In every host within the organization network there are should be a need for router as default gateway for every host to the connect to Internet. But what if the gateway router goes offline or the default gateway IP changed during configurations?
Replacing the gateway
routers will be cause a longer service interruption to users within the
organization and that is not reactive way to the handle the issue. This is
where FHRP will be take places.
The below diagram is
an examples of the network topology without (FHRP) implementations:
What is First Hop Redundancy Protocol (FHRP)?
(FHRP) is hop
redundancy protocol that are designed to the provide redundancy the gateway
router within the organization network by use of a virtual IP address & virtual
MAC address.
To implements FHRP,
there are should be two or more routers that will used as gateways router. The
virtual IP addresses & virtual MAC address will have used on both routers. The
virtual IP address will the default gateway IP address for all the devices
inside the organization networks. One router will have used as active router
& the other router will be standby. If active router goes offline the stand
by router will be take its place to the gateway routers for all the hosts.
The below diagrams
are example of the network topology with (FHRP) implemented:
First Hop Redundancy Protocol (FHRP) Options
We have three ways to
the implement FHRP. These are by the using following (FHRP)
Hot Standby Router Protocol (HSRP)
Hot Standby Router
Protocol is Cisco-proprietary router redundancy protocol that enable a
cluster of the routers to cooperate, and all routers are willing to be default
router. All routers within cluster will have the same virtual IP address &
virtual mac address.
The Two (HSRP) Router
States are:
·
Active Router–that actively sends & receives the
packet to the host within organization. It’s the default gateway routers. Only
one active router will have selected among the cluster of the routers.
·
Standby Router–that in case the incumbent active
router will be go offline among the standby router will chose as active routers.
If active router goes
offline router failover will be occur. These changes will be not affect the
hosts. The host keeps the same IP address & MAC addresses settings. The default
gateway IP address will the same still on all the hosts. There will be no
changes on host’s ARP table as gateway router virtual MAC address will the
same. Changes in the failover only happen on the router and switch and hosts the
not affected.
2. Virtual Router
Redundancy Protocol (VRRP)
Virtual Router
Redundancy Protocol are vendor-neutral redundancy protocol that groups a
cluster of the physical routers (two or more routers) to the produce a new
single virtual router. It’s enables redundancy by the assigning same virtual
gateway IP address & MAC address on all the physical routers within VRRP
group. Currently VRRP is at version 2. It’s almost has the same concept like
HSRP. The only difference is that pre-emption is enabled by the default on VRRP
while on HSRP it’s needs to be the configured manually.
Two states of the (VRRP)Virtual
Router Redundancy Protocol following are:
·
Master Router– It’s the current default gateway of all hosts within the
organization. It’s actively sending & receiving packets to hosts.
·
Backup Router – The backup router will be take role of the master router
during when the failover or when the master router’s goes offline.
3. Gateway Load
Balancing Protocol (GLBP)
As compared to HSRP
and VRRP, GLBP are bit different. With the GLBPP routers within the group are
allowed to do load balancing. To the put it simply, all traffic that are
transmitted to the default gateway IP address will load-balanced one at the
time or in the round-robin manner among the routers within the group. GLBP the
same state as HSRP, which is called active & standby. The mechanism of the
GLBP active & standby state are same as HSRP active and standby states.
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