From: Scott Vermillion (scott_ccie_list.com@it-ag.com)
Date: Thu Sep 13 2007 - 18:15:15 ART
Hey Joe,
If I read Mihai correctly, his issue is the sheer volume of spokes. I think
in your best practice architecture, he would still be facing 500 spokes on a
given router. Thus, my stab in the dark was to simply split the load across
four HE routers (250 spokes to 1 & 2 and 250 spokes to 3 & 4). The SLB
thing looks slick but might be overly complex/expensive for what he's trying
to accomplish. Looks like just spokes reaching into a centralized hub, sans
any spoke-to-spoke requirement (speculation on my part). Perhaps DMVPN in
this case is attractive simply because he doesn't want to hassle with fixed
IPs at all of the spokes (NHRP) or he just wants to simplify his HE configs,
or likely even both. I dunno.
Static routing might allow for more spokes on a single box, but I don't
think Cisco is in favor of that approach, so there's likely nothing
documented on CCO about just how many spokes you could climb to going that
route.
Nice DMVPN page BTW - dig the drawing...
Regards,
Scott
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
Joseph Brunner
Sent: Thursday, September 13, 2007 2:55 PM
To: 'Scott Vermillion'; sheherezada@gmail.com; 'Cisco certification'
Subject: RE: DMVPN limitation
You need spoke-to-spoke to routing to use EIGRP; the secondary HUB acts like
a spoke too! The real spokes will need to route to that spoke if the HUB is
down.
Or use OSPF, then you don't need to disable split horizon; it just
happens...
-Joe
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
Scott Vermillion
Sent: Thursday, September 13, 2007 4:22 PM
To: sheherezada@gmail.com; 'Cisco certification'
Subject: RE: DMVPN limitation
There might be some spoke-to-spoke implications in the below, but it doesn't
sound like that's a requirement for you (inferring from the terminal
emulator part)...
-----Original Message-----
From: Scott Vermillion [mailto:scott_ccie_list.com@it-ag.com]
Sent: Thursday, September 13, 2007 2:16 PM
To: 'sheherezada@gmail.com'; 'Cisco certification'
Subject: RE: DMVPN limitation
I should have added that even if you don't do the SLB thing, I fail to see
why you couldn't just do perhaps four 3800s at your hub; configure half your
spokes to go to Hubs 1 and 2 and the other half to go to Hubs 3 and 4. I've
not deployed DMVPN on such a large scale, so that's largely just
off-the-top-of-my-head speculation. However, I have deployed a DMVPN
scenario where the spokes needed redundant connectivity to each of two
redundant Head End locations. Thus, four tunnels from each spoke to the
four distinct HE routers (and they were all 3845s). In your case it would
only be two tunnels at any given spoke...
-----Original Message-----
From: Scott Vermillion [mailto:scott_ccie_list.com@it-ag.com]
Sent: Thursday, September 13, 2007 2:03 PM
To: 'sheherezada@gmail.com'; 'Cisco certification'
Subject: RE: DMVPN limitation
Check out "Large-Scale DMVPN" in this link, I think you'll find it
helpful...
http://www.cisco.com/en/US/products/ps6658/products_ios_protocol_option_home
.html
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
sheherezada@gmail.com
Sent: Thursday, September 13, 2007 1:46 PM
To: Cisco certification
Subject: OT: DMVPN limitation
Hi,
Sorry for this off topic, but maybe some of you can redirect me to an
useful resource.
I am planning to deploy from scratch a DMVPN setup and want to
understand the limitations regarding the number of tunnels.
In short:
- 500 spokes - Cisco 877, no physical backup circuits
- 2 hubs, daisy chaining. Basically, I want to ensure that a hub is
always available.
- 3-4 Mbps aggregate bandwidth (that's right, each spoke user has only
a terminal emulator, so it's low bandwidth consumption)
I am planning to use Cisco 3845 for the hubs, but as far as I can read
on the Internet, even a Cisco 7200 with NPE-G1 is limited to 350 DMVPN
tunnels?! Is this because of CPU usage when a major re-convergence
occurs or something else relative to EIGRP? I can't imagine using a
larger box only for several megabits of traffic...
Thanks,
Mihai Dumitru
CCIE #16616 (SP, R&S)
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