[c-nsp] 7206 LNS/L2TP using HSRP

[Florian Lohoff]

On Mon, May 07, 2012 at 03:56:46PM +0800, ar wrote:
> Hi Tom.
> Yes, we'll surely do the LAC-LNS balancing.
> I'm just exploring in using HSRP for redundancy.
> Getting some ideas from you guys if this is advisable.

You can do steering and redundancy with LNS IP Address sets
too. 

Given you have to LNS a and b add them with

a'1 & b'1 with priority 10
a'2 & b'2 with priority 20

To steer sessions towards a or b softshut the vpdn groups
a'1 or b'1 so sessions will migrate to the other over time.
(conf / vpdn softshut - will simply deny new sessions and LAC
will send them to other destinations).

In case of a failure on the host of the non shutted vpdn group
sessions will migrate to priority 20 in which case the vpdn
group on the alive host are still enabled.

Using HSRP will drop sessions in unexpected ways and i never
heard of anyone using it.

We prefer sessions timeout on the LAC side, something like 24hours
which will help migrate sessions away from LNS which have scheduled
downtimes. 24h ahead of downtime simply vpdn softshut and your LNS
will be free of subscriber sessions once the downtime comes in.

Flo
-- 
Florian Lohoff                                                 f at zz.de
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