Difference between revisions of "Gateway Load Balancing Protocol"

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= Purpose of GLBP =
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#Redirect [[GLBP]]
 
 
:The purpose of GLBP is to ensure network connectivity in case of Router or access circuit failure. GLBP automatically Load balances the load from the IP traffic sources.
 
 
 
:Gateway Load Balancing Protocol (GLBP) is a Cisco proprietary protocol that attempts to overcome the limitations of existing redundant router protocols by adding basic load balancing functionality.
 
 
 
= Other high availability protocols =
 
*HSRP [[Hot Standby Router Protocol]]
 
*VRRP [[Virtual Router Redundancy Protocol]]
 
 
 
= GLBP functions =
 
*Active virtual gateway (AVG): Members of a GLBP group elect one gateway to be the 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 group.
 
*Active virtual forwarder (AVF): Each gateway assumes responsibility for forwarding packets sent to the virtual MAC address assigned to it by the AVG. These gateways are known as AVFs for their virtual MAC address.
 
*Communication: GLBP members communicate with each other using hello messages sent every 3 seconds to the multicast address 224.0.0.102, User Datagram Protocol (UDP) port 3222.
 
 
 
= GLBP features =
 
*Load sharing: Traffic from LAN clients can be shared by multiple routers.
 
*Multiple virtual routers: Up to 1,024 virtual routers (GLBP groups) can be on each physical interface of a router, and there can be up to four virtual forwarders per group.
 
*Preemption: You can preempt an AVG with a higher priority backup virtual gateway. Forwarder preemption works in a similar way, except that it uses weighting instead of priority and is enabled by default.
 
*Efficient resource utilization: Any router in a group can serve as a backup, which eliminates the need for a dedicated backup router because all available routers can support network traffic.
 
= How does GLBP work =
 
{|
 
|
 
[[Image:GLBP1.png|thumb|500px|float|Picture 1: GLBP group with Router R1 as AVG and AVF and Router R2 and R3 as AVF]]
 
|valign="top"|
 
== GLBP Roles ==
 
=== AVG - Active Virtual Gateway ===
 
The Router with the highest priority is chosen as the AVG. The AVG has the responsebility of assigning MAC addresses to the AVF Routers.
 
=== AVF - Active Virtual Forwarder ===
 
The AVF Routers Route traffic from the connected clients. Each AVF is assigned its own MAC-Address. The MAC-Address is assigned from the AVG.
 
=== Load Balancing ===
 
When the clients broadcast [[ARP]] requests to get the MAC Address of the default gateway - 10.0.0.1 - the AVG responds with a MAC-Address of one of the AVF's. load balancing can be either
 
* Round Robin: The AVG responds to ARP requests in sequence first AVF, second AVF, third AVF, first AVF....  (Default)
 
* Host dependent: Specifies a load balancing method based on the MAC address of a host where the same forwarder is always used for a particular host while the number of GLBP group members remains unchanged.
 
* Weighted: Specifies a load balancing method that is dependent on the weighting value advertised by the gateway.
 
 
 
=== Timers ===
 
Default the hello time for GLBP is 3 seconds and holdtime is 10 seconds. In the example hello time is set to 0.25 second and holdtime is 0.7 second.
 
|}
 
 
{|
 
|
 
<pre>
 
hostname R1
 
!
 
interface FastEthernet1/0 
 
  ip address 10.0.0.11 255.0.0.0
 
  glbp 7 ip 10.0.0.1
 
  glbp 7 priority 130
 
  glbp 7 timers msec 200 msec 700
 
</pre>
 
|
 
<pre>
 
hostname R2
 
!
 
interface FastEthernet1/0
 
  ip address 10.0.0.12 255.0.0.0
 
  glbp 7 ip 10.0.0.1
 
  glbp 7 priority 120
 
  glbp 7 timers msec 200 msec 700
 
</pre>
 
|
 
<pre>
 
hostname R3
 
!
 
interface FastEthernet1/0
 
  ip address 10.0.0.13 255.0.0.0
 
  glbp 7 ip 10.0.0.1
 
  glbp 7 priority 110
 
  glbp 7 timers msec 200 msec 700
 
</pre>
 
|}
 
 
 
[[Category:Cisco]][[Category:CCNP]][[Category:IOS]][[Category:Network]][[Category:CCNP3]]
 

Latest revision as of 06:05, 4 May 2009

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