3com 3031 Instruccion De Instalación

C

HAPTER

 75: VRRP C

ONFIGURATION

In non-preemption mode, once a router in the standby group becomes the 
MASTER router, other routers, even configured with higher priority later, cannot 
become the MASTER router. If a router working in preemption mode finds that its 
own priority is higher than that of the present MASTER router, it will become the 
MASTER router, and the former MASTER router will become the STANDBY router. 

Along with preemption mode, delay can also be configured. This will delay the 
coming of the point when the STANDBY router becomes the MASTER router. This 
ensures that in an unstable network if the STANDBY router has not received the 
packets from the MASTER router punctually, it will become the MASTER router 
(failure of STANDBY to receive the packets may be due to network congestion, not 
due to malfunction of the MASTER router). Therefore, a delay will ensure the 
reception of the packet from the MASTER router and thus avoid frequent state 
switchover.

The delay is set in second ranging 0 to 255.

Perform the following configuration in interface view.

The default mode is preemption with a delay of 0 second.

VRRP provides two authentication methods:

■

SIMPLE: Simple character authentication

■

MD5: MD5 authentication

In a secure network, authentication can adopt the default configuration, which 
means no authentication will be conducted by the router to the VRRP packets 
being sent out. And the router receiving the VRRP packets will take them as true 
and legal without any authentication. In this case no authentication key is needed.

In a network under possible security threat, the authentication method can be 
configured to SIMPLE. This means the router sending out the VRRP packets will fill 
the authentication key into the VRRP packets, while the router receiving the VRRP 
packet will compare the authentication key of the packet with the locally 
configured authentication key. If they are the same, the packet will be taken as a 
true and legal one. Otherwise it will be regarded as an illegal packet to be 
discarded. In this case, you should set the authentication key not longer than 8 
bytes. 

In an unsafe network, the authentication method can be configured to MD5. The 
router will use the authentication method and MD5 algorithm provided by the 

Table 1105   Configuring the preemption mode and delay of standby group routers

Configure the preemption mode 
and delay

 

 

[ timer delay delay-value ]

Delete preemption mode