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VRRP (Virtual Router Redundancy Protocol) Configuration
Issue 1 July 2006 177
Configuration is performed on a per-interface basis. When a netbios broadcast packet arrives
from an interface on which netbios rebroadcast is enabled, the packet is distributed to all other
interfaces configured to rebroadcast netbios.
If the netbios packet is a net-directed broadcast (e.g., 149.49.255.255), the packet is relayed to
all other interfaces on the list, and the IP destination of the packet is replaced by the appropriate
interface broadcast address.
If the netbios broadcast packet is a limited broadcast (e.g., 255.255.255.255), it is relayed to all
VLANs on which there are netbios-enabled interfaces. In that case, the destination IP address
remains the limited broadcast address.
NetBIOS Re-broadcast Configuration CLI Commands
VRRP (Virtual Router Redundancy Protocol) Configuration
VRRP Overview
VRRP is an IETF protocol designed to support redundancy of routers on the LAN, as well as
load balancing of traffic. VRRP is transparent to host stations, making it an ideal choice when
redundancy, load balancing and ease of configuration are all required.
The concept underlying VRRP is that a router can backup other routers, in addition to
performing its primary routing functions. This redundancy is achieved by introducing a virtual
router. A virtual router is a routing entity associated with multiple physical routers. The routing
functions of the virtual router are performed by one of the physical routers with which it is
associated. This router is known as the master router. For each virtual router, VRRP selects a
master router. If the selected master router fails, another router is selected as master router.
In VRRP, two or more physical routers can be associated with a virtual router, thus achieving
extreme reliability. In a VRRP environment, host stations interact with the virtual router. They
are not aware that this router is a virtual router, and they are not affected when a new router
In order to... Use the following command...
Set NetBIOS rebroadcasts
mode on an interface
ip netbios-rebroadcast
Disable NetBIOS rebroadcasts
mode on an interface
no ip netbios-rebroadcast