EIGRP Routing across MPLS Cloud

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Aug 10th, 2010
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I appologize if this has been covered but I dont see any exact hits...


We are working with our Service Provider to implement MPLS between our remote sites and main campus. We are currently using PtoP T1 in a hub and spoke model. We are running EIGRP in our entire environment.


We would like to continue to run EIGRP in our environment but the SP does not support this protocol through the cloud. I would prefer not to introduce any new routing protocols into our environment such as BGP. (I believe SP is running BGP).


I have read snippits that I can us e GRE tunnel between sites and send EIGRP routing updates via this tunnel.


Can anyone support this method or are there better alternatives? If I implement GRE, I will still need to configure static routes so GRE knows how to reach the remote sites. I also cannot find any literature on how to configure GRE tunnels and use them ONLY for routing updates. I would think sending all traffic via GRE would cause additional overhead.


I will also have a need to send Multicast traffic between sites. I have read that GRE is the way to do this. To me it seems GRE will serve dual purposes.. first to allowing Dynamic routing updates between sites and also to allow Multicast traffic.


I appreciate any comments or suggestions!

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Chetan Kumar Ress Tue, 08/10/2010 - 08:31
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Hi Phil


Yes, You can use GRE tunnel in your network to run EIRGP routing protocol for all location or to reduce overhead you can have M-GRE tunnel in place of GRE.


It will you over head & number of GRE tunnels.


And you should have static route in every locaiton to reach the destination tunnel address . ( you can have static route or default static route )


the belwo link shoe how to configure DMVPN with EIGRP


https://www.cisco.com/en/US/tech/tk583/tk372/technologies_configuration_example09186a008014bcd7.shtml


In above link if you dont' want to use IP-Sec then don't configure IP-Sec.


Or if you want you can have Multiple point-to-point tunnel & then you can run eigrp but again it will increace the overhead & make you to configure multiple tunnels.


Regards

Chetan Kumar

http://chetanress.blogspot.com

Giuseppe Larosa Tue, 08/10/2010 - 11:49
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Hello Phil,

using GRE tunnels to build an overlay would deny one of the greatest benefits of MPLS L3 VPN: the peer model where each CE talks only with local PE node.


unless you have a small number of sites this approach is not recommended.

What if a new site is added in the future? you would need to configure a tunnel GRE to the new site in each of the existing sites.

You could run a DMVPN  ( that is to use mGRE) to solve this but it has some complexity.


You can run BGP without using mutual redistribution: BGP allows to advertise internal networks using the network command even if they are not directly connected to the CE router but learned via EIGRP.


So it is enough to redistribute only BGP into EIGRP by setting a default seed metric (it requires five values in EIGRP and it is necessary or redistribution will not occur)


router bgp 65001

neigh PE-address remote-as SP-AS-number


network 10.10.10.0 mask 255.255.255.0

network 10.10.20.0 mask 255.255.254.0

no auto-summary


! note:if auto-summary is disabled you need to provide the exact mask / prefix length


router eigrp 100

redistribute bgp 65001

default-metric 10000 1000 255 1 1500

!



! BW delay reliabilty load MTU


Hope to help

Giuseppe

phil.wightman Wed, 08/11/2010 - 07:46
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Thank you both very much for your replies.


I did research the DMVPN and eGRE options and this certainly looks like the solution I am looking for. The NHRP protocol will save me from having to manage all static routes in my environment as well.


I may be running Real Time traffic such as Audio or Video across these circuits through the cloud. I have been told that running GRE will add additional delay to RTP traffic and will affect the quality of the call.  Have either of you run RTP with GRE enabled? Have you noticed any reduction in quality? Is it possible to run the RTP traffic outside the GRE tunnel and only use GRE for the EIGRP routing advertisements?


I am also looking into using BGP, waiting for the service provider to get back with me on that solution.


Thank you again!


Phil

Giuseppe Larosa Sun, 08/15/2010 - 07:22
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Hello Phil,


>>  I have been told that running GRE will add additional delay to RTP traffic and will affect the quality of the call.


with appropriate QoS settings carrying VOIP packets over GRE is not a problem at all


For example we have been able to carry VOIP packets over GRE over IPSec over a satellite link and to use VOIP phones on it!


There are sections of QoS guides and DMVPN design guides about QoS


http://www.cisco.com/en/US/docs/solutions/Enterprise/WAN_and_MAN/DMVPDG.html


http://www.cisco.com/en/US/docs/solutions/Enterprise/Branch/EnBrOver.html


http://www.cisco.com/en/US/docs/solutions/Enterprise/WAN_and_MAN/QoS_SRND/IPSecQoS.html



Hope to help

Giuseppe

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