Re: INE Workbook

Hi Bilal,

The SLA is sending icmp's to the configured IP address, which gives the SLA
a state, I believe with icmpecho you can have three states "OK, timeout or
over threshold" the OK means that the echo-reply returned within the
configured time threshold, over threshold means it returned but outside of
the threshold and timeout means that the device you are sending the icmp
echo to is completely unreachable.

You are then tracking these return codes with the enhanced object tracker,
which is a separate function in IOS that is used to track things such as
interface protocols, routes in routing table and ip sla... the ip sla
support for enhanced object tracker however is not available in the ip base
version of IOS..

The enhanced object tracker was originally created to for HSRP I believe so
it could track if an interface went down and force the backup gateway to
takeover but grew into this beautiful beast we used today.

So here in this example, we are configuring the enhanced object tracker to
track the state of the IP SLA so when the IP SLA returned a code of DOWN the
trackers state also changes to DOWN and vice versa.

The Object tracker is then attached to the static route, the purpose of this
is that IF the object tracker state is UP then the route will be installed
into the route table, if the object tracker state is DOWN then the route
will be removed from the route table...

the RIP process is configured to conditionally inject a default route, based
on the condition in the route-map that it is configured for, in this
instance the condition in the route map is that the dummy route is in the
routing table, if it is not in the routing table the default route will not
be generated by RIP.

You do not necessarily have to use a dummy route, you could use a static
default route if you wished, it doesn't really matter the purpose of the
objective is to show you that you can force RIP to advertise a default route
based on a condition in a route map :-)

and no one is ever a pain by trying to understand something we all have to
learn somehow! :-)

HTH

Garth

On Sat, Aug 7, 2010 at 1:31 PM, Bilal Hansrod <bilal.hansrod_at_gmail.com>wrote:

> Thanks Garth,
>
> I still couldn't get my head around of using the dummy route. How come it
> disappear from R4 routing table when I am unable to reach BB3. I did in past
> used sla monitor on ASA but I was tracking my defaut route and switch to
> backup route if the destination is unreachable.
>
> Sorry for the pain, but can I do without dummy route. Is it done via dummy
> route, because I don't have static default route.'
>
> Thanks,
>
> Bilal
>
>
> On Sat, Aug 7, 2010 at 2:55 PM, Garth Bryden <
> hacked.the.planet.on.28.8k.dialup_at_gmail.com> wrote:
>
>> Hiya,
>>
>> They use a dummy which will be removed from the route table if the SLA
>> fails.. this is because they need to use a static route to configure the
>> tracking with... you could probably use a default route as the dummy route
>> pointing to null0 since that is purpose of the advertisement anyway.. I
>> guess it doesn't really matter as long as it doesn't leak into the rest of
>> your routing domain or outside and doesn't affect your routing!
>>
>> On Sat, Aug 7, 2010 at 12:30 PM, Bilal Hansrod <bilal.hansrod_at_gmail.com
>> > wrote:
>>
>>> Hi All,
>>>
>>> I was doing INE workbook 1 and was bit lost in one of the technology lab.
>>> The topic is RIPv2 Reliable Conditional Default Routing in which I
>>> couldn't
>>> understand why DUMMY route was used to track the reachability of BB3. Any
>>> thoughts -
>>>
>>> Bilal
>>>
>>>
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Received on Sat Aug 07 2010 - 14:05:14 ART