EIGRP Stub with Dual Remote Routers

[alexloh83]

Hi All,

I need some technical help for my network, please find the attached prototype network diagram for your better understanding....

Topology: Hub and spoke

Objective:

1) RouterA02 running in pure standby mode, and only activate when RouterA01 down or RouterA01 tunnel 1 and tunnel 1001 down.

2) RouterA01 got two tunnels, but only tunnel 1 is in use and tunnel 1001 as a backup link.

3) When the both tunnel 1 and tunnel 1001 down for RouterA01, all the traffic (Incoming and Outgoing) should forward/go to RouterA02.

My problem:

I am not sure whether my current configuration is correct or not, so I need your advice to correct me or advice me a best solution for this kind of network setup...thanks.

[Mohamed Sobair]

Hi,

1- remove the default route from Spoke 1, as you already advertises a default route from Eigrp from both Hubs.

2- Increase the delay from Hub 2 advertises Eifrp prefixes in order for the Spokes to take Hub 1 as primary and Hub 2 as a secondary. you can accomplish this by increasing the delay on 2nd tunnel or Offset-list.

This will ensure traffic from the Spokes takes the desired prinmary path.

Other than the above, your config looks Ok and should be fine.

Please come back if you have any other question..

HTH

Mohamed

[alexloh83]

Hi Mohamed,

Because both RouterA01 and RouterA02 are configured as stub, so if I remove the static default route from my RouterA01, if the WAN link down, how can I learn the default route from RouterA02? This is the portion I dont know how to solve it.

[Giuseppe Larosa]

Hello Alex,

from EIGRP command reference

The static keyword permits the EIGRP stub routing feature to send static routes. Without the configuration of this option, EIGRP will not send any static routes, including internal static routes that normally would be automatically redistributed. It will still be necessary to redistribute static routes with the redistribute static command.

http://www.cisco.com/en/US/docs/ios/iproute_eigrp/command/reference/ire_a1.html#wp1039726

Because in your network diagram there is a device A03 connected on the client vlan with a different IP subnet connected to it, you can :

or add the static option to eigrp stub + redistribute static  and you passive internal lan (see note later) and an HSRP group  to be run on internal vlan to provide a default gateway next-hop address for default route on A03 router. HSRP management would require tracking of tunnel interfaces.

OR you can remove the eigrp stub option on the two routers and add EIGRP to third router 1841 (and this can be stub indeed)

I would do in this way, the third router can be configured as EIGRP stub the other two would be far better to be full EIGRP routers.

At the end it is safer and easier:

stub = leaf no device behind and this is not your case on A01 and A02

Note on internal LAN:

In fact, you have activated EIGRP on the lan interface, to really use this path between routers A01 and A02 they have to be non stub.

An EIGRP stub router cannot be a transit between other routers.

That is A01 will not advertise on lan segment what it learns from tunnel interfaces and so would do A02 if both configured as stub.

So if A01 and A02 are stub there is no use on running EIGRP on the LAN interface

to limit query range you can use EIGRP summary routes on tunnel interfaces of core routers.

Hope to help

Giuseppe

[alexloh83]

Hi Giuseppe,

Thanks for your advice, i have come out with a new network diagram with new configuration, can you help to have a look whether it is ok?

Diagram : PrototypeEIGRP2.pdf

[Giuseppe Larosa · Accepted solution]

Hello Alex,

your configuration is now correct.

possible further tuning is to use delay on tunnel interfaces on A02 and core routers to A02 to make tunnels via A01 preferred.

check current delay with

sh interface tunnel

delay is expressed in tens of microseconds

delay ?
  <1-16777215>  Throughput delay (tens of microseconds)

conf t

int tu x

delay 100000

Hope to help

Giuseppe

[alexloh83]

Hi Giuseppe,

Thanks...