Cisco Gateway Load Balance Protocol (GLBP) Configuration Process and Commands

Arya MirNetworking and Communications

Oct 12, 2013 (3 years and 10 months ago)

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The configuration of Gateway Load Balancing Protocol (GLBP) is very similar to that of Hot Standby Router Protocol (HSRP) and Virtual Router Redundancy Protocol(VRRP), and like them is not overly complex to initially configure and use the default settings. This section will first go over the configuration process steps and commands that are used to perform a basic GLBP configuration. An example will then be shown on how these steps can be used to configure GLBP in a sample networking topology.

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Cisco Gateway Load Balance Protocol (GLBP)
Configuration Process and Commands
Date: Oct 9, 2013 By
Sean Wilkins
.
Article is provided courtesy of
Cisco Press
.
In this article, networking consultant Sean Wilkins takes the concepts covered in his
earlier "
Introduction to GLBP
" article and discusses how those concepts can be applied to
real devices.
The configuration of Gateway Load Balancing Protocol (GLBP) is very
similar to that of H
ot
Standby Router Protocol
(HSRP) and
Virtual Router
Redundancy Protocol
(VRRP),
and like
them is not overly complex to initially configure and use the default
settings. This section will
first go over the configuration process steps and
commands that are used to perform a basic
GLBP configuration. An example will
then be shown on how these steps can be used to
configure GLBP in a sample
networking topology.
GLBP Simple Configuration Steps
Like HSRP and VRRP, only a few commands are used to configure GLBP
using the default
settings. Table 1 shows the common commands that are used to
configure basic GLBP as
well a few of the most commonly used commands to alter
GLBP’s behavior.
Table 1
- VRRP Configuration Commands
1
Enter privileged EXEC mode
router>
enable
2
Enter global configuration
mode
router#
configure
terminal
3
Enter interface configuration
mode
router(config)#
interface
interface
4
Configure an IP address on
the interface
router(config-if)#
ip
address
address netmask
5
Configure an GLBP virtual IP
address
Notes:
The
group-number
can be
any value from 1 to 1023.
This address (if entered) must
be in the same subnet as the
interface IP address (primary
or secondary). It is possible
not to enter an
ip-address;
in
this case, the virtual IP
address is learned from
another GLBP device.
router(config-if)#
glbp
group-
number

ip [
ip-address
]
6
Configure the GLBP priority
router(config-if)#
glbp
group-
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6
Configure the GLBP priority
(optional)
Note: The valid values for the
priority
are from 1 through
255.
number

priority
priority
7
Configure GLBP preemption
(optional)
Note: GLBP preemption is
disabled by default.
router(config-if)#
glbp
group-
number

preempt
VRRP Simple Example
This section covers a simple example of how GLBP can be configured
in a basic common
topology. Figure 1 displays a common topology that exists in
many networks that would
potentially use a First Hop Redundancy Protocol (FHRP)
like HSRP, VRRP, or GLBP. In this
case, both R1 and R2 connect to a common
subnet where hosts reside; this is the same
interface used by GLBP to
communicate with the other GLBP devices.
Figure 1
GLBP example topology
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Tables 2 and 3 show the basic commands that are required to
configure GLBP between the
two devices shown in Figure 1.
The configuration will perform the following:
Configure the IP addresses 172.16.1.1/24 (R1)
and 172.16.2.1 (R2) on their Fa0/0
interfaces
Configure GLBP between R1 and R2 using the IP
addresses 10.10.10.1/24 (R1) and
10.10.10.2/24(R2) and a virtual IP address of
10.10.10.5 on their Fa1/0 interfaces
Table 2
- R1 Simple Example Configuration
1
Enter privileged EXEC mode.
R1>
enable
2
Enter global configuration
mode.
R1#
configure terminal
3
Enter interface configuration
mode.
R1(config)#
interface
fa0/0
4
Configure an IP address on
the interface.
R1(config-if)#
ip
address
172.16.1.1 255.255.255.0
5
Enter interface configuration
mode.
R1(config)#
interface
fa0/1
6
Configure an IP address on
the interface.
R1(config-if)#
ip
address
10.10.20.1 255.255.255.252
7
Enter interface configuration
mode.
R1(config)#
interface
fa1/0
8
Configure an IP address on
the interface.
R1(config-if)#
ip
address
10.10.10.1 255.255.255.0
9
Configure GLBP using a virtual
IP address of 10.10.10.5 using
group 1.
R1(config-if)#
glbp 1 ip
10.10.10.5
Table 3
- R2 Simple Example Configuration
1
Enter privileged EXEC mode.
R2>
enable
2
Enter global configuration
mode.
R2#
configure terminal
3
Enter interface configuration
mode.
R2(config)#
interface
fa0/0
4
Configure an IP address on
the interface.
R2(config-if)#
ip
address
172.16.2.1 255.255.255.0
5
Enter interface configuration
mode.
R2(config)#
interface
fa0/1
6
Configure an IP address on
the interface.
R2(config-if)#
ip
address
10.10.20.2 255.255.255.252
7
Enter interface configuration
mode.
R2(config)#
interface
fa1/0
8
Configure an IP address on
the interface.
R2(config-if)#
ip
address
10.10.10.2 255.255.255.0
9
Configure GLBP using a virtual
R2(config-if)#
glbp 1 ip
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9
Configure GLBP using a virtual
IP address of 10.10.10.5 using
group 1.
10.10.10.5
GLBP Complex Configuration Steps
In this section, the commands that are covered will extend to those
that modify the default
behavior of the GLBP process. These include GLBP timers
(
hello
,
hold
,
redirect
and
timeout
), altering the
default load balancing behavior (the default is
round robin
),
configuring GLBP authentication, and basic interface tracking. Table 4 covers
all the
commands that are required to perform these steps.
Table 4
- GLBP Complex Configuration Commands
1
Configure the GLBP
hello
and
hold
timers.
router(config-if)#
glbp
group-
number
timers
[
msec
]
hello-
timer
[
msec
]
hold-timer
2
Configure the GLBP redirect
timers.
Note: The
redirect-timer
is the
amount of time that passes
before the AVG assumes that
the
forwarder is not going to
return; the
timeout
is the
amount of time until the virtual
MAC address that was used by
the
failed AVF is no longer
functional.
router(config-if)#
glbp
group-
number
timers redirect
redirect-timer
timeout



1
Configure the GLBP load
balancing behavior.
router(config-if)#
glbp
group-
number
load-balancing
[
host-
dependent
|
round-robin
|
weighted
]



1
Configure GLBP Authentication.
router(config-if)#
glbp
group-
number
authentication
{
text
plain-text-string
|
md5
{
key-
string
keystring
|
key-chain
key-chain-name
}}

If a
key-chain
is configured with
the command above,
follow
these next few steps to create
the
key-chain
.

2
Create and enter into key chain
configuration mode.
router(config)#
key
chain
chain-name
3
Create and enter into key chain
– key configuration mode.
Note: The
key-number
can be
any number between 0-
2147483647.
router(config-keychain)#
key
key-number
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4
Enter the key string that will be
used to authenticate with
neighboring devices.
router(config-keychain-
key)#
key-string
keystring



1
Configure GLBP Object
tracking.
Note: The default priority
decrement value is 10.
router(config-if)#
glbp
group-
number
track
object-number
[
decrement
priority
]
2
(Optional) Configure the GLBP
weighting values.
Note: With GLBP, each of the
Active Virtual Forwarders (AVF)
is
assigned a weight (default is
100); if the defaults are not
altered, then
each of the AVFs
will be equally loaded.
rsouter(config-if)#
glbp
group-
number
weighting
weight
[
lower
lower
] [
upper
upper
]
3
Create a tracked object.
Notes:
The
object-number
can
be any
number between 1 and 1000.
The
line-protocol
parameter
will track the protocol state of
the configured interface. The
ip
routing
parameter will
track the
IP routing capability of an
interface (is it configured with
an IP
address and
operational?).
router(config)#
track
object-
number
interface
interface
{
line-protocol
|
ip routing
}
GLBP Complex Example
In this section, the configuration is extended to show basic GLBP
authentication using key
chains, altering the default load balancing behavior
to weighting, and basic interface (line
protocol) tracking. See Tables 5 and 6
for examples.
Table 5
- R1 Complex Example Configuration Addition
1
Enter privileged EXEC mode.
R1>
enable
2
Enter global configuration
mode.
R1#
configure terminal
3
Create a key chain using the
name
testchain
and enter into
key chain configuration mode.
R1(config)#
key chain testchain
4
Create and enter into key chain
R1(config-keychain)#
key
1
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4
Create and enter into key chain
– key configuration mode using
a
key number of 1.
R1(config-keychain)#
key
1
5
Enter a key string of
test-
string
.
R1(config-keychain-key)#
key-
string
test-string
6
Enter interface configuration
mode.
R1(config-keychain-
key)#
interface
fa1/0
7
Enable GLBP authentication
using the configured key chain
and
group number of 1
R1(config-if)#
glbp 1
authentication

key-chain
testchain
8
Change the default GLBP load
balancing behavior to using
weighting.
R1(config-if)#
glbp 1
load-
balancing weighted
9
Exit into global configuration
mode.
R1(config-if)#
exit
10
Create a tracked object that
will monitor the line protocol
status of the fa0/0 interface
using an object number of 1.
R1(config)#
track 1
interface
fa0/0 line-protocol
11
Enter interface configuration
mode.
R1(config)#
interface
fa1/0
12
Configure GLBP to use the
tracked object to influence its
weighting.
R1(config-if)#
glbp 1
track 1
decrement 50
Table 6
- R2 Complex Example Configuration Addition
1
Enter privileged EXEC mode.
R2>
enable
2
Enter global configuration
mode.
R2#
configure terminal
3
Create a key chain using the
name
testchain
and enter into
key chain configuration mode.
R2(config)#
key chain testchain
4
Create and enter into key
chain – key configuration
mode using a
key number of 1.
R2(config-keychain)#
key
1
5
Enter a key string of
test-
string
.
R2(config-keychain-key)#
key-
string
test-string
6
Enter interface configuration
mode.
R2(config-keychain-
key)#
interface
fa1/0
7
Enable GLBP authentication
using the configured key chain
and
group number of 1.
R2(config-if)#
glbp 1
authentication

key-chain
testchain
8
Change the default GLBP load
balancing behavior to using
weighting.
R2(config-if)#
glbp 1
load-
balancing weighted
9
Exit into global configuration
R2(config-if)#
exit
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9
Exit into global configuration
mode.
R2(config-if)#
exit
10
Create a tracked object that
will monitor the line protocol
status of the fa0/0 interface
using an object number of 1.
R2(config)#
track 1
interface
fa0/0 line-protocol
11
Enter interface configuration
mode.
R2(config)#
interface
fa1/0
12
Configure GLBP to use the
tracked object to influence its
weighting.
R2(config-if)#
glbp 1
track 1
decrement 50
Summary
The expectation of full-time connectivity has certainly gotten
considerably higher over the
last decade. Because of this, a number of
different technologies have been developed to
provide redundancy at every point
within the network. As one of these, FHRPs are used to
provide redundancy; which
one you use depends on the specific deployment and the
vendors that will be
used within the target network. I hope that this article provided some
insight
into the configuration steps that are required to configure GLBP and get it up
and
running.
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