[c-nsp] EIGRP on mGRE/DMVPN

Steve Housego Steve.Housego at itps.co.uk
Fri Nov 1 10:30:45 EDT 2013


Thanks for the reply Chris,

I've looked, but not made the investment yet, theres loads on there that i want to look at to be honest :)

110% agree dynamic BGP peer groups is the route we should take but the problem is this new router is to support an existing eigrp dmvpn network which has 2x 3825's at the primary Hub site with around 250 eigrp neighbors per mgre per router (only 1 mgre per router),

This new router is to be placed in the DR site location, we dont want to buy 2x routers for the DR site (cost/rack space/power etc..) nor increase the complexity/deployement.

Really just looking for a firm answer on how many eigrp neighbors are supported on a single mgre, and what sorts of issues might present themselves when we push it to circa 500 (i.e. slow re-convergage - we can live with that for DR)

SteveH

________________________________
From: Chris Marget
Sent: 01 November 2013 14:14
To: Steve Housego
Subject: Re: [c-nsp] EIGRP on mGRE/DMVPN

Have you checked out Ivan Pepelnjak's DMVPN webinars? http://www.ipspace.net/DMVPN_trilogy

He get into scaling questions there. We're running BGP for scaling reasons.

/chris


On Fri, Nov 1, 2013 at 8:15 AM, Steve Housego <Steve.Housego at itps.co.uk<mailto:Steve.Housego at itps.co.uk>> wrote:
Hi all,

Has anyone ever put more than 500 eigrp nieghbours over an mGRE(DMVPN) interface? If so on what hardware? Any issues encountered?

Were looking at either a 3845 or an ASR1002, with approximatly 500 neighbors on a single mgre interface but with potental to grow, we want to standardise our config so would prefer one tunnel endpoint.

Based on the DMVPN design guide (see extract below) it suggests well under 500 as a maximum, but is dated in 2008... 5 years later and ASR's are reasonbly priced..


http://www.cisco.com/en/US/docs/solutions/Enterprise/WAN_and_MAN/DMVPN_2_Phase2.html#wp38036

"If the DMVPN subnet is configured with a /24 network prefix, the neighbor count is limited to 254, which is a safe operational limit. Beyond this number, a compromise is required to balance re-convergence with recovery. In very large EIGRP networks, it may be necessary to adjust the EIGRP hold time to allow the hub more time to recover without thrashing. However, the convergence time of the network is delayed. This method has been used in the lab to establish 400 neighbors. "
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Gateshead
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T. 0191 442 8300
D. 01914428300
M.
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