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We have a 3640 with a T1 and a DSL line. When the T1 fails everything routes
over to the DSL nicely.

Is it possible to have SMTP in/out e-mail use the T1 and the WEB surfing use
the DSL ? I still want failover in the event of a failure on one or other,
so if the T1 fails e-mail should use the DSL or if the DSL fails WEB should
use the T1.

I think this can be done with Policy ROuting ???? But not sure if that also
would allow for failover like it does now with weighted static routes.

Thanks
Gary

Gary wrote:
> We have a 3640 with a T1 and a DSL line. When the T1 fails everything routes
> over to the DSL nicely.
>
> Is it possible to have SMTP in/out e-mail use the T1 and the WEB surfing use
> the DSL ? I still want failover in the event of a failure on one or other,
> so if the T1 fails e-mail should use the DSL or if the DSL fails WEB should
> use the T1.
>
> I think this can be done with Policy ROuting ???? But not sure if that also
> would allow for failover like it does now with weighted static routes.

Policy-based routing will allow you to force traffic
on to an interface on the basis if anything you can
identify using an access-list.

What happens if tha nominated interface isn't
reachable will depend on a number of things;
if the nominated interface is an Ethernet-style
one then it's possible for the interface itself
to be "up but not able to route traffic" -
remember that Ehternet wasn't really designed to
be used for telco links! If the DSL presents
proper control-signals [like a serial one
would] then you may be able to achieve
better control over what happens.

"PJML" <> wrote in message
news:4034da3a$...
> Gary wrote:
> > We have a 3640 with a T1 and a DSL line. When the T1 fails everything
routes
> > over to the DSL nicely.
> >
> > Is it possible to have SMTP in/out e-mail use the T1 and the WEB surfing
use
> > the DSL ? I still want failover in the event of a failure on one or
other,
> > so if the T1 fails e-mail should use the DSL or if the DSL fails WEB
should
> > use the T1.
> >
> > I think this can be done with Policy ROuting ???? But not sure if that
also
> > would allow for failover like it does now with weighted static routes.
>
> Policy-based routing will allow you to force traffic
> on to an interface on the basis if anything you can
> identify using an access-list.
>
> What happens if tha nominated interface isn't
> reachable will depend on a number of things;
> if the nominated interface is an Ethernet-style
> one then it's possible for the interface itself
> to be "up but not able to route traffic" -
> remember that Ehternet wasn't really designed to
> be used for telco links! If the DSL presents
> proper control-signals [like a serial one
> would] then you may be able to achieve
> better control over what happens.
>

The 2 lines in question are a T1 and DSL line. I guess the question is 'Does
Policy Based routing care if the link is up or down with regards to routing'
?

i.e Will they fail over even with PBR in operation.

Gary

In article <0a7Zb.6072$iB.396@lakeread06>, Gary <> wrote:
>
>"PJML" <> wrote in message
>news:4034da3a$...
>> Gary wrote:
>> > We have a 3640 with a T1 and a DSL line. When the T1 fails everything
>routes
>> > over to the DSL nicely.
>> >
>> > Is it possible to have SMTP in/out e-mail use the T1 and the WEB surfing
>use
>> > the DSL ? I still want failover in the event of a failure on one or
>other,
>> > so if the T1 fails e-mail should use the DSL or if the DSL fails WEB
>should
>> > use the T1.
>> >
>> > I think this can be done with Policy ROuting ???? But not sure if that
>also
>> > would allow for failover like it does now with weighted static routes.
>>
>> Policy-based routing will allow you to force traffic
>> on to an interface on the basis if anything you can
>> identify using an access-list.
>>
>> What happens if tha nominated interface isn't
>> reachable will depend on a number of things;
>> if the nominated interface is an Ethernet-style
>> one then it's possible for the interface itself
>> to be "up but not able to route traffic" -
>> remember that Ehternet wasn't really designed to
>> be used for telco links! If the DSL presents
>> proper control-signals [like a serial one
>> would] then you may be able to achieve
>> better control over what happens.
>>
>
>The 2 lines in question are a T1 and DSL line. I guess the question is 'Does
>Policy Based routing care if the link is up or down with regards to routing'
>?
>
>i.e Will they fail over even with PBR in operation.
>
>Gary

Yes: Policy based routing can be configured to fail over if a link goes
down.

BUT!!!! The fail over will only occur if there is some way for the
router to detect that the link has gone down (easy for a point-to-point
T1, not so easy for a DSL link, particularly if an external modem
connected via ethernet, which never goes down).

Note that if either path is doing NAT, all open connections will drop
when a failover occurs.

Good luck and have fun!
--
Vincent C Jones, Consultant Expert advice and a helping hand
Networking Unlimited, Inc. for those who want to manage and
Tenafly, NJ Phone: 201 568-7810 control their networking destiny
http://www.networkingunlimited.com

On Thu, 19 Feb 2004 13:22:42 -0500, "Gary" <>
wrote:
>
>The 2 lines in question are a T1 and DSL line. I guess the question is 'Does
>Policy Based routing care if the link is up or down with regards to routing'
>?
>
>i.e Will they fail over even with PBR in operation.

As mentioned, failover with PBR can be hard because typically the link
has to change state to 'down' before PBR will notice. Link
availability verification via CDP came along fairly recently, but it's
of little use most of the time. The newest feature that addresses
this issue is much more optimal, but it's only available as of
12.3(4)T. It allows PBR to track things such as IP address
reachability via ping to determine when a link is up. See
http://www.cisco.com/en/US/products/...0801d1e95.html

-Terry

"Vincent C Jones" <> wrote in message
news:c137md$786$...
> In article <0a7Zb.6072$iB.396@lakeread06>, Gary <>
wrote:
>> SNIP <<
>
> Yes: Policy based routing can be configured to fail over if a link goes
> down.
>
> BUT!!!! The fail over will only occur if there is some way for the
> router to detect that the link has gone down (easy for a point-to-point
> T1, not so easy for a DSL link, particularly if an external modem
> connected via ethernet, which never goes down).
>
> Note that if either path is doing NAT, all open connections will drop
> when a failover occurs.
>
> Good luck and have fun!
> --
> Vincent C Jones, Consultant Expert advice and a helping hand
> Networking Unlimited, Inc. for those who want to manage and
> Tenafly, NJ Phone: 201 568-7810 control their networking destiny
> http://www.networkingunlimited.com

Haven't tested this *exact* scenario, but ones similar.

Create a GRE tunnel that can only be established over the DSL. It will go
done if anything in the DSL path goes awry. Use that interface with PBR.

Yes, there are details to work through. Dynamic vs. static routing on DSL,
etc. could keep things interesting for a while.

Happy routing!

"Terry Baranski" <0VE> wrote in message
news:...
> On Thu, 19 Feb 2004 13:22:42 -0500, "Gary" <>
> wrote:
> >
> >The 2 lines in question are a T1 and DSL line. I guess the question is
'Does
> >Policy Based routing care if the link is up or down with regards to
routing'
> >?
> >
> >i.e Will they fail over even with PBR in operation.
>
> As mentioned, failover with PBR can be hard because typically the link
> has to change state to 'down' before PBR will notice. Link
> availability verification via CDP came along fairly recently, but it's
> of little use most of the time. The newest feature that addresses
> this issue is much more optimal, but it's only available as of
> 12.3(4)T. It allows PBR to track things such as IP address
> reachability via ping to determine when a link is up. See
>
http://www.cisco.com/en/US/products/...0801d1e95.html
>
> -Terry

The router in question houses both the DSL and T1, and Dialer0 is ip
unnumbered FastEthernet0/0 so effectively the T1 and DSL have the same IP.

As the DSL is in the same box as the T1, is it true the PBR will see the
link fail on the DSL, or will it always be up as there is a cable connected
to it.

Gary

On Fri, 20 Feb 2004 22:51:13 -0500, "Gary" <>
wrote:
>> As mentioned, failover with PBR can be hard because typically the link
>> has to change state to 'down' before PBR will notice. Link
>> availability verification via CDP came along fairly recently, but it's
>> of little use most of the time. The newest feature that addresses
>> this issue is much more optimal, but it's only available as of
>> 12.3(4)T. It allows PBR to track things such as IP address
>> reachability via ping to determine when a link is up. See
>>
>http://www.cisco.com/en/US/products/...0801d1e95.html
>>
>> -Terry
>
>The router in question houses both the DSL and T1, and Dialer0 is ip
>unnumbered FastEthernet0/0 so effectively the T1 and DSL have the same IP.
>
>As the DSL is in the same box as the T1, is it true the PBR will see the
>link fail on the DSL, or will it always be up as there is a cable connected
>to it.

PBR won't see the link fail unless it changes state to down. The
feature above, however, allows PBR to monitor the reachability of a
next-hop via ping and to failover (either to another next-hop or do
standard destination-based routing) if a next-hop becomes unreachable.

-Terry