EIGRP via GRE tunnel taking preference

[andrelsilva]

I have a remote site connected via a series of Metro Ethernet links with EIGRP routing configured.

I now created a GRE tunnel over IPSEC over an internet link as a backup path.

MAIN SITE .................................................................................. REMOTE SITE

routerA <-ethernet-> routerB <-ethernet-> routerC <-ethernet-> router1

    |                                                                                                     |

routerX <---------- GRE over IPSEC tunnel ----------------> router2

My problem is when I enable eigrp on the GRE tunnel interfaces it takes over the routes learned over the main path and poises my whole routing, even though the metric is much higher.

The router marks the tunnel bandwidth with a low value and I even increased the delay so this shouldn't happen.

Router2 Tunnel interface configuration:

interface Tunnel10
ip address 172.29.19.133 255.255.255.252
ip mtu 1400
ip tcp adjust-mss 1340
delay 9999900
tunnel source Loopback10
tunnel destination Y.Y.Y.Y

router eigrp 100
 network x.x.x.x

 network z.z.z.z
 redistribute connected
 passive-interface default
 no passive-interface GigabitEthernet0/0/0.10
 no passive-interface GigabitEthernet0/0/0.40
 no passive-interface tunnel10

#sh int tunne10
Tunnel10 is up, line protocol is up
Hardware is Tunnel
Internet address is 172.29.19.133/30
MTU 9976 bytes, BW 100 Kbit/sec, DLY 99999000 usec,
reliability 255/255, txload 1/255, rxload 1/255
Encapsulation TUNNEL, loopback not set
Keepalive not set
Tunnel linestate evaluation up
Tunnel source 172.29.19.129 (Loopback10), destination Y.Y.Y.Y
Tunnel Subblocks:
src-track:
Tunnel10 source tracking subblock associated with Loopback10
Set of tunnels with source Loopback10, 1 member (includes iterators), on interface <OK>
Tunnel protocol/transport GRE/IP
Key disabled, sequencing disabled
Checksumming of packets disabled
Tunnel TTL 255, Fast tunneling enabled
Tunnel transport MTU 1476 bytes
Tunnel transmit bandwidth 8000 (kbps)
Tunnel receive bandwidth 8000 (kbps)

Here's an example of a route on Router2 when EIGRP is disabled on the tunnel, it is pointing to router1 via the lan interfaces, which is correct:

Router2# sh ip route 172.30.40.0
Routing entry for 172.30.40.0/24
Known via "eigrp 100", distance 90, metric 29440, type internal
Redistributing via eigrp 100
Last update from 172.29.14.2 on GigabitEthernet0/0/0.40, 00:00:36 ago
Routing Descriptor Blocks:
* 172.29.14.2, from 172.29.14.2, 00:00:36 ago, via GigabitEthernet0/0/0.40
Route metric is 29440, traffic share count is 1
Total delay is 150 microseconds, minimum bandwidth is 100000 Kbit
Reliability 255/255, minimum MTU 1500 bytes
Loading 1/255, Hops 5
172.29.11.2, from 172.29.11.2, 00:00:36 ago, via GigabitEthernet0/0/0.10
Route metric is 29440, traffic share count is 1
Total delay is 150 microseconds, minimum bandwidth is 100000 Kbit
Reliability 255/255, minimum MTU 1500 bytes
Loading 1/255, Hops 5

When I enable eigrp on the tunnel it takes over even though the distance is the same and the metric is much higher:

Router2# sh ip route 172.30.40.0
Routing entry for 172.30.40.0/24
Known via "eigrp 100", distance 90, metric 2585574912, type internal
Redistributing via eigrp 100
Last update from 172.29.19.134 on Tunnel10, 00:01:08 ago
Routing Descriptor Blocks:
* 172.29.19.134, from 172.29.19.134, 00:01:08 ago, via Tunnel10
Route metric is 2585574912, traffic share count is 1
Total delay is 99999020 microseconds, minimum bandwidth is 100 Kbit
Reliability 255/255, minimum MTU 1400 bytes
Loading 255/255, Hops 2

Any thoughts?

[chrihussey]

Interesting and my compliments on providing all the pertinent information. Could be a bug, but what does the route look like in R1 when the tunnel is up? Also, with the tunnel up, is RA still advertising it to R1?

Thanks

[andrelsilva]

Hi thanks for replying

With the tunnel up R1 learns the routes via R2 and RC from R1.

RA is still announcing and RB is getting them correctly.

RouterA <-eth 1Gbps-> RouterB <-eth 100Mbps-> RouterC <-eth 100Mbps-> Router1

[chrihussey]

I'm leaning towards it being a bug, but could you post the output of "sh ip eigrp topology 172.30.40.0/24" with the tunnel active?

Thanks

[Georg Pauwen]

Hello,

in addition to the other posts, post the full configurations of all six routers so we can lab this...

[Predrag Jovic]

Most likely recursive loop is created since you are advertising tunnel endpoints through tunnel. Route to tunnel endpoint should not point to tunnel (need to point to wan interface). Can be achieved by filtering tunnel endpoints with distribution list, or static route.

[paul driver]

Hello

why don’t you NOT advertise the gre tunnel and just policy route over it the subnets you wish to traverse it

or

create a different eigrp or routing process and advertise it over that?