From: Jason Madsen (madsen.jason@gmail.com)
Date: Sun Jan 11 2009 - 18:44:01 ARST
true nuf. it appears he used area 0 ONLY however and used default GRE
tunnel and OSPF values (ospf cost of 11111) so with his endpoint being only
a couple of hops away, he never should've "preferred" the tunnel for his
endpoints in the first place with or without the distribute list. I'm
willing to be he used GNS3 and it's a gliche or something unless there's
more to his config' that he didnt' post.
Jason
On Sun, Jan 11, 2009 at 12:42 PM, Scott Morris <
smorris@internetworkexpert.com> wrote:
> The rule is that whatever you are using for your destination address needs
> to NOT be preferred through the tunnel.
>
> With that in mind, you look at how you learn the route originally:
>
> 1. If via a different protocol, then you can use things like
> ACL/distribute-lists or even changing the AD (so I don't care if it's
> learned, it won't get used by routing table)
>
> 2. If it's via the same protocol then you need to look differently. Some
> (RIP, EIGRP) it may simply involve changing the metric. Others (like OSPF)
> you have further analysis to look at about whether it's the SAME route you
> are learning (instead of a /24 vs. /32 if loopback) as well as other fun
> things like intra-area vs. inter-area vs. external route.
>
> But once you understand how the router learned/chose the router ORIGINALLY
> (pre-tunnel) and then understand what is changing the tunnel becomes up...
> Compare the two and you should be good.
>
> Cheers,
>
>
>
>
> -----Original Message-----
> From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
> Nitro Drops
> Sent: Sunday, January 11, 2009 8:27 AM
> To: ccielab@groupstudy.com
> Subject: Recursive Routing
>
> Hi All,
>
> Have been trying to fix my recursive routing for OSPF in the last 2 hours.
>
> R1 F0/0 .1 >> 155.1.37.0 >> .2 F0/0 R2 F0/1 .2 >> 155.1.0.0 >> .3 F0/0 R3
>
> GRE tunnel created between R1 and R3
>
> R1
> interface Tunnel0
> ip address 155.1.57.1 255.255.255.0
> tunnel source 155.1.37.1
> tunnel destination 155.1.0.3
>
> router ospf 1
> network 155.1.0.0 0.0.255.255 area 0
> distribute-list 2 in Tunnel0
>
> access-list 2 deny 155.1.0.0 0.0.0.255
> access-list 2 deny 155.1.37.0 0.0.0.255
> access-list 2 permit any
>
>
> R3
> interface Tunnel0
> ip address 155.1.57.3 255.255.255.0
> tunnel source 155.1.0.3
> tunnel destination 155.1.37.1
>
> router ospf 1
> network 155.1.0.0 0.0.255.255 area 0
>
> distribute-list 2 in Tunnel0
>
>
> access-list 2 deny 155.1.0.0 0.0.0.255
>
> access-list 2 deny 155.1.37.0 0.0.0.255
>
> access-list 2 permit any
>
>
> To prevent recursive routing, i have used a distribute-list to prevent
> learning the tunnel destination from the tunnel interface. However, my int
> tunnel keeps on flapping (Debug IP routing as attached), did i missed out
> anything on my configs or did i use the wrong method? I used the same
> method
> on RIP & EIGRP, distribute-list works fine on both of them, distribute-list
> applying in/out to stop the tunnel destination from advertising/learning
> from
> the tunnel interface.
>
> Except on OSPF, i can only prevent the router from learning from the tunnel
> destination, CANT stop advertising the tunnel destination out of the tunnel
> interface, as the OSPF distribute-list only works for inbound.
>
> Cheers
> Nit
>
>
> IP routing debugging is on
> R1#
> *Mar 1 08:54:30.021: %OSPF-5-ADJCHG: Process 1, Nbr 15.2.2.2 on Tunnel0
> from
> LOADING to FULL, Loading Done
> *Mar 1 08:54:41.541: RT: del 155.1.0.0/24 via 155.1.37.2, ospf metric
> [110/120000]
> *Mar 1 08:54:41.545: RT: delete subnet route to 155.1.0.0/24
> *Mar 1 08:54:41.549: RT: NET-RED 155.1.0.0/24
> *Mar 1 08:54:48.869: %LINEPROTO-5-UPDOWN: Line protocol on Interface
> Tunnel0,
> changed state to down
> *Mar 1 08:54:48.881: RT: is_up: Tunnel0 0 state: 4 sub state: 1 line: 0
> has_route: True
> *Mar 1 08:54:48.885: %OSPF-5-ADJCHG: Process 1, Nbr 15.2.2.2 on Tunnel0
> from
> FULL to DOWN, Neighbor Down: Interface down or detached
> *Mar 1 08:54:48.893: RT: interface Tunnel0 removed from routing table
> *Mar 1 08:54:48.893: RT: del 155.1.57.0/24 via 0.0.0.0, connected metric
> [0/0]
> *Mar 1 08:54:48.897: RT: delete subnet route to 155.1.57.0/24
> *Mar 1 08:54:48.901: RT: NET-RED 155.1.57.0/24
> *Mar 1 08:54:51.553: RT: SET_LAST_RDB for 155.1.0.0/24
> NEW rdb: via 155.1.37.2
>
> *Mar 1 08:54:51.561: RT: add 155.1.0.0/24 via 155.1.37.2, ospf metric
> [110/120000]
> *Mar 1 08:54:51.561: RT: NET-RED 155.1.0.0/24
> *Mar 1 08:54:57.869: %LINEPROTO-5-UPDOWN: Line protocol on Interface
> Tunnel0,
> changed state to up
> *Mar 1 08:54:57.881: RT: is_up: Tunnel0 1 state: 4 sub state: 1 line: 0
> has_route: False
> *Mar 1 08:54:57.885: RT: SET_LAST_RDB for 155.1.57.0/24
> NEW rdb: is directly connected
>
> *Mar 1 08:54:57.889: RT: add 155.1.57.0/24 via 0.0.0.0, connected metric
> [0/0]
> *Mar 1 08:54:57.893: RT: NET-RED 155.1.57.0/24
> *Mar 1 08:54:57.897: RT: interface Tunnel0 added to routing table
> *Mar 1 08:54:58.973: %OSPF-5-ADJCHG: Process 1, Nbr 15.2.2.2 on Tunnel0
> from
> LOADING to FULL, Loading Done
> *Mar 1 08:55:11.577: RT: del 155.1.0.0/24 via 155.1.37.2, ospf metric
> [110/120000]
> *Mar 1 08:55:11.581: RT: delete subnet route to 155.1.0.0/24
> *Mar 1 08:55:11.585: RT: NET-RED 155.1.0.0/24
> R1#undebug <http://155.1.0.0/24R1#undebug>
> *Mar 1 08:55:17.901: %OSPF-5-ADJCHG: Process 1, Nbr 15.2.2.2 on Tunnel0
> from
> FULL to DOWN, Neighbor Down: Interface down or detached
> *Mar 1 08:55:18.869: %LINEPROTO-5-UPDOWN: Line protocol on Interface
> Tunnel0,
> changed state to down
> *Mar 1 08:55:18.877: RT: is_up: Tunnel0 0 state: 4 sub state: 1 line: 0
> has_route: True
> *Mar 1 08:55:18.881: RT: interface Tunnel0 removed from routing table
> *Mar 1 08:55:18.885: RT: del 155.1.57.0/24 via 0.0.0.0, connected metric
> [0/0]
> *Mar 1 08:55:18.889: RT: delete subnet route to 155.1.57.0/24
> *Mar 1 08:55:18.889: RT: NET-RED 155.1.57.0/24
> R1#undebug <http://155.1.57.0/24R1#undebug> al
> *Mar 1 08:55:21.589: RT: SET_LAST_RDB for 155.1.0.0/24
> NEW rdb: via 155.1.37.2
>
> *Mar 1 08:55:21.597: RT: add 155.1.0.0/24 via 155.1.37.2, ospf metric
> [110/120000]
> *Mar 1 08:55:21.597: RT: NET-RED 155.1.0.0/24l
> All possible debugging has been turned off
>
>
>
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