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Redistributing statics into EIGRP for backup path

mbroberson1
Level 3
Level 3

(see the attached network diagram)

Senario:

You're network is connected to a vendor's network. You have a primary and secondary link to the vendor network. The secondary link is connected to the vendor network through your secondary site. You are running EIGRP for your main network (primary and secondary locations). You would like to inject static routes to the networks you need to access in the vendor's network. You are thinking about also using a floating static on your primary and secondary routers connected to the vendor.

Any suggestions for the best approach?

Thanks

1 Accepted Solution

Accepted Solutions

Brandon

I think we still may be talking at cross purposes.

If you use floating statics on the secondary router the routes will NEVER be used unless the primary fails. An example -

Primary router

==============

ip route 160.20.40.0 255.255.255.0 10.99.0.68

Secondary router

================

ip route 160.20.40.0 255.255.255.0 10.99.0.68 250 <--- Notice the 250 here - this is the AD (Adminstrative Distance)

On both routers you add this under your eigrp config

router eigrp 1

redistribute static

So why don't you need metric's ?

The primary router redistributes the above static into EIGRP. When a route is redistributed into EIGRP it gets an AD of 170.

So the secondary router receives a route from the primary for 160.20.40.0/24 with an AD of 170. It also has a locally configured static route with an AD of 250. So it uses the route received from the primary router. It's own locally configured static is not used, not installed in the routing table and therefore never redistributed.

So the secondary router only has one route to 160.20.40.0/24 and that is via the primary router.

So this is why you don't need metrics because the only active route for 160.20.40.0/24 is via the primary router.

If the primary router fails then it stops advertising the 160.20.40.0/24 network. Because the secondary router no longer receives the route it now uses it's locally configured static to 160.20.40.0/24 which has an AD of 250. It's installs this in it's routing table and then redistributes it into EIGRP. So now all devices in your LAN see the path to that network via your secondary router.

If the primary router comes back up it's static route will be used again because it has a better AD.

Does this make sense ? Is this not what you tested in your lab ?

Jon

View solution in original post

53 Replies 53

Jon Marshall
Hall of Fame
Hall of Fame

Brandon

There are a number of ways to do this. Just to clarify

1) You are looking to add static routes for vendor networks to primary router and secondary router ?

2) if 1) is correct are you then proposing to redistribute these statics into EIGRP ?

3) Where does the idea of using floating statics come in ? - is that for use on the secondary router.

4) Do you need all L3 devices within your network to see the primary router as the way to go to the vendor network ie. is it just the L3 switches or is the L3 switches and the backup router ?

Jon

Hi Jon,

Thanks for your reply.

1) I am looking at adding static routes on the primary and secondary router ( to redistribute into EIGRP with a route-map and tag) to access the networks in the vendor's network.

2) Yes proposing to redistribute into EIGRP.

3) Not really sure, I am up for suggestions on this, but yes initially for use on the secondary router.

4) I think I would like to use the primary router for the path first from both the L3 switches and the backup router, but I am also up for suggestions on this.

I have a home lab I can lab-up the senario this evening if you have some suggestions to try.

Thanks,

Brandon

Brandon

If you want to have all the devices use the primary router then i would suggest

1) Configure statics on primary router eg.

ip route 160.20.54.0 255.255.255.0 50.50.50.2

2) COnfigure statics on secondary router but use an AD of > 170 ie.

ip route 160.20.54.0 255.255.255.0 50.50.50.6 250

3) Then under each eigrp config on both primary and secondary routers

router eigrp

redistribute static

What should happen is that the primary router redistributes it's statics into EIGRP. The secondary router receives them and because the AD of external EIGRP routes is 170 this AD is less than 250 floating statics. So it uses the primary router routes.

If the primary router goes down then it will stop advertising the statics, the secondary router should then use it's floating statics and redistribute these into EIGRP.

Jon

Hi Jon,

I'll try this this evening. So no real need to use a route-map to inject (redistribute)the statics into EIGRP? I guess if I did use a route-map it would essentially be the same, but without the redistribute static under the EIGRP process, huh?

Thanks,

Brandon

Brandon

You may want to use a route-map if you are looking to tag routes or limit which statics you want redistributing.

Jon

Jon,

Attached is a config for the primary and secondary routers. Please feel free to shoot holes at it.;-)

Thanks,

Brandon

Brandon

I'm a bit confused. Could you explain what you are trying to as this is not what we werer talking about, which is fine, but i just need to understand how this will work.

Jon

disregard

Hi Jon,

You can see the configs that would be on the primary and seconday routers.

We are taking the following routes (to the vendor network) and re-distributing them into EIGRP. Is the config not accurate?

ip route 160.20.50.0 255.255.255.0 50.50.50.8

ip route 160.20.40.0 255.255.255.0 50.50.50.8

ip route 160.20.30.0 255.255.240.0 50.50.50.8

ip route 160.20.20.0 255.255.240.0 50.50.50.8

Thanks,

Brandon

Bradon

I can't see 50.50.50.8 on your jpg. The 2 routes to the vendor network on your jpg are

primary -> 50.50.50.2

secondary -> 50.50.50.6

what am i missing :-)

Jon

Oh, Let me see if I am leaving something out.

Thanks

Jon,

I left some stuff off. See if this diagram makes sense?

Thanks,

Brandon

Brandon

Can you have a quick read of the posts between myself and Richard. It's unclear how far EIGRP extends ie. is it running between your primary router and the vendor business router and likewise for the secondary router.

Also it looks like you are using a next hop that is not connected to either of your routers ie. 50.50.50.8 is not on either vendor/business router ? So how would your routers know how to get to that address ?

Sorry for all the questions but we need to understand fully before we can give you an answer.

Jon

Brandon,

If you are running EIGRP then why redistribute routes within EIGRP? Shouldn't the routes already redistribute automatically by DUAL? If I understand what you are wanting, you want your primary route outside your network for all users (at primary site and secondary site) to be through your primary router (10.10.10.1). You also want there to be a feasible successor to the outside through your secondary router (10.20.1.1). The advantage of this will allow no outage experienced by the user when the primary site goes down (EIGRP doesn't take the route in to active because there is a FS). Is that correct?

Richard

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