IP Services - First-Hop Redundancy Protocol

11 important questions on IP Services - First-Hop Redundancy Protocol

What is the Hot Standby Router Protocol?

It is a Cisco proprietary protocol that provides transparent failover of the first hop device (Default Gateway)

What are the basics of Hot Standby Router Protocol?

- minimum of two devices.

- A virtual IP address is configured on the HSRP enabled interfaces

- Active router is chosen which assumes the IP address and MAC address and routes the packets for the network.

- Active router is chosen by priority (Default 100, higher is better) or highest IP address on LAN segment in case of a Tie

What are the differences between HSRPv1 and HSRPv2?

1. Timers: V1 does not support millisecond time values, v2 does.

2. Group range: V1 0-255 and for V2 it's 0-4095

3. Multicast address: V1 and for V2 it's

4. MAC address range:
        - V1 is 00:00:0C:07:AC:xy where xy is hex value of group number
        - V2 is 00:00:0C:9F:F0:00 thru  00:00:0C:9F:FF:FF
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What is the command for defining an HSRP Instance?

Standby {instance-id} IP {vip-address}

How can HSRP use object tracking?

If a track is created for an object for example, this track can be linked to priority in HSRP.
With the command standby 10 track 1 decrement 20 the priority is decremented by 20 when the track 1 object fails.

Whereas HSRP is a Cisco proprietary protocol, another protocol named Virtual Router Redundancy Protocol is an industry standard.
VRRP is very similar to HSRP, what are the main differences to be noted?

1. Active router is called Master Router, others are called Backup Routers

2. VRRP enables Preemption (Switchback to primary) by default

3. The MAC address of the VIP gateway uses 00:00:5E:00:01:xx where xx is hex value of group id

4. VRRP uses multicast address for communication

What versions of VRRP are there?

VRRPv2: Supports IPv4
VRRPv3: Supports IPv4 and IPv6

What is the important difference between the Legacy VRRP configuration and the newer Hierarchical VRRP configuration?

1. Legacy CLI config only supports VRRPv2
2. Hierarchical can be configured by enabling VRRPv3
3. Hierarchical creates a multi-address hierarchical CLI format.

What is Global Load Balancing Protocol (GLBP)?

GLBP is a gateway redundancy and load balancing protocol which can be used on a network segment.

What are the 2 roles within the GLBP?

1. Active Virtual Gateway (AVG): There is one AVG per GLBP group, which responds to initial ARP requests for the VIP address. It responds with the MAC address of the AVF

2. Active Virtual Forwarder (AVF): There can be up to 4 AVFs. The AVF routes traffic received from the assigned hosts.

What is the default load balancing method used by GLBP, and what are the 3 supported ones?

1. Round Robin (Default)
2. Weighted (Defines weights to each device, larger router can route more traffic)
3. Host Dependent (uses the host mac address so the host always uses the same Virtual MAC)

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