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Design help: T1 backing up Metro Enet

 
 
bigbrorpi@gmail.com
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      09-12-2005
Hi -

I have two 3750s SMI at my main site running HSRP.
I have another network at a remote site and both metro ethernet and a
T1 between them.
I'm looking for the best way to do automated failover. The metro
ethernet is the primary connection and the T1 is a backup. I have a
2950 at the remote site.

What is the best way to make this work in the most redundant fashion
possible?
I was thinking that I should have an L3 switch at the remote site with
the T1 router hanging off of it. Any other ideas thatm ight be more
cost-effective?

Thanks!

 
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Vincent C Jones
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      09-13-2005
In article <(E-Mail Removed) .com>,
<(E-Mail Removed)> wrote:
>Hi -
>
>I have two 3750s SMI at my main site running HSRP.
>I have another network at a remote site and both metro ethernet and a
>T1 between them.
>I'm looking for the best way to do automated failover. The metro
>ethernet is the primary connection and the T1 is a backup. I have a
>2950 at the remote site.
>
>What is the best way to make this work in the most redundant fashion
>possible?
>I was thinking that I should have an L3 switch at the remote site with
>the T1 router hanging off of it. Any other ideas thatm ight be more
>cost-effective?
>
>Thanks!


If this is set up as independent networks (separate IP address
space at each end), it is trivial to implement using basic routing
protocols as even RIP would do the job.

If this is set up as an extended LAN, you'll need to enable spanning
tree on every link between every bridge/switch that supports a link
between the two sites and adjust your metrics so the T1 selected
only if no other cross links remain. Again, a trivial setup to implement
if you read the manuals and look at how spanning tree does its thing.

A few hints:

* If you're using an extended LAN, you are not going to be happy when
fail over to the T1. Performance will not be adequate unless your
traffic is minimal (including background broadcasts).

* Whether routing or bridging, you need to routinely test the T1 to
detect failure while it is not in use. Otherwise, when you finally do
need it, it probably won't be working.

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
 
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bigbrorpi@gmail.com
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      09-13-2005
Vincent -

Thanks for the reply.
It would be separate networks. I tried running RIP, but couldn't seem
to get it to detect the link as being down. Furthermore, the aging time
was atrocious.
I was trying to use ping tracking via the SLA Monitor function within
my static routes (there are nonly two routes at the distant end since
all traffic is routed to the main site). Thsi worked fairly well at the
remote site, but my 3750s don't seem to support it (even though it
would appear that they should through the Software Advisor). From what
I can see, the ping tracking (they call it ICMP Echo Operation) is
supported, but it looks like alot of that changed in 12.3 - which isn't
available for the 3750s. Would you happen to know if I can accomplish
this?

Thanks
B

 
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bigbrorpi@gmail.com
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      09-13-2005
Vincent -

I was just re-reading my original post and realized that I forgot to
mention my key problem!
The metro ethernet link never goes down in the eyes of my CPE. The
transceivers that my providers has given me (Tasman boxes) always have
the ethernet link up even if the WAN side is down.
I'm struggling with how to actually know that the link failed.

 
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Vincent C Jones
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      09-13-2005
In article <(E-Mail Removed) om>,
<(E-Mail Removed)> wrote:
>Vincent -
>
>I was just re-reading my original post and realized that I forgot to
>mention my key problem!
>The metro ethernet link never goes down in the eyes of my CPE. The
>transceivers that my providers has given me (Tasman boxes) always have
>the ethernet link up even if the WAN side is down.
>I'm struggling with how to actually know that the link failed.
>


With routers at both ends of the link, any routing protocol should do
the job. I'm assuming your metroEthernet goes end to end, not via VPN
over the Internet. If the latter, its slightly more difficult (see the
white paper on my web site on providing alternative routing for VPNs).

As for response time of RIP, if it otherwise worked, go back to it and
adjust the timers to get the response to failure down to something
reasonable. You should be able to get failover to function in under 10
seconds whereas with default timers it will take three minutes.

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
 
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bigbrorpi@gmail.com
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      09-13-2005
I'll have to try it again... I wasn't able to get RIP working at all.
Let me give it another shot and I'll post back.

Thanks
B

 
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Doug McIntyre
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      09-14-2005
http://www.velocityreviews.com/forums/(E-Mail Removed) writes:
>I was just re-reading my original post and realized that I forgot to
>mention my key problem!
>The metro ethernet link never goes down in the eyes of my CPE. The
>transceivers that my providers has given me (Tasman boxes) always have
>the ethernet link up even if the WAN side is down.
>I'm struggling with how to actually know that the link failed.



One option is to use router tracking objects. Fairly new though, so
it'll be 12.3.something. Track ICMP out across, and setup floating
routes to handle the case of the MOE being up or down.

 
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