Design

[chrisfata]

Hello all,

I have two network designs that I would like you all to look over and let me know what is the better way to go.

Design 1: This design links each office with BGP and OSPF.

Design 2: This design links each office with EIGRP.

When looking at each design, think about all aspects of convergence and how routing will be affected within each design.

Background information:

Each office has an MPLS connection back to the core in Grand Rapids, with a secondary DMVPN over the internet.  The MPLS provider does not support Multicast on the cloud and Multicast is a requirment to the design.  The entire network is Cisco equipment.

The diagrams for the designs are attached.

thank you and kind regards.

[Mohamed Sobair]

Hi,

I will go and view my point directly here with two short answers:

1- Design 1 is Excellent and the best from my point of view. why? because flapping on the OSPF Network doesnt affect the BGP operation overall , although it  doesnt provide rapid convergence similar to Eigrp but we can still tweak the timers to achiev rapid convergence , and you have better control with sustainable stability approach here.

2- Design 2 Is Good, because Eigrp provides rapid convergence , however, flapping on any of the sites effect the whole Eigrp Operation. Besides not to forget about Query messages and reply, it has to be well designed IF So to keep all sites as Stub sites to reduce Eigrp Query Scopes and eleminate flapping to cause excessive Network problems.

However, I would Go with Design 1 for the reason I mentioned, and If I have to , I can go with Design 2 but with more suitable design approach. ie: Applying syub routers , Summarization

HTH

Mohamed

[chrisfata]

Thank you for your input on the design........

For design #2, flapping was taken into account on the EIGRP process and summarization at the network boundries was being done to take care of those issues.

One thing that I am looking at is convergence time between BGP vs. EIGRP.  With EIGRP, a feasible successor routes could be chosen to provide faster convergence than with BGP.  The issue that I am stumbling with on design one is the fact that if the Grand Rapids office looses connectivity to the MPLS, when traffic is sent over the DMVPN link to the remotes those locations will not have an updated route back and will black hole into the MPLS cloud until the providers route is no longer present.  EIGRP will take care of the issue because the remote locations will know instantly that the feasible route is no longer present and will begin using the successor route.

Thoughts?

[Mohamed Sobair]

Hi,

That is indeed true, Eigrp provides rapid convergence in comparison with BGP. and As you mentioned, if your Objective more in speeding convergence, then Eigrp is the way to go. You can even do more with Eigrp variance and (Traffic share min) command, this command wven places the feasible successor route in the routing table, it just take it from Eigrp topology table and put in the routing table for faster convergence. However, As I said , the Only problem would be with flapps and Quieries , So you have to design it Well so that you take all precautions.

HTH

Mohamed

[chrisfata]

Thanks for your input......

Convergence is not the only concern that I have but it is a big one.  Another issue that I am looking at is ease of administration and ease of deployment.  For route determiniation with the EIGRP design, all I would have to do is add delay on the internet facing DMVPN tunnels and the primary route would traverse the MPLS.  With BGP as a solution, the configuration and administration becomes more indepth than that with EIGRP.

You make very valid points and I completely agree that if EIGRP is deployed in this solution, the proper measures must be taken to prevent route instabilities and stuck-in-active issues.

[Mohamed Sobair]

Hi,

Convergence is the main point here, BGP as a routing protocol if you are familiar with is very scalabel and powerful, and its configuration is not at all difficult to manage. (You just need to be familiar with the protocol and its behaviour).

However, Comparing to Eigrp, then I would say yes, Eigrp in terms of config and Administration can be easily managed and deployed rather than with BGP.

Regards,

Mohamed