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QOS on Cisco 1721 for Vonage VoIP -- Where do I start?

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I've got a 1721 as my router with 12.3 ios. It's plugged into a
sonicwall TZ170. I have the linksys RT31P2 Vonage provided plugged into
a lan port on the TZ170 giving it an IP of My "real"
phones are plugged into the phone ports on the Linksys.

The default gateway of the Linksys router is the sonicwall WAN IP,
which in turn has the 1721 as it's default gateway.

Now, what I want to do is to use Qos so that when I'm banging away on
the network, VoIP traffic from the linksys (which, btw, is the only
traffic that will come from that device) will be prioritised for both
download and upload (if possible). I'd like to guarantee say 90-100k of
bandwidth in both directions.

The problem is I have very limited understanding of Qos on cisco, and
consequently don't know what options exist in order to prioritise
traffic. Simply using Qos on the linksys obviously won't work because
it is competing with traffic going to the 1721 which is out of its

I see from the connection monitor on the firewall that the Linksys is
constantly making UDP connections on port 137 to the Vonage servers (a
set of IPs I could define).

I feel the easiest way to do this would be to instruct the 1721 that
all traffic either destined to (linksys) or coming from
it, would be prioritised. I am not sure whether it is possible for the
1721 to "know" where in fact that traffic is heading, given the nating
on the firewall and what not. But it seems to me this option would be
the cleanest.

Another option might be to just flat out prioritise traffic from the
Vonage IPs or for 137 UDP traffic.

So, really, two questions:

1. Which approach (or another maybe that I haven't listed) is the best?
2. Given an answer to (1), how might I go about implementing it.


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You may wish to investigate the Linksys Live 24-Hour Support Help Desk:

Cisco 1700 Series Solution Design Tool:

Cisco Quality of Service ( QoS ) Introduction:

Cisco IOS Software Support Resources:

Hope this helps,

Brad Reese
BradReese.Com Cisco Repair Service Experts
1293 Hendersonville Road, Suite 17
Asheville, North Carolina USA 28803
USA & Canada: 877-549-2680
International: 828-277-7272

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Posts: n/a
Yes, but first I really need some methodological help--which approach
do yout think I should pursue?

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