concept behind vrrp

[r.kukreja]

can any body explain concept of vrrp and where and how can i use vrrp protocol

[Marcel Zehnder]

hi

VRRP is a first hop redundancy protocol. Check out the configuration guide for a good explanation and configuration examples:

http://www.cisco.com/en/US/partner/docs/ios/ipapp/configuration/guide/ipapp_vrrp_ps6441_TSD_Products_Configuration_Guide_Chapter.html

[Jon Marshall]

r.kukreja wrote:
can any body explain concept of vrrp and where and how can i use vrrp protocol

VRRP is used to provide a redundant default-gateway to end clients. As well as VRRP Cisco also support HSRP and GLBP. They are all deisgned to do a similiar thing with slight differences.

Imagine a scenario where you have an access-layer switch with a PC connected into it. This access-layer switch is connected to 2 distribution switches for redundancy ie. if one of the distribution switches fails then the other can be used.  But there is a problem with that. The client is in vlan 10 on the access-layer switch and each distribution switch has a L3 vlan interface for vlan 10 eg.

distro1

=====

int vlan 10

ip address 192.168.5.2 255.255.255.0

distro2

=====

int vlan 10

ip address 192.168.5.3 255.255.255.0

the problem is which IP address do you use for the PC as the default-gateway ? if you use 192.168.5.2 then if that switch fails then the address is 192.168.5.3 so that won't work any more because the PC no longer has connectivity. So the solution is to use one of VRRP/HSRP/GLBP. What these allow you to do is add extra config under the vlan 10 interfaces on the distro switches so that an IP address is shared between the interfaces. HSRP example but VRRP is doing the same thing -

distro1

=====

int vlan 10

ip address 192.168.5.2 255.255.255.0

standby 10 ip 192.168.5.1

standby 10 priority 110

standby 10 preempt

distro2

=====

int vlan 10

ip address 192.168.5.3 255.255.255.0

standby 10 ip 192.168.5.1

standby 10 pri 100

standby 10 preempt

notice that the 192.168.5.1 address is common to both interfaces. Now you point the client to 192.168.5.1 and it will use that address. If distro1 fails then distro2 can now start to use 192.168.5.1 and so the PC can still get connectivity.

That is basically how VRRP works.

Jon

[hardiklodhia]

Hi, In addition to above post, VRRP is standard based (RFC 3768- VRRP, IETF) protocol and works as first hop redundancy protocol. In VRRP, you can use the same IP address that the interface already has as the virtual IP address where HSRP does not, you need to allocate an additional address.

In Vrrp all none-master routers in the group are in backup state. Whereas In HSRP, one router is active, one is standby and the rest are in listening state. this is if more than 3 routers are in the group.

In vrrp, if a router uses virtual ip as an interface ip, this router becomes the active. If the priorities are default. In HSRP the highest interface address wins the election.

HTH,

[r.kukreja]

the link is not getting open.

other discussions are also useful, can any body explain with example for master and non master routers in case of vrrp