Redistribute EIGRP into OSPF with different AD based on originating router

[mwilson]

I am trying to redistribute routes from one EIGRP domain with 5 routers to an OSPF domain but keep optimal routing paths.  If I generically redistribute the routes all routes have the same Metrics and any path could be chosen. 

How can I redistribute routes from each router but keep the optimal routing into the next protocol?

Example:

Router A and B are Core routers in EIGRP domain 1111.

Routers C and D are edge routers neighboring with each other and A.

Routers E and F are edge routers neighboring with each other and B.

Routers C,D,E,F Redistribute EIGRP into OSPF. 

Routers in OSPF domain have 4 paths now to Router A and B due to equal metric at redistribution point.

This makes for sub-optimal routing. 

Ideally, I would like traffic to Router A to go through C and D.  Unless of course they are unavailable. Then E and F should take the traffic.  Likewise for Router B using E and F. 

Any advice is greatly appreciated. 

Thank you in advance.

[Julio E. Moisa]

Hi

If you are using the same metric redistributing you could increase the metrics  from the others routers to keep the best patch. Do you have a design?

[mwilson]

[mwilson]

As you can see traffic to 20.20.20.0/24 should ideally go from OSPF router to E or F then B. If E and F are unavailable then they should go to C and D. I cant change the redistribute metrics or I force all traffic to go that direction.

[Julio E. Moisa]

Hi

Im going to provide you a configuration that should work.

ROUTER C (The last path if the rest are unavailable)

router ospf 1
redistribute eigrp 1111 metric 200 subnets

router eigrp 1111
redistribute ospf 1 metric 100000 200 255 1 1500

ROUTER D  (Primary Path if Router E fails)

router ospf 1
redistribute eigrp 1111 metric 100 subnets

router eigrp 1111
redistribute ospf 1 metric 100000 100 255 1 1500

ROUTER E  (Primary Path if Router F fails)

router ospf 1
redistribute eigrp 1111 metric 50 subnets

router eigrp 1111
redistribute ospf 1 metric 100000 50 255 1 1500

ROUTER F  (Primary Path)

router ospf 1
redistribute eigrp 1111 subnets

router eigrp 1111
redistribute ospf 1 metric 100000 10 255 1 1500

Not the delay and metric are decreasing, OSPF and EIGRP will prefer the lowest metrics first. There are many ways to prefer a path over other.  Also this configuration will provide symmetric traffic. 

Hope it is useful

:-)

[mwilson]

Julio,

 Thank you.  But it looks like all your doing is forcing ALL traffic destined to any of the subnets on router A and B through F. 

That is sub optimal if my destination is Router A.  Correct?  Or am I missing something.

Thank you!

[Julio E. Moisa]

Actually no, because router A will prefer the routes through router B (comparing metrics), now you can use route-map and prefix list let me provide an example to fix that. Take in consideration that you have partial mesh, if you want to avoid sub optimal path you could connect router A and B to each edge router. 

[mwilson]

Router A and B are in different physical locations from the other sites edge routers.

[Julio E. Moisa]

Hi

Ok just please let me understand the topology as router A & B are over the same cloud hehehe, Router A should use Router C or D to reach OSPF, right? or router A should reach OSPF via router B and then E or F ?

How are you designing the flow of traffic? If they are going to use the specific edge routers we can use prefix-lists

[mwilson]

Exactly Julio.  With the other side as a backup.

[Julio E. Moisa]

Got it, please let share the config. 

[Julio E. Moisa]

Hi

Here an example when you are redistributing EIGRP into OSPF, something similar should be when you are redistributing OSPF into EIGRP. 

ROUTER C  (Backup to reach Router A's routes and fourth option to reach Router B's subnets from OSPF)

ip prefix-list EIGRP-SUBNETS-ROUTERB seq 5 permit 10.10.10.0/24
ip prefix-list EIGRP-SUBNETS-ROUTERB seq 10 permit 20.20.20.0/24

ip prefix-list EIGRP-SUBNETS-ROUTERA seq 5 permit 30.30.30.0/24
ip prefix-list EIGRP-SUBNETS-ROUTERA seq 10 permit 40.40.40.0/24

route-map EIGRP-TO-OSPF permit 5
match ip address prefix EIGRP-SUBNETS-ROUTERB
set metric type-2
set metric 20

route-map EIGRP-TO-OSPF permit 5
match ip address prefix EIGRP-SUBNETS-ROUTERA
set metric type-1
set metric 20

router ospf 1
redistribute eigrp 1111 route-map EIGRP-TO-OSPF subnet

ROUTER D (Primary to reach Router A's routes and third option to reach Router B's subnets from OSPF)

ip prefix-list EIGRP-SUBNETS-ROUTERB seq 5 permit 10.10.10.0/24
ip prefix-list EIGRP-SUBNETS-ROUTERB seq 10 permit 20.20.20.0/24

ip prefix-list EIGRP-SUBNETS-ROUTERA seq 5 permit 30.30.30.0/24
ip prefix-list EIGRP-SUBNETS-ROUTERA seq 10 permit 40.40.40.0/24

route-map EIGRP-TO-OSPF permit 5
match ip address prefix EIGRP-SUBNETS-ROUTERB
set metric type-2
set metric 10

route-map EIGRP-TO-OSPF permit 5
match ip address prefix EIGRP-SUBNETS-ROUTERA
set metric type-1
set metric 10

router ospf 1
redistribute eigrp 1111 route-map EIGRP-TO-OSPF subnet

ROUTER E  (Backup to reach Router B's routes and fourth option for Router A's subnets  from OSPF)

ip prefix-list EIGRP-SUBNETS-ROUTERB seq 5 permit 10.10.10.0/24
ip prefix-list EIGRP-SUBNETS-ROUTERB seq 10 permit 20.20.20.0/24

ip prefix-list EIGRP-SUBNETS-ROUTERA seq 5 permit 30.30.30.0/24
ip prefix-list EIGRP-SUBNETS-ROUTERA seq 10 permit 40.40.40.0/24

route-map EIGRP-TO-OSPF permit 5
match ip address prefix EIGRP-SUBNETS-ROUTERB
set metric type-1
set metric 20

route-map EIGRP-TO-OSPF permit 5
match ip address prefix EIGRP-SUBNETS-ROUTERA
set metric type-2
set metric 20

router ospf 1
redistribute eigrp 1111 route-map EIGRP-TO-OSPF subnet

ROUTER F  (Primary to reach Router B subnets and third option to reach Router A subnets)

ip prefix-list EIGRP-SUBNETS-ROUTERB seq 5 permit 10.10.10.0/24
ip prefix-list EIGRP-SUBNETS-ROUTERB seq 10 permit 20.20.20.0/24

ip prefix-list EIGRP-SUBNETS-ROUTERA seq 5 permit 30.30.30.0/24
ip prefix-list EIGRP-SUBNETS-ROUTERA seq 10 permit 40.40.40.0/24

route-map EIGRP-TO-OSPF permit 5
match ip address prefix EIGRP-SUBNETS-ROUTERB
set metric type1
set metric 10

route-map EIGRP-TO-OSPF permit 5  
match ip address prefix EIGRP-SUBNETS-ROUTERA
set metric type-2
set metric 10

router ospf 1
redistribute eigrp 1111 route-map EIGRP-TO-OSPF subnet

[paul driver]

Hello

@julio - Mutual redistribution from multiple distribution points, I could be wrong here but It doesn't seem you accounted for the potential of the eigrp routes from being re-introduced back into eigrp as ospf routes.

Maybe matching on the same prefixes but apply tagging to them instead so those redistributed tagged prefixes can be negated from coming back as ospf routes and  would also provide a way to manipulate the preference based on the same tags.

What do you think?

res
Paul

[Julio E. Moisa]

Hi Paul,

Thank you, totally agree that could happens but I suggested use something similar using prefix-list and route-maps on OSPF redistribution into EIGRP or using tags like you mentioned. But I dont see the OSPF prefixes to complete the configuration hehe. 

I prefer redistribute with filtering so you can handle what prefixes are going to be advertised.   

[mwilson]

Paul,

  Thanks for the input.   I agree about the tagging/routing loops from reintroduction of routes that originated from same router.   I've dealt with that using the tags and route maps.  Seems to be good.  My main concern now is that I don't want a manual ACL if I can help it.  I was hoping to use router ID or address but it isn't working.  It doesn't use the originating routers address to filter.  But filters on route source... which is next hop .  Not the actual source. Still hoping for an automated way but haven't found it.  

 Thanks again.