From: Jason Morris (mcnever@gmail.com)
Date: Sun Feb 22 2009 - 02:56:11 ARST
something to keep in mind about how ospf distribute lists work
you can never do a distribute list OUT with OSPF.
OSPF filters LSAs from the ospf database to the routing table vs filtering
routes advertised or recieced from a neightbor like eigrp or rip does.
all the databases in an area have to have the same info or ospf can't
calculate paths correctly.
if that makes since.
jason
On Sat, Feb 21, 2009 at 11:35 PM, ALL From_NJ <all.from.nj@gmail.com> wrote:
> Interesting lab testing tonight, was playing w/ tunnel interfaces and OSPF.
>
>
> I had a scenario I was practicing, basically it was:
>
> NBMA w/ network type of non-broadcast. Can not use neighbor command or
> make
> any config changes to the physical interface on either sides.
>
> So I created a tunnel and added it to OSPF.
>
> As you would expect, recursive routing began to occur.
>
> Here is a nifty debug output which quickly showed why the neighbor bounces:
>
> R2#debu ip ospf adj
> OSPF adjacency events debugging is on
>
> *Mar 1 04:34:36.531: %TUN-5-RECURDOWN: Tunnel1 temporarily disabled due to
> recursive routing
> *Mar 1 04:34:37.531: %LINEPROTO-5-UPDOWN: Line protocol on Interface
> Tunnel1, changed state to down
> *Mar 1 04:34:37.531: OSPF: Interface Tunnel1 going Down
>
> I know one answer to solve this is to simply remove the physical link's
> network address from OSPF. Odd learning though, as I tried to configure
> other method of filters.
>
> OSPF would not take a distribute list OUT for the tunnel interface ...
> figured I would simply keep the local physical link's network from being
> advertised out via the tunnel. No-go on this.
>
> OSPF did take a Distribute list IN via the tunnel. I denied the local
> link's network ... and all was well in la-la land (where I live).
>
> R1(config-router)#distribute-list 12 in tunnel 1
>
> Would have been easier and quicker for me to simply remove the physical
> link's network from OSPF, but I was / am learning ...
>
> Also, ... I actually prefer a distribute list IN, since if I am able to
> keep
> the physical link's network in OSPF on my hub router, other peers will
> still
> learn about it. I am only filtering via these two routers, and all other
> routers still learn about the local link's network.
>
> Question for the group:
>
> For recursive learning, any additional thoughts on ways for me to learn
> this
> / explore this / solve this?
>
> I suppose in all of life, the kiss method is the best ... Just figured I
> would ping yall to see what insights I might learn.
>
> Many TIA,
>
> Andrew Lee Lissitz
>
> --
> Andrew Lee Lissitz
> all.from.nj@gmail.com
>
>
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