>
> > >Hi everybody:
>> >I am study BSCN,there are something confused me:
>> >in the book they says:The highest IP address on an active interface is
>> >normally used as the router ID, but this can be overridden by
>>configuring an
>> >IP address on a loopback interface.
>> >I want to know which will be the Router ID if the loopback IP address
>> >smaller than the active interface IP address?
>> >Any suggestion will be appreciate,thanks.
>> >
>> >Will Guan
>> >frome Peking, China
>>
>> If there are multiple loopback, the router ID will be the numerically
>> highest IP address on any loopback. In other words,
> [snip]
[EMAIL PROTECTED] quite correctly added,
>And the part that some folks forget is that once a router ID is active,
>it will not change if another interface is made active, or the IP of
>another interface is changed to a higher value. The rationale is
>stability, since all other routers in the area are tracking this one
>by its present router ID. The same principle applies to the DR election
>-- there is no coup option.
>
>Now if you were to shut down the interface with the existing router ID...
To follow up on a discussion yesterday as to when high and low
parameter values win an election...
As Marty observes, the OSPF router ID, once OSPF is initialized, will
not change. When the OSPF DR is elected on a subnet, a more-preferred
router will not become DR unless the original DR goes down. I
_think_ this is the behavior of an ISIS pseudonode, but I'd have to
research that.
In HSRP, however, you can designate a primary and secondary. If the
secondary takes over but the primary returns, you can set the primary
for Marty's coup d'etat option -- it will take back control.
Spanning tree also supports a coup by the root bridge.
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