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| − | = Purpose of GLBP =
| + | #Redirect [[GLBP]] |
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| − | :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.
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| − | :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.
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| − | = Other high availability protocols =
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| − | *HSRP [[Hot Standby Router Protocol]]
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| − | *VRRP [[Virtual Router Redundancy Protocol]]
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| − | = GLBP functions =
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| − | *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.
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| − | *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.
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| − | *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.
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| − | = GLBP features =
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| − | *Load sharing: Traffic from LAN clients can be shared by multiple routers.
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| − | *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.
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| − | *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.
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| − | *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.
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| − | = How does GLBP work =
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| − | {|
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| − | [[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"|
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| − | == GLBP Roles ==
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| − | === AVG - Active Virtual Gateway ===
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| − | The Router with the highest priority is chosen as the AVG. The AVG has the responsebility of assigning MAC addresses to the AVF Routers.
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| − | === AVF - Active Virtual Forwarder ===
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| − | 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.
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| − | === Load Balancing ===
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| − | 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
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| − | * Round Robin: The AVG responds to ARP requests in sequence first AVF, second AVF, third AVF, first AVF.... (Default)
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| − | * 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.
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| − | * Weighted: Specifies a load balancing method that is dependent on the weighting value advertised by the gateway.
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| − | | |
| − | === Timers ===
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| − | 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.
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| − | |}
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| − |
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| − | {|
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| − | <pre>
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| − | hostname R1
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| − | !
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| − | interface FastEthernet1/0
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| − | ip address 10.0.0.11 255.0.0.0
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| − | glbp 7 ip 10.0.0.1
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| − | glbp 7 priority 130
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| − | glbp 7 timers msec 200 msec 700
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| − | </pre>
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| − | <pre>
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| − | hostname R2
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| − | !
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| − | interface FastEthernet1/0
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| − | ip address 10.0.0.12 255.0.0.0
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| − | glbp 7 ip 10.0.0.1
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| − | glbp 7 priority 120
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| − | glbp 7 timers msec 200 msec 700
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| − | </pre>
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| − | <pre>
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| − | hostname R3
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| − | !
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| − | interface FastEthernet1/0
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| − | ip address 10.0.0.13 255.0.0.0
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| − | glbp 7 ip 10.0.0.1
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| − | glbp 7 priority 110
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| − | glbp 7 timers msec 200 msec 700
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| − | </pre>
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| − | |}
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| − | [[Category:Cisco]][[Category:CCNP]][[Category:IOS]][[Category:Network]][[Category:CCNP3]][[Category:IOS]]
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