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A mechanism to avoid vrrp flap when low priority but short interval vrrp router bootup

IP.com Disclosure Number: IPCOM000238733D
Publication Date: 2014-Sep-15
Document File: 4 page(s) / 57K

Publishing Venue

The IP.com Prior Art Database

Abstract

The invention will optimize the VRRP backup router behavior. In this way, when a new router joins the VRRP group, it will not cause the old master flap becuase of misconfiguration of this new router.

This text was extracted from a PDF file.
This is the abbreviated version, containing approximately 53% of the total text.

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A mechanism to avoid vrrp flap when low priority but short interval vrrp router bootup

1. VRRP flapping issue

Virtual Router Redundancy Protocol (VRRP) is widely deployed in current network, it is designed to eliminate the single point of failure inherent in the static default routed environment. VRRP specifies an election protocol that dynamically assigns responsibility for a virtual router to one of the VRRP routers on a LAN. The VRRP router controlling the IP address(es) associated with a virtual router is called the Master, and forwards packets sent to these IP addresses. The election process provides dynamic fail&over in the forwarding responsibility should the Master become unavailable. Any of the virtual router's IP addresses on a LAN can then be used as the default first hop router by end&hosts. The advantage gained from using VRRP is a higher availability default path without requiring configuration of dynamic routing or router discovery protocols on every end&host.

The typical topo for VRRP routers looks like this:

But in some scenario, when add a new VRRP router to existed network, it will cause the network flapping. In datacenter network, flapping will be cause unpredictable damage.

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Suppose in the network, the master route priority is 200, interval is 5 seconds.

To improve the higher availability default path, adding a new router, and it priority is 100, and its interval is 1s. Then VRRP flapping will happen like this:

At times 0s, master send its regular advertisement.

At times 1s, new router boots up, and it will wait the vrrp advertisement from master for 3 seconds silently. But there is no advertisement received.

At time 4s, new router will declare itself the as the master and broadcast gratuitous ARP to the downstream switch, switch will forwarded uplink traffic from port 1 to port 2.

At time 5s, old master will send its regular advertisement, and new router find it priority is lower than old master, and...