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I have Cisco 2500
2 different subnets
T-1 will be first connection
if this fails, I want to make sure
connection is continuous with switchover.
How do I configure the router to see both and be fail safe?

In article <5mV8d.18$>,
TJR <> wrote:
:I have Cisco 2500
:2 different subnets
:T-1 will be first connection
:if this fails, I want to make sure
:connection is continuous with switchover.
:How do I configure the router to see both and be fail safe?

I suggest you examine Vincent C. Jone's book on high availability
networking with Cisco routers. Also, his WWW site has a whitepaper
that outlines the basic steps.

What you are asking for is somewhat difficult to achieve. It would be
much easier if you were satisfied with the failover happening but with
the active connections being dropped.

If you are willing to go through all the trouble necessary to ensure
that connections are not dropped during the connection failover, then
you should not be using a Cisco 2500 for the job -- you should be
using at least *two* Cisco routers, in case one of them fails (or
in case you want to take the router out of service in order to do
maintenance or upgrades.) You should also be ensuring that all of your
infrastructure leading to your critical hosts is redundant and will
fail over without loss.


The easiest way to configure to prevent connections from being lost
would be to use channel bonding (or multilink PPP, which is a form
of channel bonding) over multiple connections to the same ISP... and
have some mechanism for detecting when channels have failed and taking
them out of service. However, if you use multiple channels to the same ISP
then you just push the problem back one step: the ISP becomes the
single point of failure. So if it is important not to lose connections,
then you should be getting connections from multiple ISPs (and make
sure they don't all use the same long-haul links: a lot of the ISPs
that you see advertised are just resellers of the same underlying
long-haul links.) But if your multiple links are to multiple ISPs
to prevent that "single point" failure, then it becomes quite difficult
to avoid losing any connections, unless you are willing to spend a lot
of money to get the ISPs to cooperate with each other to provide
high availability services to you.
--
Take care in opening this message: My grasp on reality may have shaken
loose during transmission!

In article <5mV8d.18$>,
says...
> I have Cisco 2500
> 2 different subnets
> T-1 will be first connection
> if this fails, I want to make sure
> connection is continuous with switchover.
> How do I configure the router to see both and be fail safe?

implement a routing protocol like RIP V2.

--

hsb

"Somehow I imagined this experience would be more rewarding" Calvin
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