Hello Saquib,

I needed some time to prepare an answer.

Your initial requirements were:

>>>() To send all traffic initiated from HQ to AC1 via tunnel 33, if Tunnel 33 is down then send traffic via Tunnel 20 and Tunnel 22

>>>() To send all traffic initiated from HQ to AB1 via Tunnel 20 and Tunnel 22 if both tunnels are down then send via Tunnel 33

Examining the topology diagram we see:

tunnels 20 and 22 connect HQ VPN routers to AB1 VPN router

tunnel 33 connects HQ router HQ_VPN_R1 ro AC1 VPN router

An important element to be considered is the OSPF link between BB_AC1 and BB_AB1 routers that interconnect the two remote sites making internal routes of site AC known in OSPF on site AB and viceversa.

This means that on all GRE tunnels all the IP subnets of site AC and of site AB are advertised.

To implement the desired hierarchy of routing different metrics have to be associated to different subset of routes on the different tunnels.

More specifically, IP subnets and aggregate routes within AC1 address space 172.31.120.0/21 have to be seen with the best metric via tunnel 33.
The same routes have to be received on tunnel 20 or tunnel 22 but with an higher metric (equal on both tunnel 20 and tunnel 22 to perform load sharing when tu33 is down).

The same reasoning reversed applies to the ip address space of AB site 172.31.65.0/21 again IP subnets and aggregate routes within 172.31.65.0/21 have to be advertised with a lower equal metric on AB1 router out of tunnel 20 and tunnel 22.
AC1 router for the same routes within 172.31.65.0/21 has to advertise an higher metric.

Looking at the current configuration as you have reported in penultimate post:

within router eigrp process you would need to set a seed metric to see OSPF routes injected in EIGRP domain.

There are two ways to create a differentiation of EIGRP metrics advertised over the GRE tunnels:

a) use of a route-map to be invoked as additional option in router eigrp process

b) use of offset-lists that add delay selectively to some IP prefixes.

I give below an example of method a)

AC1 router:

ip prefix-list AC1routes seq 5 permit 172.31.120.0/21 le 32

route-map OSPFtoEIGRP_AC1 permit 10
match ip address prefix  AC1routes
set metric 10000 1000 255 1 1500
route-map OSPFtoEIGRP_AC1 permit 20
set metric 1000 20000 255 1 1500

the route-map sets a lower seed metric for local routes and an higher seed metric for routes that are actually of site AB1.

router eigrp 2
redistribute ospf 5 route-map OSPFtoEIGRP_AC1

A similar approach can be used on AB1 router

ip prefix-list AB1routes seq 5 permit 172.31.65.0/21 le 32

route-map OSPFtoEIGRP_AB1 permit 10
match ip address prefix  AB1routes
set metric 10000 1000 255 1 1500
route-map OSPFtoEIGRP_AC1 permit 20
set metric 1000 20000 255 1 1500

the route-map sets a lower seed metric for local routes and an higher seed metric for routes that are actually of site AB1.

router eigrp 2
redistribute ospf 5 route-map OSPFtoEIGRP_AB1

This should give you the desired routing behaviour

set metric for EIGRP uses 5 parameters

BW delay reliability load MTU

EIGRP metric is proportional to delay and inversely proportional to lowest BW on path.

Hope to help
Giuseppe

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