Glbp Virtual Gateway Redundancy; Glbp Virtual Forwarder Redundancy - Cisco Nexus 7000 Series Configuration Manual

Chapter 18 Configuring GLBP
S e n d d o c u m e n t c o m m e n t s t o n e x u s 7 k - d o c f e e d b a c k @ c i s c o . c o m .

GLBP Virtual Gateway Redundancy

GLBP provides virtual gateway redundancy. A member in a group can be in the active, standby, or listen
state. GLBP uses a priority algorithm to elect one gateway as the AVG and elect another gateway as the
standby virtual gateway. The remaining gateways go into the listen state. You can configure the GLBP
priority on each gateway. If the GLBP priority is identical on multiple gateways, GLBP uses the gateway
with the highest IP address as the AVG.
If an AVG fails, the standby virtual gateway assumes responsibility for the virtual IP address. GLBP
elects a new standby virtual gateway from the gateways in the listen state.

GLBP Virtual Forwarder Redundancy

GLBP provides virtual forwarder redundancy. Virtual forwarder redundancy is similar to virtual gateway
redundancy with an active virtual forwarder (AVF). If the AVF fails, a secondary virtual forwarder in the
listen state assumes responsibility for the virtual MAC address. This secondary virtual forwarder is also
a primary virtual forwarder for a different virtual MAC address. GLBP migrates hosts away from the old
virtual MAC address of the failed AVF, using the following two timers.
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GLBP uses hello messages to communicate the current state of the timers.
In Figure
192.0.2.1. Router A is also an AVF for the virtual MAC address 0007.b400.0101. Router 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 192.0.2.1, the virtual IP address, and a gateway MAC
address of 0007.b400.0101 that points to router A. 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.
OL-20002-02
Redirect timer—Specifies the interval during which the AVG continues to redirect hosts to the old
virtual MAC address. When the redirect time expires, the AVG stops using the old virtual MAC
address in ARP replies, although the secondary virtual forwarder continues to forward packets that
were sent to the old virtual MAC address.
Secondary hold timer—Specifies the interval during which the virtual MAC address is valid. When
the secondary hold time expires, GLBP removes the virtual MAC address from all gateways in the
GLBP group and load balances the traffic over the remaining AVFs. The expired virtual MAC
address becomes eligible for reassignment by the AVG.
18-1, router A is the AVG for a GLBP group and is responsible for the virtual IP address
Cisco Nexus 7000 Series NX-OS Unicast Routing Configuration Guide, Release 4.x
Information About GLBP
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