why is ospf forward address not 0.0.0.0 in this case?

[jleszewski]

Hi,

I have a two N7k switches configured as ASBRs.

Problem with one of them is that it sets forward address on default route it distributes into the nssa area to the ip address of it's connection in this area.

This causes the default gateway loop further in this nssa area, because this path is selected by second asbr connecting this area to the backbone.

Topology look more or less like this:

core-router

|              \

|    area 0  \

|                \

asbr1------asbr2

|               |

|     nssa   |

r1------------r2

Now asbr1 installs default route via r1, because it sees the forward address pointing to the connection r2-asbr2.

And of course r1 installs default route via asbr1, because asbr1 has 'default information originate" configured for this area.

ps

I have another pair of N7k configured the same way (at least it looks the same) in another site, and there is no such problem there.

Both asbrs redistribute default route with forward address set to 0.0.0.0

Can anyone point me to a solution of this problem?

regards

Kuba

[Rolf Fischer]

Seems like a bug... ?

I suppose so too. In any case a very strange malfunction which to my best knowledge cannot be caused by misconfiguration.

If the problem remains after a clearing (or reboot), I'd recommend to contact TAC.

Please keep us up-to-date!

[jleszewski]

Clearing ip ospf neighbour didn't help

But it helped when i removed interface to r2 on asbr2 from ospf, and put it again into ospf.

Everything looks good now.

show ip ospf database nssa-external 0.0.0.0  detail

        OSPF Router with ID (10.2.1.1) (Process ID 10 VRF default)

                Type-7 AS External Link States (Area 0.0.0.60)

   LS age: 914

   Options: 0 (No TOS-capability, No Type 7/5 translation, No DC)

   LS Type: Type-7 AS-External

   Link State ID: 0.0.0.0 (Network address)

   Advertising Router: 10.2.1.1

   LS Seq Number: 0x8000242f

   Checksum: 0xaec2

   Length: 36

   Network Mask: /0

         Metric Type: 2 (Larger than any link state path)

         TOS: 0

         Metric: 1

         Forward Address: 0.0.0.0

         External Route Tag: 0

   LS age: 653

   Options: 0 (No TOS-capability, No Type 7/5 translation, No DC)

   LS Type: Type-7 AS-External

   Link State ID: 0.0.0.0 (Network address)

   Advertising Router: 10.2.1.5

   LS Seq Number: 0x80002434

   Checksum: 0x8cdb

   Length: 36

   Network Mask: /0

         Metric Type: 2 (Larger than any link state path)

         TOS: 0

         Metric: 1

         Forward Address: 0.0.0.0

         External Route Tag: 0

Thanks for Your help :-)

[Rolf Fischer]

A very good approach since this was the link advertised as the FA.

Thanks for the feedback!