Enabling both of RIP and IGRP.. advantages, disadvantages, Risks

Hello Experts:

What is/are advantages, disadvantages and future risks of enbabling both of RIP and IGRP ??

Thanks in advance.
Saed Salman
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they're easy but no vlsm for one. slower convergence.
Don JohnstonInstructorCommented:
Other than a little extra CPU and bandwidth load, there aren't any real advantages/disadvantages/risks of running both. It's really a question of you need to do.

Do you HAVE to run RIP and IGRP? If you do, then you need to enable both. If you don't then... don't.

Typically, one of the goals in routing is the run one routing protocol. Running multiple routing protocols increases the amount of work for the admin and the complexity of the configuration.

So unless you have to connect with routers running RIP and IGRP, pick a protocol.

I will say however that IGRP is no longer supported on the latest IOS version so there may be some support issues down the road.

And RIP is probably the most primitive of the routing protocols. So unless you have a relatively small network, you may want to consider EIGRP or OSPF.
SaedSalmanAuthor Commented:
Its a question that my instructor asked me, And I need something theoretical,logical and ordered to say tomorrow.
provide me with more details please, I googled about thsi but did not find something useful.

I do know about IGRP and RIP and how they work, But I will not invent a new protocol.
Where does my instructor get his questions from ? Mars ?
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Don JohnstonInstructorCommented:
Sounds like a "book" instructor. Probably found a statement in some book somewhere that stated advantages/disadvantages and risks. Without that book, all you can do is guess.

I hate questions like that.

So here you go:

Industry standard
Been around FOREVER
Every vendor in the world supports it
Two versions (v1 classful and v2 classless)

Distance vector (doesn't scale well)
30 seconds updates
15 hop maximum distance
Metric is hops (no consideration of bandwidth)
Slow convergence

Metric uses bandwidth, delay, reliability and load.
90 second update (less overhead)
no 15 limitation

Cisco proprietary
Distance vector
Slow convergence
classless only
no authentication
No longer available

Running both?

Other than a more complex config and the additional overhead of two protocols, I can't think of any other issues.

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SaedSalmanAuthor Commented:
Thank you very much donjohnston,
but I will not tell him: more complex config and the additional overhead of two protocols.  ONLY

the reset of your post seems as a differentiation between RIP and IGRP.

> +
> no 15 limitation
Yes, you are right, but there is alwayes an upper bound. For IGRP it is 50 :)

I appreciate you efforts, thanks again.
Don JohnstonInstructorCommented:
IGRP has a max hop count of 255. It's set to 100 by default.
probably stupid but
could rip poison a good igrp route?
Don JohnstonInstructorCommented:
No. RIP has an Administrative Distance (AD)of 120 while IGRP is 100.  AD is the deciding factor when you learn the same route through two different protocols.
SaedSalmanAuthor Commented:
I found this:

48.If both RIP and IGRP are enabled on a router, it will always use IGRP, as IGRP has higher precedence. Therefore, when using IGRP, disable RIP in order to spare resources.

Don JohnstonInstructorCommented:
First, it's called "Administrative Distance. Precedence is a completely different issue topic.

Second, if someone is running RIP and IGRP it is probably because they're communicating with a router running RIP and a different router running IGRP. So if you disable RIP and the IGRP router fails, you will have lost the alternate path to the destination.

Unless they're talking about running RIP and IGRP between two routers and that's something that there is absolutely no reason to do.
SaedSalmanAuthor Commented:
My Instructor should answer the question this Sunday, I will post his answer here and take an action ;-)
SaedSalmanAuthor Commented:
Thank you again
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