lmi-type ansi 
frame-relay interval 10 
interface Serial1.1 
description Frame to Mexico City 
encapsulation frame-relay ietf 
frame-relay interface-dlci 16 
ip address 
In the example below, we will bond Serial0 and Serial1.1 together. For the link aggregation to function, both Serial0 and Serial1.1 must terminate on the same remote router. The syntax of the Bonder interface command is:
     interface Bonder XX
where XX is a device number. The location of a Bonder interface declaration in the interface configuration file is not important. By convention, the first Bonder device is Bonder0, though you may assign any number. You do not need to specify an encapsulation type or bandwidth, as both will be ignored. You must specify an ip address. A description field is optional. To connect the Serial interfaces to the Bonder device that you have created, use the bond keyword. The syntax of the bond keyword is:
     bond Device Name 
In the example below, we have bonded the two Serial devices from above:
     interface Bonder0 
     description Bonded T1s to Mexico City 
     bond Serial0 
     bond Serial1.1 
     ip address 
The Bonder interface appears as a regular interface in the router, meaning you can make modifications to the Bonder device configuration without taking down other interfaces. You can use firewalling, bandwidth limiting, rule-based routing and other advanced features of the router with any Bonder device you create. Like other interfaces, the Bonder device is also available via SNMP for monitoring purposes.
The IP addresses on the individual T1s added to the bonded device using the bond keyword can be set to any valid IP address, and do not necessarily need to be identical. In the example above, both Serial interfaces used the same IP address. If you choose to use the same IP address on all of the bonded interfaces, you must use a host netmask (/32 or on the individual serial devices.
Bonder distributes the load evenly based on each interface's bandwidth and the number of packets currently queued to that particular device. For example, a DS3 link bonded with a T1 line will send more traffic to the DS3 and will efficiently use the available bandwidth on both interfaces. Bonder automatically calculates bandwidth based on the active bonded interfaces and will not attempt to use any interface which has hardware or protocol down.

Valid Interfaces for the Bond Command

The bond command can only be used in conjunction with a Bonder device. You may only bond SAND interfaces. You cannot bond the following:
  • Ethernet interfaces
  • Token ring interfaces
  • Tunnel interfaces
  • VPN interfaces
  • VLAN interfaces
Note: You must save the settings to the router's non-volatile flash memory! If the router is rebooted before saving, your changes will be lost! See Chapter 26, "Backup/Restore Menu: Managing Configurations" for more information.
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