Solved: EIGRP missing Topology table entry

Kishore Chennupati · ‎11-13-2011

Hello fellow engineers,

Got a setup

Default route Default Route

R1 R2 .21

| | .22

R3 R4 .25

| | .26

sw1---------------------------sw2

.33 .34

Now, the above network is all layer 3 and running Eigrp. Now , on R1 and R2 default static is redistrributed into eigrp.

when I check the topology table on sw2 I should be seeing 2 entries for default route right? but I dont Howver I can see it on R4

sw2:

#sh ip eigrp topology 0.0.0.0

EIGRP-IPv4:(180) (AS 180): Topology Default-IP-Routing-Table(0) entry for 0.0.0.0/0

State is Passive, Query origin flag is 1, 1 Successor(s), FD is 3840

Descriptor Blocks:

10.183.2.33 (Port-channel1), from 10.183.2.33, Send flag is 0x0

Composite metric is (3840/3584), Route is External

Vector metric:

Minimum bandwidth is 1000000 Kbit

Total delay is 50 microseconds

Reliability is 255/255

Load is 1/255

Minimum MTU is 1500

Hop count is 4

External data:

Originating router is 10.183.20.253

AS number of route is 0

External protocol is Static, external metric is 0

Administrator tag is 0 (0x00000000)

Exterior flag is se

R4

#sh ip eigrp topology 0.0.0.0/0

IP-EIGRP (AS 180): Topology entry for 0.0.0.0/0

State is Passive, Query origin flag is 1, 1 Successor(s), FD is 4096

Routing Descriptor Blocks:

10.183.2.26 (GigabitEthernet0/1), from 10.183.2.26, Send flag is 0x0

Composite metric is (4096/3840), Route is External

Vector metric:

Minimum bandwidth is 1000000 Kbit

Total delay is 60 microseconds

Reliability is 255/255

Load is 1/255

Minimum MTU is 1500

Hop count is 5

External data:

Originating router is 10.183.20.253

AS number of route is 0

External protocol is Static, external metric is 0

Administrator tag is 0 (0x00000000)

Exterior flag is set

10.183.2.21 (GigabitEthernet0/0), from 10.183.2.21, Send flag is 0x0

Composite metric is (28672/3072), Route is External

Vector metric:

Minimum bandwidth is 100000 Kbit

Total delay is 120 microseconds

Reliability is 255/255

Load is 1/255

Minimum MTU is 1500

Hop count is 2

External data:

Originating router is 10.183.252.2

AS number of route is 0

External protocol is Static, external metric is 0

Administrator tag is 0 (0x00000000)

Exterior flag is set

so why is the sw2 not seeing the default route from .25 in its topology table. If you need me to provide you an info, please let me know and I provide it here

Regards

Kishore

dslice · ‎11-14-2011

Isn't .25 R4? If so, then the answer is split horizon. R4 is using sw2 as his successor so he won't send an update out to sw2. Split horizon states that you don't advertise out the interface you're using to reach the destination.

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smitesh kharecha · ‎11-13-2011

Hi Kishor,

Have you configure variance under EIGRP ?

If not, can you please check by configuring variance 2 and post your feedback.

Regards,

Smitesh

smitesh kharecha · ‎11-13-2011

Hi,

Came back to check this and found that @ SW2 FD is not meeting.

Regards,

Smitesh

Kishore Chennupati · ‎11-14-2011

sorry smitesh. what do u mean by not meeting?? can u please explain further

Thanks

Kishore

smitesh kharecha · ‎11-14-2011

Hi Kishore,

Can you please calculate the composite metric expected till SW2 from both sides of SW2.

I agree that i incorrectly made a statement that it is not meeting, however I made a that statement by comparing the metric on R4 (I know that not correct, however sometimes it gives you the rough idea. hence I came to conclusion that it is adding over 800 to composite metric)

I hope you get my point, where am I pointing.

Regards,

Smitesh

Kishore Chennupati · ‎11-14-2011

hi smitesh.

sw2 learns the default route via sw1 and R4 and by the calculation it finds that the FD via sw1 is lower than the FD via R4 so it installs that as succesor and in the routing table. Then it see whether the route via R4 can become a FS so its checks that RD from R4 which is 3072 and this is less than 3840 which is the FD so the condition is met RD

smitesh kharecha · ‎11-14-2011

Hi Kishore,

3072 is till the R4. So you have to add the outgoing interface metrics from R4 towards SW2 too, and then check whether FD is meeting ??

Regards,

Smitesh

Kishore Chennupati · ‎11-14-2011

hi smitesh isnt RD what the neigbor tells about how to get to the remote network?

When you add the metric from sw2 as well then that becomes the FD which as I said seems to be higher than 3840 learned from sw1 and thats why it doesnt choose the route learned via R4 as successor. would I be right?

dslice · ‎11-14-2011

Isn't .25 R4? If so, then the answer is split horizon. R4 is using sw2 as his successor so he won't send an update out to sw2. Split horizon states that you don't advertise out the interface you're using to reach the destination.

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Kishore Chennupati · ‎11-14-2011

Hi Don,

If I look at sw2 eigrp events I see its receiving it from .25

sw2#sh ip eigrp events | i 0.0.0.0

105 12:14:03.596 Metric set: 0.0.0.0/0 3840

106 12:14:03.596 Route install: 0.0.0.0/0 10.183.2.33

107 12:14:03.596 RDB delete: 0.0.0.0/0 10.183.2.25

110 12:14:03.596 Find FS: 0.0.0.0/0 3840

112 12:14:03.596 Rcv update dest/nh: 0.0.0.0/0 10.183.2.25

286 12:14:03.554 Metric set: 0.0.0.0/0 3840

288 12:14:03.554 Update sent, RD: 0.0.0.0/0 28928

290 12:14:03.554 Update sent, RD: 0.0.0.0/0 28928

291 12:14:03.554 Route install: 0.0.0.0/0 10.183.2.33

292 12:14:03.545 Route install: 0.0.0.0/0 10.183.2.25

295 12:14:03.545 Find FS: 0.0.0.0/0 28928

297 12:14:03.545 Rcv update dest/nh: 0.0.0.0/0 10.183.2.33

337 12:13:54.360 Poison squashed: 0.0.0.0/0 reverse

353 12:13:54.326 RDB delete: 0.0.0.0/0 10.183.2.33

370 12:13:54.133 Route OBE net/refcount: 0.0.0.0/0 2

Regards

Kishore

Shahaludeen N · ‎11-14-2011

For SW2 the FD for 0.0.0.0 is 3840. Now, in order for anyone to be a feasible successor, their reported distance should be less than the FD(3840) but the distance that would be reported by R4 is 28672 and that is not less than the FD(3840), so it will fail the feasibility condition.

dslice · ‎11-15-2011

The above event log shows what happened when the route was removed via .33. Notice the RDB delete? At that point, the prefix would be advertised from .25. Since your topo table in the first output shows how it looks when the .33 route is intact, the route from .25 would not be advertised at that point. Is this continually changing?

Kishore Chennupati · ‎11-15-2011

Hi Don,

Thanks for your reply. If you look at the event table it also has another entry

353 12:13:54.326 RDB delete: 0.0.0.0/0 10.183.2.33 This is where its learning the best path from . So it doesnt make sense that it would delete it right?

Also, to add to some more fun , lets assume that its split horizon and R4 is not advertising to sw2.

But when I look at the topo table on R1. I see its learning the default route that R2 sent to R4.

R1#sh ip eigrp topology 0.0.0.0/0

IP-EIGRP (AS 180): Topology entry for 0.0.0.0/0

State is Passive, Query origin flag is 1, 1 Successor(s), FD is 2816

Routing Descriptor Blocks:

10.183.20.1, from Rstatic, Send flag is 0x0

Composite metric is (2816/0), Route is External

Vector metric:

Minimum bandwidth is 1000000 Kbit

Total delay is 10 microseconds

Reliability is 255/255

Load is 1/255

Minimum MTU is 1500

Hop count is 0

External data:

Originating router is 10.183.20.253 (this system)

AS number of route is 0

External protocol is Static, external metric is 0

Administrator tag is 0 (0x00000000)

Exterior flag is set

10.183.2.2 (GigabitEthernet1/0/2), from 10.183.2.2, Send flag is 0x0 <<<< This is R3

Composite metric is (29952/29696), Route is External

Vector metric:

Minimum bandwidth is 100000 Kbit

Total delay is 170 microseconds

Reliability is 255/255

Load is 1/255

Minimum MTU is 1500

Hop count is 7

External data:

Originating router is 10.183.252.2 <<<< This is R2

AS number of route is 0

External protocol is Static, external metric is 0

Administrator tag is 0 (0x00000000)

Appreciate your thoughts with this

Regards

Kishore

dslice · ‎11-15-2011

the event log isn't complete so you're missing the event that caused the route to be deleted. It happened before line 370. It also appears that the statics are changing. They aren't floating statics, are they? It might be helpful to supply configs, topo tables, and event logs from all routers.

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Kishore Chennupati · ‎11-15-2011

Hi Don,

Nah no flating statics. Just normal statics being redistributed. I can supply the configs Is there anything particular that you seek that could help?

..... It also appears that the statics are changing.

I didnt get you here. can I please request you to explain a bit more?

Thanks again for your inputs

Kishore