Configuring GLBP
Gateway Load Balancing Protocol (GLBP) protects data traffic from a failed device or circuit, like Hot Standby Router Protocol (HSRP) and Virtual Router Redundancy Protocol (VRRP), while allowing packet load sharing between a group of redundant devices.
Finding Feature Information
Your software release may not support all the features documented in this module. For the latest caveats and feature information, see Bug Search Tool and the release notes for your platform and software release. To find information about the features documented in this module, and to see a list of the releases in which each feature is supported, see the feature information table at the end of this module.
Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to http://www.cisco.com/go/cfn. An account on Cisco.com is not required.
Restrictions for GLBP
Enhanced Object Tracking (EOT) is not stateful switchover (SSO)-aware and cannot be used with GLBP in SSO mode.
Prerequisites for GLBP
Before configuring GLBP, ensure that the devices can support multiple MAC addresses on the physical interfaces. For each GLBP forwarder to be configured, an additional MAC address is used.
Information About GLBP
GLBP Overview
GLBP provides automatic device backup for IP hosts configured with a single default gateway on an IEEE 802.3 LAN. Multiple first-hop devices on the LAN combine to offer a single virtual first-hop IP device while sharing the IP packet forwarding load. Other devices on the LAN act as redundant GLBP devices that will become active if any of the existing forwarding devices fail.
GLBP performs a similar function for the user as HSRP and VRRP. HSRP and VRRP allow multiple devices to participate in a virtual device group configured with a virtual IP address. One member is elected to be the active device to forward packets sent to the virtual IP address for the group. The other devices in the group are redundant until the active device fails. These standby devices have unused bandwidth that the protocol is not using. Although multiple virtual device groups can be configured for the same set of devices, the hosts must be configured for different default gateways, which results in an extra administrative burden. The advantage of GLBP is that it additionally provides load balancing over multiple devices (gateways) using a single virtual IP address and multiple virtual MAC addresses. The forwarding load is shared among all devices in a GLBP group rather than being handled by a single device while the other devices stand idle. Each host is configured with the same virtual IP address, and all devices in the virtual device group participate in forwarding packets. GLBP members communicate between each other through hello messages sent every 3 seconds to the multicast address 224.0.0.102, UDP port 3222 (source and destination).
GLBP Packet Types
GLBP uses 3 different packet types to operate. The packet types are Hello, Request, and Reply. The Hello packet is used to advertise protocol information. Hello packets are multicast, and are sent when any virtual gateway or virtual forwarder is in Speak, Standby or Active state. Request and Reply packets are used for virtual MAC assignment. They are both unicast messages to and from the active virtual gateway (AVG).
GLBP Active Virtual Gateway
Members of a GLBP group elect one gateway to be the active virtual gateway (AVG) for that group. Other group members provide backup for the AVG if the AVG becomes unavailable. The AVG assigns a virtual MAC address to each member of the GLBP group. Each gateway assumes responsibility for forwarding packets sent to the virtual MAC address assigned to it by the AVG. These gateways are known as active virtual forwarders (AVFs) for their virtual MAC address.
The AVG is also responsible for answering Address Resolution Protocol(ARP) requests for the virtual IP address. Load sharing is achieved by the AVG replying to the ARP requests with different virtual MAC addresses.
When the no glbp load-balancing command is configured, if the AVG does not have an AVF, it preferentially responds to ARP requests with the MAC address of the first listening virtual forwarder (VF), which will causes traffic to route via another gateway until that VF migrates back to being the current AVG.
In the figure below, Router A (or Device A) is the AVG for a GLBP group, and is responsible for the virtual IP address 10.21.8.10. Router A is also an AVF for the virtual MAC address 0007.b400.0101. Router B (or Device B) is a member of the same GLBP group and is designated as the AVF for the virtual MAC address 0007.b400.0102. Client 1 has a default gateway IP address of 10.21.8.10 and a gateway MAC address of 0007.b400.0101. Client 2 shares the same default gateway IP address but receives the gateway MAC address 0007.b400.0102 because Router B is sharing the traffic load with Router A.
If Router A becomes unavailable, Client 1 will not lose access to the WAN because Router B will assume responsibility for forwarding packets sent to the virtual MAC address of Router A, and for responding to packets sent to its own virtual MAC address. Router B will also assume the role of the AVG for the entire GLBP group. Communication for the GLBP members continues despite the failure of a device in the GLBP group.
GLBP Virtual MAC Address Assignment
A GLBP group allows up to four virtual MAC addresses per group. The AVG is responsible for assigning the virtual MAC addresses to each member of the group. Other group members request a virtual MAC address after they discover the AVG through hello messages. Gateways are assigned the next MAC address in sequence. A virtual forwarder that is assigned a virtual MAC address by the AVG is known as a primary virtual forwarder. Other members of the GLBP group learn the virtual MAC addresses from hello messages. A virtual forwarder that has learned the virtual MAC address is referred to as a secondary virtual forwarder.
GLBP Virtual Gateway Redundancy
GLBP operates virtual gateway redundancy in the same way as HSRP. One gateway is elected as the AVG, another gateway is elected as the standby virtual gateway, and the remaining gateways are placed in a listen state.
If an AVG fails, the standby virtual gateway will assume responsibility for the virtual IP address. A new standby virtual gateway is then elected from the gateways in the listen state.
GLBP Virtual Forwarder Redundancy
Virtual forwarder redundancy is similar to virtual gateway redundancy with an AVF. If the AVF fails, one of the secondary virtual forwarders in the listen state assumes responsibility for the virtual MAC address.
The new AVF is also a primary virtual forwarder for a different forwarder number. GLBP migrates hosts away from the old forwarder number using two timers that start as soon as the gateway changes to the active virtual forwarder state. GLBP uses the hello messages to communicate the current state of the timers.
The redirect time is the interval during which the AVG continues to redirect hosts to the old virtual forwarder MAC address. When the redirect time expires, the AVG stops using the old virtual forwarder MAC address in ARP replies, although the virtual forwarder will continue to forward packets that were sent to the old virtual forwarder MAC address.
The secondary holdtime is the interval during which the virtual forwarder is valid. When the secondary holdtime expires, the virtual forwarder is removed from all gateways in the GLBP group. The expired virtual forwarder number becomes eligible for reassignment by the AVG.
GLBP Gateway Priority
GLBP gateway priority determines the role that each GLBP gateway plays and what happens if the AVG fails.
Priority also determines if a GLBP device functions as a backup virtual gateway and the order of ascendancy to becoming an AVG if the current AVG fails. You can configure the priority of each backup virtual gateway with a value of 1 through 255 using the glbp priority command.
In the "GLBP Topology" figure, if Router A (or Device A)—the AVG in a LAN topology—fails, an election process takes place to determine which backup virtual gateway should take over. In this example, Router B (or Device B) is the only other member in the group so it will automatically become the new AVG. If another device existed in the same GLBP group with a higher priority, then the device with the higher priority would be elected. If both devices have the same priority, the backup virtual gateway with the higher IP address would be elected to become the active virtual gateway.
By default, the GLBP virtual gateway preemptive scheme is disabled. A backup virtual gateway can become the AVG only if the current AVG fails, regardless of the priorities assigned to the virtual gateways. You can enable the GLBP virtual gateway preemptive scheme using the glbp preempt command. Preemption allows a backup virtual gateway to become the AVG, if the backup virtual gateway is assigned a higher priority than the current AVG.
GLBP Gateway Weighting and Tracking
GLBP uses a weighting scheme to determine the forwarding capacity of each device in the GLBP group. The weighting assigned to a device in the GLBP group can be used to determine whether it will forward packets and, if so, the proportion of hosts in the LAN for which it will forward packets. Thresholds can be set to disable forwarding when the weighting for a GLBP group falls below a certain value, and when it rises above another threshold, forwarding is automatically reenabled.
The GLBP group weighting can be automatically adjusted by tracking the state of an interface within the device. If a tracked interface goes down, the GLBP group weighting is reduced by a specified value. Different interfaces can be tracked to decrement the GLBP weighting by varying amounts.
By default, the GLBP virtual forwarder preemptive scheme is enabled with a delay of 30 seconds. A backup virtual forwarder can become the AVF if the current AVF weighting falls below the low weighting threshold for 30 seconds. You can disable the GLBP forwarder preemptive scheme using the no glbp forwarder preempt command or change the delay using the glbp forwarder preempt delay minimum command.
GLBP MD5 Authentication
GLBP MD5 authentication uses the industry-standard MD5 algorithm for improved reliability and security. MD5 authentication provides greater security than the alternative plain text authentication scheme and protects against spoofing software.
MD5 authentication allows each GLBP group member to use a secret key to generate a keyed MD5 hash that is part of the outgoing packet. A keyed hash of an incoming packet is generated and, if the hash within the incoming packet does not match the generated hash, the packet is ignored.
The key for the MD5 hash can either be given directly in the configuration using a key string or supplied indirectly through a key chain. The key string cannot exceed 100 characters in length.
A device will ignore incoming GLBP packets from devices that do not have the same authentication configuration for a GLBP group. GLBP has three authentication schemes:
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No authentication
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Plain text authentication
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MD5 authentication
GLBP packets will be rejected in any of the following cases:
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The authentication schemes differ on the device and in the incoming packet.
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MD5 digests differ on the device and in the incoming packet.
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Text authentication strings differ on the device and in the incoming packet.
GLBP Benefits
Load Sharing
You can configure GLBP in such a way that traffic from LAN clients can be shared by multiple devices, thereby sharing the traffic load more equitably among available devices.
Multiple Virtual Devices
GLBP supports up to 1024 virtual devices (GLBP groups) on each physical interface of a device and up to four virtual forwarders per group.
Preemption
The redundancy scheme of GLBP enables you to preempt an active virtual gateway (AVG) with a higher priority backup virtual gateway that has become available. Forwarder preemption works in a similar way, except that forwarder preemption uses weighting instead of priority and is enabled by default.
Authentication
GLBP supports the industry-standard message digest 5 (MD5) algorithm for improved reliability, security, and protection against GLBP-spoofing software. A device within a GLBP group with a different authentication string than other devices will be ignored by other group members. You can alternatively use a simple text password authentication scheme between GLBP group members to detect configuration errors.
How to Configure GLBP
Customizing GLBP
Customizing the behavior of GLBP is optional. Be aware that as soon as you enable a GLBP group, that group is operating. It is possible that if you first enable a GLBP group before customizing GLBP, the device could take over control of the group and become the AVG before you have finished customizing the feature. Therefore, if you plan to customize GLBP, it is a good idea to do so before enabling GLBP.
Procedure
Command or Action | Purpose | |||
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Step 1 |
enable Example:
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Enables privileged EXEC mode.
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Step 2 |
configure terminal Example:
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Enters global configuration mode. |
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Step 3 |
interface type number Example:
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Specifies an interface type and number, and enters interface configuration mode. |
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Step 4 |
ip address ip-address mask [secondary] Example:
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Specifies a primary or secondary IP address for an interface. |
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Step 5 |
glbp group timers [msec] hellotime [msec] holdtime Example:
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Configures the interval between successive hello packets sent by the AVG in a GLBP group.
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Step 6 |
glbp group timers redirect redirect timeout Example:
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Configures the time interval during which the AVG continues to redirect clients to an AVF. The default is 600 seconds (10 minutes).
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Step 7 |
glbp group load-balancing [host-dependent | round-robin | weighted] Example:
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Specifies the method of load balancing used by the GLBP AVG. |
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Step 8 |
glbp group priority level Example:
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Sets the priority level of the gateway within a GLBP group.
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Step 9 |
glbp group preempt [delay minimum seconds] Example:
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Configures the device to take over as AVG for a GLBP group if it has a higher priority than the current AVG.
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Step 10 |
glbp group name redundancy-name Example:
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Enables IP redundancy by assigning a name to the GLBP group.
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Step 11 |
exit Example:
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Exits interface configuration mode, and returns the device to global configuration mode. |
Configuring GLBP MD5 Authentication Using a Key String
Procedure
Command or Action | Purpose | |
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Step 1 |
enable Example:
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Enables privileged EXEC mode.
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Step 2 |
configure terminal Example:
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Enters global configuration mode. |
Step 3 |
interface type number Example:
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Configures an interface type and enters interface configuration mode. |
Step 4 |
ip address ip-address mask [secondary] Example:
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Specifies a primary or secondary IP address for an interface. |
Step 5 |
glbp group-number authentication md5 key-string [ 0 | 7] key Example:
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Configures an authentication key for GLBP MD5 authentication.
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Step 6 |
glbp group-number ip [ip-address [secondary]] Example:
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Enables GLBP on an interface and identifies the primary IP address of the virtual gateway. |
Step 7 |
Repeat Steps 1 through 6 on each device that will communicate. |
— |
Step 8 |
end Example:
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Returns to privileged EXEC mode. |
Step 9 |
show glbp Example:
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(Optional) Displays GLBP information.
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Configuring GLBP MD5 Authentication Using a Key Chain
Perform this task to configure GLBP MD5 authentication using a key chain. Key chains allow a different key string to be used at different times according to the key chain configuration. GLBP will query the appropriate key chain to obtain the current live key and key ID for the specified key chain.
Procedure
Command or Action | Purpose | |
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Step 1 |
enable Example:
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Enables privileged EXEC mode.
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Step 2 |
configure terminal Example:
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Enters global configuration mode. |
Step 3 |
key chain name-of-chain Example:
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Enables authentication for routing protocols and identifies a group of authentication keys and enters key-chain configuration mode. |
Step 4 |
key key-id Example:
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Identifies an authentication key on a key chain.
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Step 5 |
key-string string Example:
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Specifies the authentication string for a key and enters key-chain key configuration mode.
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Step 6 |
exit Example:
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Returns to key-chain configuration mode. |
Step 7 |
exit Example:
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Returns to global configuration mode. |
Step 8 |
interface type number Example:
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Configures an interface type and enters interface configuration mode. |
Step 9 |
ip address ip-address mask [secondary] Example:
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Specifies a primary or secondary IP address for an interface. |
Step 10 |
glbp group-number authentication md5 key-chain name-of-chain Example:
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Configures an authentication MD5 key chain for GLBP MD5 authentication.
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Step 11 |
glbp group-number ip [ip-address [secondary]] Example:
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Enables GLBP on an interface and identifies the primary IP address of the virtual gateway. |
Step 12 |
Repeat Steps 1 through 10 on each device that will communicate. |
— |
Step 13 |
end Example:
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Returns to privileged EXEC mode. |
Step 14 |
show glbp Example:
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(Optional) Displays GLBP information.
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Step 15 |
show key chain Example:
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(Optional) Displays authentication key information. |
Configuring GLBP Text Authentication
Text authentication provides minimal security. Use MD5 authentication if security is required.
Procedure
Command or Action | Purpose | |
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Step 1 |
enable Example:
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Enables privileged EXEC mode.
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Step 2 |
configure terminal Example:
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Enters global configuration mode. |
Step 3 |
interface type number Example:
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Configures an interface type and enters interface configuration mode. |
Step 4 |
ip address ip-address mask [secondary] Example:
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Specifies a primary or secondary IP address for an interface. |
Step 5 |
glbp group-number authentication text string Example:
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Authenticates GLBP packets received from other devices in the group.
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Step 6 |
glbp group-number ip [ip-address [secondary]] Example:
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Enables GLBP on an interface and identifies the primary IP address of the virtual gateway. |
Step 7 |
Repeat Steps 1 through 6 on each device that will communicate. |
— |
Step 8 |
end Example:
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Returns to privileged EXEC mode. |
Step 9 |
show glbp Example:
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(Optional) Displays GLBP information.
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Configuring GLBP Weighting Values and Object Tracking
GLBP weighting is used to determine whether a GLBP group can act as a virtual forwarder. Initial weighting values can be set and optional thresholds specified. Interface states can be tracked and a decrement value set to reduce the weighting value if the interface goes down. When the GLBP group weighting drops below a specified value, the group will no longer be an active virtual forwarder. When the weighting rises above a specified value, the group can resume its role as an active virtual forwarder.
Procedure
Command or Action | Purpose | |
---|---|---|
Step 1 |
enable Example:
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Enables privileged EXEC mode.
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Step 2 |
configure terminal Example:
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Enters global configuration mode. |
Step 3 |
track object-number interface type number {line-protocol |{ip | ipv6} routing} Example:
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Configures an interface to be tracked where changes in the state of the interface affect the weighting of a GLBP gateway, and enters tracking configuration mode.
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Step 4 |
exit Example:
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Returns to global configuration mode. |
Step 5 |
interface type number Example:
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Enters interface configuration mode. |
Step 6 |
glbp group weighting maximum [lower lower] [upper upper] Example:
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Specifies the initial weighting value, and the upper and lower thresholds, for a GLBP gateway. |
Step 7 |
glbp group weighting track object-number [decrement value] Example:
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Specifies an object to be tracked that affects the weighting of a GLBP gateway.
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Step 8 |
glbp group forwarder preempt [delay minimum seconds] Example:
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Configures the device to take over as AVF for a GLBP group if the current AVF for a GLBP group falls below its low weighting threshold.
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Step 9 |
exit Example:
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Returns to privileged EXEC mode. |
Step 10 |
show track [object-number | brief] [interface [brief] | ip route [ brief] | resolution | timers] Example:
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Displays tracking information. |
Troubleshooting GLBP
GLBP introduces five privileged EXEC mode commands to enable display of diagnostic output concerning various events relating to the operation of GLBP. The debug condition glbp ,debug glbp errors , debug glbp events , debug glbp packets , and debug glbp terse commands are intended only for troubleshooting purposes because the volume of output generated by the software can result in severe performance degradation on the device. Perform this task to minimize the impact of using the debug glbp commands.
This procedure will minimize the load on the device created by the debug condition glbp or debug glbp command because the console port is no longer generating character-by-character processor interrupts. If you cannot connect to a console directly, you can run this procedure via a terminal server. If you must break the Telnet connection, however, you may not be able to reconnect because the device may be unable to respond due to the processor load of generating the debugging output.
Before you begin
This task requires a device running GLBP to be attached directly to a console.
Procedure
Command or Action | Purpose | |
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Step 1 |
enable Example:
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Enables privileged EXEC mode.
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Step 2 |
configure terminal Example:
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Enters global configuration mode. |
Step 3 |
no logging console Example:
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Disables all logging to the console terminal.
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Step 4 |
Use Telnet to access a device port and repeat Steps 1 and 2. |
Enters global configuration mode in a recursive Telnet session, which allows the output to be redirected away from the console port. |
Step 5 |
end Example:
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Exits to privileged EXEC mode. |
Step 6 |
terminal monitor Example:
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Enables logging output on the virtual terminal. |
Step 7 |
debug condition glbp interface-type interface-number group [forwarder] Example:
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Displays debugging messages about GLBP conditions.
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Step 8 |
terminal no monitor Example:
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Disables logging on the virtual terminal. |
Configuration Examples for GLBP
Example: Customizing GLBP Configuration
Device(config)# interface GigabitEthernet 1/0/1
Device(config-if)# ip address 10.21.8.32 255.255.255.0
Device(config-if)# glbp 10 timers 5 18
Device(config-if)# glbp 10 timers redirect 1800 28800
Device(config-if)# glbp 10 load-balancing host-dependent
Device(config-if)# glbp 10 priority 254
Device(config-if)# glbp 10 preempt delay minimum 60
Example: Configuring GLBP MD5 Authentication Using Key Strings
The following example shows how to configure GLBP MD5 authentication using a key string:
Device(config)# interface GigabitEthernet 1/0/1
Device(config-if)# ip address 10.0.0.1 255.255.255.0
Device(config-if)# glbp 2 authentication md5 key-string ThisStringIsTheSecretKey
Device(config-if)# glbp 2 ip 10.0.0.10
Example: Configuring GLBP MD5 Authentication Using Key Chains
In the following example, GLBP queries the key chain “AuthenticateGLBP” to obtain the current live key and key ID for the specified key chain:
Device(config)# key chain AuthenticateGLBP
Device(config-keychain)# key 1
Device(config-keychain-key)# key-string ThisIsASecretKey
Device(config-keychain-key)# exit
Device(config-keychain)# exit
Device(config)# interface GigabitEthernet 1/0/1
Device(config-if)# ip address 10.0.0.1 255.255.255.0
Device(config-if)# glbp 2 authentication md5 key-chain AuthenticateGLBP
Device(config-if)# glbp 2 ip 10.0.0.10
Example: Configuring GLBP Text Authentication
Device(config)# interface GigabitEthernet 0/0/0
Device(config-if)# ip address 10.21.8.32 255.255.255.0
Device(config-if)# glbp 10 authentication text stringxyz
Device(config-if)# glbp 10 ip 10.21.8.10
Example: Configuring GLBP Weighting
In the following example, the device is configured to track the IP routing state of the POS interface 5/0/0 and 6/0/0, an initial GLBP weighting with upper and lower thresholds is set, and a weighting decrement value of 10 is set. If POS interface 5/0/0 and 6/0/0 go down, the weighting value of the device is reduced.
Device(config)# track 1 interface GigabitEthernet 1/0/1 line-protocol
Device(config)# track 2 interface GigabitEthernet 1/0/3 line-protocol
Device(config)# interface TenGigabitEthernet 0/0/1
Device(config-if)# ip address 10.21.8.32 255.255.255.0
Device(config-if)# glbp 10 weighting 110 lower 95 upper 105
Device(config-if)# glbp 10 weighting track 1 decrement 10
Device(config-if)# glbp 10 weighting track 2 decrement 10
Example: Enabling GLBP Configuration
In the following example, the device is configured to enable GLBP, and the virtual IP address of 10.21.8.10 is specified for GLBP group 10:
Device(config)# interface GigabitEthernet 0/0/0
Device(config-if)# ip address 10.21.8.32 255.255.255.0
Device(config-if)# glbp 10 ip 10.21.8.10
Additional References for GLBP
Related Documents
Related Topic |
Document Title |
---|---|
GLBP commands: complete command syntax, command mode, command history, defaults, usage guidelines, and examples. |
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Key chains and key management commands: complete command syntax, command mode, command history, defaults, usage guidelines, and examples |
Cisco IOS IP Routing Protocol-Independent Command Reference |
Object tracking |
"Configuring Enhanced Object Tracking" module |
VRRP |
"Configuring VRRP" module |
HSRP |
"Configuring HSRP" module |
Technical Assistance
Description |
Link |
---|---|
The Cisco Support and Documentation website provides online resources to download documentation, software, and tools. Use these resources to install and configure the software and to troubleshoot and resolve technical issues with Cisco products and technologies. Access to most tools on the Cisco Support and Documentation website requires a Cisco.com user ID and password. |
Feature Information for GLBP
The following table provides release information about the feature or features described in this module. This table lists only the software release that introduced support for a given feature in a given software release train. Unless noted otherwise, subsequent releases of that software release train also support that feature.
Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to www.cisco.com/go/cfn. An account on Cisco.com is not required.
Feature Name |
Releases |
Feature Configuration Information |
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Gateway Load Balancing Protocol |
GLBP protects data traffic from a failed router or circuit, like HSRP and VRRP, while allowing packet load sharing between a group of redundant routers. In Cisco IOS Release Cisco IOS XE Release 3.6E, this feature is supported on the following platforms:
The following commands were introduced or modified by this feature: glbp forwarder preempt , glbp ip , glbp load-balancing , glbp name , glbp preempt , glbp priority , glbp timers , glbp timers redirect , glbp weighting , glbp weighting track , show glbp . |
|
GLBP MD5 Authentication |
Cisco IOS XE 3.6E |
MD5 authentication provides greater security than the alternative plain text authentication scheme. MD5 authentication allows each GLBP group member to use a secret key to generate a keyed MD5 hash that is part of the outgoing packet. A keyed hash of an incoming packet is generated and, if the hash within the incoming packet does not match the generated hash, the packet is ignored. In Cisco IOS Release Cisco IOS XE Release 3.6E, this feature is supported on the following platforms:
The following commands were modified by this feature: glbp authentication , show glbp . |
Glossary
active RP—The Route Processor (RP) controls the system, provides network services, runs routing protocols and presents the system management interface.
AVF—active virtual forwarder. One virtual forwarder within a GLBP group is elected as active virtual forwarder for a specified virtual MAC address, and it is responsible for forwarding packets sent to that MAC address. Multiple active virtual forwarders can exist for each GLBP group.
AVG—active virtual gateway. One virtual gateway within a GLBP group is elected as the active virtual gateway, and is responsible for the operation of the protocol.
GLBP gateway—Gateway Load Balancing Protocol gateway. A router or gateway running GLBP. Each GLBP gateway may participate in one or more GLBP groups.
GLBP group—Gateway Load Balancing Protocol group. One or more GLBP gateways configured with the same GLBP group number on connected Ethernet interfaces.
NSF—nonstop forwarding. The ability of a router to continue to forward traffic to a router that may be recovering from a failure. Also, the ability of a router recovering from a failure to continue to correctly forward traffic sent to it by a peer.
RP—Route Processor. A generic term for the centralized control unit in a chassis. Platforms usually use a platform-specific term, such as RSP on the Cisco 7500, the PRE on the Cisco 10000, or the SUP+MSFC on the Cisco 7600.
RPR—Route Processor Redundancy. RPR provides an alternative to the High System Availability (HSA) feature. HSA enables a system to reset and use a standby Route Processor (RP) if the active RP fails. Using RPR, you can reduce unplanned downtime because RPR enables a quicker switchover between an active and standby RP if the active RP experiences a fatal error.
RPR+—An enhancement to RPR in which the standby RP is fully initialized.
standby RP—An RP that has been fully initialized and is ready to assume control from the active RP should a manual or fault-induced switchover occur.
switchover—An event in which system control and routing protocol execution are transferred from the active RP to the standby RP. Switchover may be a manual operation or may be induced by a hardware or software fault. Switchover may include transfer of the packet forwarding function in systems that combine system control and packet forwarding in an indivisible unit.
vIP—virtual IP address. An IPv4 address. There must be only one virtual IP address for each configured GLBP group. The virtual IP address must be configured on at least one GLBP group member. Other GLBP group members can learn the virtual IP address from hello messages.