Monday, 24 May 2021

HSRP Vs VRRP Vs GLBP

 

Routing Protocols gives redundancy at layer 3

Redundancy between 2 switches, you connect 2 or more links between them.

Similarly to allow redundancy for your clients, you might want to connect 2 routers as the gateway to exit from the network.

FHRP  First Hop Redundancy Protocol

Gives redundancy at First Hop level gives redundancy at the gateway level

On PC I can configure only one IP address as default gateway. If that device (router) goes down then I would need to configure manually on my PCs the new default gateway.

So from the perspective of PC needs --> First Hop Redundancy

FHRP technology allows the 2 routers to share a single IP address. Or we can say a shared ip address between the 2 routers which is called as the VIP – Virtual IP .where you have the rights to prefer a specific router as forwarding router and another routers as Backup router.

Along with VIP the routers will also share mac address.

Forwarding router is the router which will be answering for the VIP and will forward the traffic .

FHRP establish the relationship between the 2 routers, hellos are exchanges between those routers and incase the forwarding/active/master router goes down then the standby router will become active and will now be answering for the VIP and will forward traffic for the clients.

We have the rights which router to be preferred as forwarding/active/master and backup/standby by manipulating the priority values.

Remember FHRP is the technology it is not the actual implementation.

There are 3 main FHRP Implementations HSRP VRRP AND GLBP

Protocol Features

HSRP -
Hot Standby Protocol

VRRP -
Virtual Redudancy Protocol

GLBP -
Gateway Load
Balancing Protocol

Scope

Cisco Proprietary

IEEE standard

Cisco proprietary

Standard

RFC2281

RFC3768

none

OSI Layer

Layer-3

Layer-3

Layer-2

Load Balancing

No

No

Yes

Multicast Group IP address

224.0.0.2 in version 1 
 224.0.0.102 in version 2

224.0.0.18

224.0.0.102

Transport Port Number

UDP 1985

UDP 112

UDP 3222

Timers

Hello – 3 sec

Advertisement – 1 sec

Hello – 3sec

Hold – 10 sec

Master down time = 3*Advertisement Time
+ Skew TimeSkew
Time = (256- Priority)/256

Hold – 10sec

Election

Active Router:1.Highest Priority2. Highest IP address (Tiebreaker)

Master Router: (*)

Active Virtual Gateway:

1-Highest Priority

1-Highest Priority

2-Highest IP (Tiebreaker)

2-Highest IP (Tiebreaker)

Router Role

One Active Router, One Standby Router , One or more listening Router/s

– One Active Router- One or
 More Backup Routers

One AVG (Active Virtual Gateway)- up to 4 AVF
 Routers on the group
 (Active Virtual Forwarder) passing traffic.
- up to 1024 virtual Routers (GLBP groups)
 per physical interface.

Preempt

If Active Router(Highest Priority) is down and up again, Preempt should be configured to become a Active Router again

 By default Preempt is ON in VRRP,
 If Active Router is down and
up again, It will
automatically become a MasterRouter

If Active Router(Highest Priority) is down
 and up again, Preempt should be configured
 to become a Active Router again.

Group Virtual Mac Address

0000.0c07.acxx

0000.5e00.01xx

0007.b4xx.xxxx

IPv6 support

Yes

No

Yes

 

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