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EIGRP between routers and making one router preferred

4507 = Louisville core (192.168.187.1)

2851 = Louisville MPLS (192.168.187.252)

3660 = Louisville Point-to-Point (192.168.187.254)

2821 = Lexington MPLS (192.168.13.1)

3640 = Lexington Point-to-Point (192.168.13.3)

The MPLS connection is the primary connection. The Point-to-Point is the backup connection.

I have EIGRP 101 running on every single router, and BGP only running on the MPLS routers between cities.

The 4507 has both the 2851 and the 3660 plugged into it.

If I add a network to the 4507, both of the routers should say something like 'D 10.110.115.0/24 [90/3072] via 192.168.187.1' correct?

The problem I am receiving is that when I add a network to the 4507 router and do a 'sh ip route' on the 2851, the route says it's reachable via the MPLS. It is not saying it's connected to the 4507. It's actually going from the 2851 to the 2821, to 3640, to 3660, then to 4507.

How do i stop this loop? I would like to do this without setting a static ip route.

Also, If i unplug the 3660 and add the network, the 2851 finds the advertised route from the 4507 with no problems. When I plug the 3660 back in, the route starts going back to saying its reachable via the MPLS connection.

Any help or ideas are greatly appreciated.

Thanks

3 ACCEPTED SOLUTIONS

Accepted Solutions
Hall of Fame Guru

Re: EIGRP between routers and making one router preferred

Sorry no visio. Could you save as jpeg.

Anyway, initial observations. There is no control over what is being advertised out from Lexington. if you look you can see Frankfurt and a couple of the Covington/Cincinnati being advertised out. This is because EIGRP is being redistributed into BGP.

If you are absolutely sure you only want to advertise out the 2 subnets from Lexington

Lexington 2821

router bgp 64803

no redistribute eigrp 101 metric 0

network 192.168.13.0 mask 255.255.255.0

network 192.168.253.0 mask 255.255.255.0

That should fix issue 1. So Louisville 2851 should now see 4500 as next-hop for any new subnets you add to Louisville 4500.

Note to see the effects you will need to do a

"clear ip bgp 64.129.251.77 soft out" on the Lexington 2821.

I suggest we just make that change tonight and you can then check to see if all connectivity from all sites is working as it should be and that if you add a new subnet to the 4500 the Louisville 2851 gets the right next-hop.

If that goes okay we can then look at the backup link. I'll wait until i get the visio but i suspect that traffic is not routing how you want it to ie. if Lexington is advertising out Frankfurt that must mean it receives Frankfurt routes via EIGRP. It can only get these via the backup link with Louisville. So i wouldn't be surprised that from an internal switch/router in Lexington ie. not the 2821 if you did a traceroute to Frankfurt it went via Louisville backup link rather than MPLS cloud.

Does this sound okay to you ? The easiest change should be the one to the Lexington router as above.

The backup stuff will be more complicated. I may be asking you to do a few traceroutes and you may decide to wait until Lexington is readdressed.

Let me know what you want to do.

Jon

View solution in original post

Hall of Fame Guru

Re: EIGRP between routers and making one router preferred

"But that route still isn't being advertised over the MPLS"

D 209.Public.222.0/24 [90/28416] via 192.168.13.253, 2w1d, GigabitEthernet0/0

This is the route in your routing table but you are trying to advertise with 209.PUBLIC.224.64 255.255.255.224

change

router bgp 64803

network 209.PUBLIC.222.64 mask 255.255.255.224

to

router bgp 64803

network 209.PUBLIC.222.0 mask 255.255.255.0

I suspect this is the issue with the 10.110.x.x network as well. There must be an EXACT match in the routing table. So do a "sh ip route" on the 2851 and find the network you want to advertise and make sure the BGP network statement matches it eg.

if 10.110.0.0 has a subnet mask of 255.255.255.0 then your BGP statement needs to read

router bgp 64803

network 10.110.0.0 mask 255.255.255.0

Jon

View solution in original post

Hall of Fame Guru

Re: EIGRP between routers and making one router preferred

Kenny

"I tried adding

ip route 10.120.0.0 255.255.0.0 192.168.187.252

ip route 10.120.0.0 255.255.0.0 192.168.113.2

and still didn't have any effect on the Core router"

Is the network you are trying to advertise 10.120.201.0/24 ?

If so you need to add that exact route onto Louisville P2P. Because a router will always choose the most specific route. So Louisville P2P gets an advertisement from Lexington P2P for 10.120.201.0/24 but you have added statics for 10.120.0.0/16 so Louisville P2P will use the 10.120.201.0/24 route.

Try adding to Louisville P2P

ip route 10.120.201.0 255.255.255.0 192.168.187.252

ip route 10.120.201.0 255.255.255.0 192.168.113.2

Jon

View solution in original post

51 REPLIES 51
Hall of Fame Guru

Re: EIGRP between routers and making one router preferred

Is the Louisville P2P connected to Lexington. And if so are you redistributing EIGRP into BGP.

If so then this won't work because Lexington receives a route via the P2P from Lousiville and then advertises this into BGP. BGP is a better metric on the 2851 - AD 20 compared to EIGRP received from the 4507 - AD 90.

So you need to filter which routes are advertised back into BGP at either site. Make sure only the sites internal routes are advertised into BGP.

However if you are doing this then you have another problem. The sites will use the backup link for normal communication. You redistribute BGP into EIGRP but these then become AD 170 and at the same time the site is receiving AD 90 routes down the backup link.

If your subnets within each site are summarisable make the backup link EIGRP passive and use static routes on each backup router.

If the original assumption about the P2P connection is wrong then just ignore all that :-)

Jon

Re: EIGRP between routers and making one router preferred

Jon thanks for your response.

Yes the Lexington router is connected to the Louisville router.

I am redistributing BGP into EIGRP.

Attached is a network topology with all the routing protocols. in jpg form ;)

If you can explain how to filter routes to each site that would be a big help. (That is if the topology matches what you are trying to help me accomplish). And can you explain the different between having the 'no auto-summary' command and not. When I came into this network all the routers were configured with 'no auto-summary'

Thanks!

Highlighted

Re: EIGRP between routers and making one router preferred

Jon (or anyone for that matter) can you explain to me how you would filter the route?

I understand that from the 2821, I want to allow only network 192.168.13.0, and deny all others coming from EIGRP to be distributed through BGP.

Also with the current config, what do i need to remove to clean it up?

Thanks and it's much appreciated. Current config is attached on the updated topology jpg.

Hall of Fame Guru

Re: EIGRP between routers and making one router preferred

Kendrik

Can you confirm whether or not you are redistributing EIGRP back into BGP because i think that is what both Giuseppe and i assumed but your topology map doesn't seem to mention this ?

Jon

Re: EIGRP between routers and making one router preferred

Jon,

the current configuration looks like this on the 2821:

router eigrp 101

redistribute connected

redistribute static

redistribute bgp 64803 metric 100000 10 255 1 1500

network 192.168.13.0

no auto-summary

!

router bgp 64803

no synchronization

bgp log-neighbor-changes

network 64.129.251.76 mask 255.255.255.252

network 192.168.13.0

redistribute static

redistribute eigrp 101 metric 0

neighbor 64.129.251.77 remote-as 4323

default-information originate

no auto-summary

!

ip forward-protocol nd

ip route 0.0.0.0 0.0.0.0 192.168.13.253

ip route 192.168.253.0 255.255.255.0 192.168.13.253

So it looks like yes, I am redistributing on both EIGRP and BGP on the 2821. Is this incorrect? As I said before, this was all setup when I arrived here, so I never originally set it up this way.

thanks again for your response and help

Hall of Fame Guru

Re: EIGRP between routers and making one router preferred

Kendrik

Not necessarily but this is one of your 2 problems.

Problem 1

EIGRP is exchanged via the backup routers so Lexington receives Louisville internal subnets via the backup link. Lexington then redistributes those into BGP. Lexington then advertise those routes back to Louisville via BGP. Louisville 2851 picks the route from Lexington because AD 20 (BGP) < AD 90 (EIGRP).

So to stop that either

1) redistribute EIGRP at each site but add filter so only that sites subnets are advertised

OR

2) Don't redistribute EIGRP into BGP, use network statements under your BGP config. Note that for the network to be advertised it must be in the IGP routing table but each sites networks should be in the routing tables anyway.

I prefer option 2 to be honest but it does mean that if you add another subnet to a site you must remember to add it under the BGP config as well. With option 1 if you add a new subnet it is automatically advertised out.

Your choice. If you choose option 1 then let me know and we can look to filter routes.

Problem 2

When Louisville 2851 receives BGP routes for Lexington subnets it redistributes these into EIGRP. Now we know Louisville 2851 will use BGP to get to these subnets but look at it from Louisville 4500 switch. It receives the routes for Lexington subnets from 2 places

i) Louisville 2851 from BGP redistributed into EIGRP - these will have AD of 170

ii) Louisville 3660 because it is peering with EIGRP to Lexington 3640. These will have AD of 90 so if you do a traceroute from Louisville 4500 to Lexington subnet on it will probably go via the backup link.

So to stop that

1) Use Giuseppe's idea of summary routes on the interfaces of the 3640 and 3660 that connect to each other.

But trouble is if you can't summarise then this becomes more difficult. You could make the link passive, add statics, redistribute into EIGRP and add offsets but that is a bit of a nightmare.

Can you efficiently summarise between sites ?

Jon

Re: EIGRP between routers and making one router preferred

you're the Pro, so let's go with option 2.

Adding a new subnet to BGP seems like something I can remember ;)

So on the 2821 I need to remove the 'redistrubute eigrp 101' from BGP 64803, correct?

The 2851 is not redistributing EIGRP 101.

Additionally, on the 3640 and the 3660, I want to remove the statement that says 'no auto-summary' on EIGRP 101. Is that correct? How do you configure summary routes on just the interface?

Sorry if i'm asking to many questions. I just want to be 100% clear on what I'm about to do. Thanks!

Hall of Fame Guru

Re: EIGRP between routers and making one router preferred

Kendrik

1) "So on the 2821 I need to remove the 'redistrubute eigrp 101' from BGP 64803, correct? "

Yes you do but you need to be careful of doing this within core hours. Basically you need to do the following

Work out the Lexington subnets you need to advertise to Louisville. For each of the subnets add under your BGP config

router bgp 64803

network x.x.x.x mask x.x.x.x (the mask is optional but i always add it)

BUT key thing here is for BGP to advertise this out there must be a match in the IGP routing table on the 2821. So if you add

network 192.168.13.0 mask 255.255.255.0

when you do a "sh ip route" on the 2821 there must be a matching route. This route will be installed via EIGRP.

2) Removing the auto-summary probably won't work because that just determines whether you summarise on classful boundaries or not. You may need to use the "ip eigrp summary-address x.x.x.x" interface command.

Can you provide me with a full list of

Louisville subnets

Lexington subnets

The subnets you provide should be the ones you want to advertise between the sites.

"Sorry if i'm asking to many questions. I just want to be 100% clear on what I'm about to do. Thanks"

Totally understandable, this is your production network after all. You should probably look to do these changes out of core hours.

Jon

Re: EIGRP between routers and making one router preferred

Just to let you know, we are in the midst of changing from 192.168./24 to the 10./24 network so there is a bunch of stuff. It's what also made me realize this problem.

Lexington:

192.168.13.0

192.168.253.0

192.168.113.0 <- this is only used between the 3640 and the 3660 to communicate. so probably shouldn't be in BGP if i'm not mistaken

(Lexington will eventually be on the 10.120.0.0/24 network)

Louisville:

192.168.15.0

192.168.32.0

192.168.33.0

192.168.34.0

192.168.35.0

192.168.36.0

192.168.50.0

192.168.52.0

192.168.187.0

192.168.199.0

10.110.115.0

10.110.132.0

10.110.133.0

10.110.134.0

10.110.135.0

10.110.136.0

10.110.201.1

10.110.213.0

(Louisville will eventually be on the 10.110.0.0/24 network)

And I will try the changes you give me out tonight. thanks again!

Hall of Fame Guru

Re: EIGRP between routers and making one router preferred

Okay, the problem you have is that 192.168.13.0 is in Lexington but 192.168.15.0 is in Louisville - this makes it hard to summarise.

Once you go to 10.120.0.0/24 for Lexington this would be relatively easy.

Sorry to have to ask yet another question - apart from Lexington and Louisville do you have other sites and if so do they use either 192.168.x.x or 10.110.x.x ?

Jon

Re: EIGRP between routers and making one router preferred

Ask all the questions you want and i'll try my best to answer

I have a total of 5 cities.

Cincinnati and Covington are the same situation as Lexington. Both sites have a 2821 router with a MPLS connection. Cincinnati has a 2620 router with a Point-to-Point connected to Louisville 3660. Covington has a 2612 Router with a Point-to-Point connected to Louisville 3660.

Frankfort only has a 2801 router with a point-to-point connection to Louisville 3660

Cincinnati:

192.168.28.0/24

192.168.128.0/24 (only used for communication between the Point-to-Point routers)

Covington:

192.168.18.0/24

192.168.118.0/24 (only used for communication between the Point-to-Point routers)

Frankfort (NO MPLS, only Point-to-Point):

10.150.2.0/24

10.150.5.0/24 (used for Point-to-Point communication)

10.150.10.0/24

10.150.110.0/24

10.150.201.0/24

10.150.213.0/24

Hall of Fame Guru

Re: EIGRP between routers and making one router preferred

Okay, we probably need to take a step back here. Looking at the topology map you have some statics on the 3660 and 3640 routers that are doing something - just not sure what yet :-). Are they meant to be there ?

It would help if the topology map was updated to show all next-hop IP addresses ie. where they are within your network eg.

on the 3660

ip route 0.0.0.0 0.0.0.0 192.168.187.1

where is 192.168.187.1.

What i am really wary of is breaking your network by making changes without the full picture. So lets address the 2 issues separately.

Issue 1 - Lousiville 2851 picking wrong route.

1) On the 2821 Lexington router can you run

"sh ip bgp neigh 64.129.251.57 advertised routes"

and post output.

2) On 2821 Lexington router can you

"sh ip route" and post output

3) Are there any networks that you want to advertise into MPLS from Lexington that you didn't include when i asked about the networks being advertised to Louisville.

Key thing to understand here is that if we remove eigrp redistribution into BGP on Lexington we are only proposing to advertise out

192.168.13.0

192.168.253.0

which is fine for Louisville but do any of your other sites need to receive additional subnet advertisements from Lexington. Because if there are additional subnets from Lexington then we will need to add these in with network statements under BGP as well.

If we can sort the above out then we have solved initial issue with Louisville 2851 picking wrong route.

Issue 2 - backup link.

Looking at the statics it suggests someone has tried to address this before altho i can't say that for sure without knowing where all the next hops are.

Can you do a tracroute to an address in the 192.168.13.x subnet from the Louisville 4500 and tell me which way it goes ie. via MPLS or via the backup link.

Jon

Re: EIGRP between routers and making one router preferred

1. I think you meant 64.129.251.77, because 57 was 'No such neighbor or address family'

LEX-GDM-TWC-MPLS#sh ip bgp neigh 64.129.251.77 advertised

BGP table version is 6825, local router ID is 192.168.13.254

Network Next Hop Metric LocPrf Weight Path

*> 0.0.0.0 192.168.13.253 0 32768 ?

*> 10.110.2.0/24 192.168.13.3 0 32768 ?

*> 10.110.5.0/24 192.168.13.3 0 32768 ?

*> 10.110.100.0/24 192.168.13.3 0 32768 ?

*> 10.110.101.0/24 192.168.13.3 0 32768 ?

*> 10.110.115.0/24 192.168.13.3 0 32768 ?

*> 10.110.132.0/24 192.168.13.3 0 32768 ?

*> 10.110.133.0/24 192.168.13.3 0 32768 ?

*> 10.110.201.0/24 192.168.13.3 0 32768 ?

*> 10.110.213.0/24 192.168.13.3 0 32768 ?

*> 10.150.2.0/24 192.168.13.3 0 32768 ?

*> 10.150.5.0/24 192.168.13.3 0 32768 ?

*> 10.150.10.0/24 192.168.13.3 0 32768 ?

*> 10.150.100.0/24 192.168.13.3 0 32768 ?

*> 10.150.110.0/24 192.168.13.3 0 32768 ?

*> 10.150.201.0/24 192.168.13.3 0 32768 ?

*> 10.150.213.0/24 192.168.13.3 0 32768 ?

*> 64.129.251.76/30 0.0.0.0 0 32768 i

*> 192.168.13.0 0.0.0.0 0 32768 i

*> 192.168.53.0 192.168.13.3 0 32768 ?

*> 192.168.113.0 192.168.13.3 0 32768 ?

*> 192.168.118.0 192.168.13.3 0 32768 ?

*> 192.168.128.0 192.168.13.3 0 32768 ?

*> 192.168.253.0 192.168.13.253 0 32768 ?

*> 209.Public.222.0 192.168.13.253 0 32768 ?

Total number of prefixes 25

2) NEXT POST. TOO MANY CHARACTERS

3) you're correct. for now we only want to advertise those 2 subnets from Lexington.

4)GDM-4507R#traceroute 192.168.13.57

Type escape sequence to abort.

Tracing the route to lexex1.greenebaum.com (192.168.13.57)

1 192.168.187.252 0 msec 0 msec 0 msec

2 64.129.251.57 4 msec 4 msec 0 msec

3 64.129.251.77 4 msec 4 msec 4 msec

4 64.129.251.78 4 msec 0 msec 0 msec

5 lexex1.greenebaum.com (192.168.13.57) 4 msec 4 msec 32 msec

GDM-4507R#

5) attached is the big picture with ALL the routers and configs. do you have visio?

Re: EIGRP between routers and making one router preferred

2)

LEX-GDM-TWC-MPLS#sh ip rou

Codes: C - connected, S - static, R - RIP, M - mobile, B - BGP

D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area

N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2

E1 - OSPF external type 1, E2 - OSPF external type 2

i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2

ia - IS-IS inter area, * - candidate default, U - per-user static route

o - ODR, P - periodic downloaded static route

Gateway of last resort is 192.168.13.253 to network 0.0.0.0

B 192.168.28.0/24 [20/0] via 64.129.251.77, 4w1d

C 192.168.13.0/24 is directly connected, GigabitEthernet0/0

B 192.168.15.0/24 [20/0] via 64.129.251.77, 1d17h

64.0.0.0/30 is subnetted, 4 subnets

B 64.129.251.56 [20/0] via 64.129.251.77, 4w1d

B 64.129.251.60 [20/0] via 64.129.251.77, 4w1d

B 64.129.251.72 [20/0] via 64.129.251.77, 4w1d

C 64.129.251.76 is directly connected, GigabitEthernet0/1

D 192.168.128.0/24 [90/4660480] via 192.168.13.3, 1w2d, GigabitEthernet0/0

B 192.168.198.0/24 [20/0] via 64.129.251.77, 4w1d

10.0.0.0/24 is subnetted, 16 subnets

D 10.110.100.0 [90/4151296] via 192.168.13.3, 1d02h, GigabitEthernet0/0

D 10.110.101.0 [90/4151296] via 192.168.13.3, 1d02h, GigabitEthernet0/0

D 10.110.115.0 [90/4151296] via 192.168.13.3, 1d02h, GigabitEthernet0/0

D 10.150.213.0 [90/4663040] via 192.168.13.3, 5d21h, GigabitEthernet0/0

D 10.150.201.0 [90/4663040] via 192.168.13.3, 1w0d, GigabitEthernet0/0

D 10.110.5.0 [90/4151296] via 192.168.13.3, 1d02h, GigabitEthernet0/0

D 10.110.2.0 [90/4151296] via 192.168.13.3, 1d02h, GigabitEthernet0/0

D 10.150.10.0 [90/4663040] via 192.168.13.3, 1w0d, GigabitEthernet0/0

D 10.150.5.0 [90/4660480] via 192.168.13.3, 1w0d, GigabitEthernet0/0

D 10.150.2.0 [90/4663040] via 192.168.13.3, 1w0d, GigabitEthernet0/0

D 10.110.201.0 [90/4151296] via 192.168.13.3, 1d02h, GigabitEthernet0/0

D 10.110.213.0 [90/4151296] via 192.168.13.3, 1d02h, GigabitEthernet0/0

D 10.110.132.0 [90/4151296] via 192.168.13.3, 1d02h, GigabitEthernet0/0

D 10.110.133.0 [90/4151296] via 192.168.13.3, 1d02h, GigabitEthernet0/0

D 10.150.110.0 [90/4663040] via 192.168.13.3, 1w0d, GigabitEthernet0/0

D 10.150.100.0 [90/4663040] via 192.168.13.3, 1w0d, GigabitEthernet0/0

D 192.168.113.0/24 [90/4148480] via 192.168.13.3, 2w1d, GigabitEthernet0/0

B 192.168.36.0/24 [20/0] via 64.129.251.77, 1d17h

D 192.168.53.0/24 [90/4151296] via 192.168.13.3, 1d17h, GigabitEthernet0/0

B 192.168.52.0/24 [20/0] via 64.129.251.77, 1d17h

B 192.168.187.0/24 [20/0] via 64.129.251.77, 4w1d

B 192.168.34.0/24 [20/0] via 64.129.251.77, 1d17h

B 192.168.50.0/24 [20/0] via 64.129.251.77, 1d17h

B 192.168.35.0/24 [20/0] via 64.129.251.77, 1d17h

D 192.168.118.0/24 [90/4660480] via 192.168.13.3, 2w1d, GigabitEthernet0/0

S 192.168.253.0/24 [1/0] via 192.168.13.253

B 192.168.32.0/24 [20/0] via 64.129.251.77, 1d17h

B 192.168.18.0/24 [20/0] via 64.129.251.77, 4w1d

B 192.168.33.0/24 [20/0] via 64.129.251.77, 1d17h

D 209.Public.222.0/24 [90/28416] via 192.168.13.253, 2w1d, GigabitEthernet0/0

S* 0.0.0.0/0 [1/0] via 192.168.13.253

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