eBGP to EIGRP can not redistribute!! Is it just specification right?

[mhiyoshi]

Dear all,

I have just thought about the attached scenario, but I am wondering whether it is specification or not.
In my opinion if eBGP peer IP address changes but redistribution from eBGP to EIGRP can also be possible as a triggered update right?

[Summary log]
C891FJ#sh ip bgp summary | in 10.0.10.1
10.0.10.1 4 1 23 22 3 0 0 00:17:00 2

Cat3560G#sh ip route eigrp | in 1.1.1.1
D EX 1.1.1.1 [170/30720] via 10.0.20.254, 00:16:28, GigabitEthernet0/1

■Execute the following configuration on C891FJ.

no router bgp 2
router bgp 2
neighbor 10.0.10.2 remote-as 1

■After that it can be seen as follows. C891FJ can do eBGP peer and receive 1.1.1.1/32 route however C891FJ does't have its EIGRP topology table.

C891FJ#sh ip bgp summary | in 10.0.10.2
10.0.10.2 4 1 5 4 3 0 0 00:00:17 2

C891FJ#sh ip route bgp | in 1.1.1.1
B 1.1.1.1 [20/0] via 10.0.10.2, 00:00:37

C891FJ#sh ip eigrp topology
EIGRP-IPv4 Topology Table for AS(1)/ID(10.0.20.254)
Codes: P - Passive, A - Active, U - Update, Q - Query, R - Reply,
r - reply Status, s - sia Status
P 10.0.20.0/24, 1 successors, FD is 28160
via Connected, FastEthernet0

Cat3560G#sh ip route eigrp | in 1.1.1.1

■Next configure on C891FJ as follows.

Actually it can not be resolved by interface shut/no shut or clear ip eigrp neighbors.

 but reload or only the following configuration can be posssible to resolve.

router eigrp 1
redistribute bgp 2 metric 300000 10 1 1 1 *This configuration already exists on C891FJ but it just overrides with same one.

■After that C891FJ has its EIGRP topology table below. and Cat3560G receives 1.1.1.1/32 route.

C891FJ#sh ip eigrp topology
EIGRP-IPv4 Topology Table for AS(1)/ID(10.0.20.254)
Codes: P - Passive, A - Active, U - Update, Q - Query, R - Reply,
r - reply Status, s - sia Status
P 10.0.20.0/24, 1 successors, FD is 28160
via Connected, FastEthernet0

P 1.1.1.1/32, 1 successors, FD is 11008, tag is 1
via Redistributed (11008/0)

Cat3560G#sh ip route eigrp | in 1.1.1.1
D EX 1.1.1.1 [170/30720] via 10.0.20.254, 00:00:02, GigabitEthernet0/1

I appreciate if you can let me know any related information.

Best Regards,

Masanobu Hiyoshi

[Georg Pauwen]

Hello,

I think what you see is normal behavior. The only way to redistribute and update the DNDB is by having both processes active and then redistribute. If you delete the BGP process, the redistribution doesn't automatically reoccur when you add the BGP process again. You need to manually trigger it.

Have a look at the below 'debug eigrp transmit' from C891FJ:

C891FJ#debug eigrp transmit
(ACK, PACKETIZE, STARTUP, PEERDOWN, LINK, BUILD, STRANGE, SIA, DETAIL)
EIGRP Transmit debugging is on
C891FJ#conf t
Enter configuration commands, one per line. End with CNTL/Z.
C891FJ(config)#router eigrp 1
C891FJ(config-router)#redistribute bgp 2 metric 300000 10 1 1 1
C891FJ(config-router)#
*Nov 21 09:27:56.779: DNDB UPDATE 1.1.1.1/32, serno 0 to 5, refcount 1

[paul driver]

Hello
Hum... So your perfroming mutual redistribution and then you remove the bgp routing process and re-add it?

If i am not mistaken the redistrubtion statment of bgp into eigrp will be removed from the eigrp stanza when you remove the bgp routing process , So this will have to  re-added

No need to reload or clear anything surely?

res
Paul

[mhiyoshi]

Hello Georg and Paul,

Thank you for your precious comments! I have been verifying what the EIGRP DNDB is going on.
So I would like to be more talkative about the tips below.

> No need to reload or clear anything surely?

So you mean that if BGP peer configures again then automatically redistribute to EIGRP ?

Or after delete BGP configuration like "no router bgp X" then EIGRP redistribute configuration like the following
is necessary before re-added the BGP configuration you mentioned right?

C891FJ(config)#router eigrp 1
C891FJ(config-router)# redistribute bgp 2 metric 300000 10 1 1 1

Mind if you could let me know any related documentation URL like CCO, RFC etc?

> Please don't forget to rate any posts that have been helpful. Thanks.

This is very helpful so I have just clicked on the 5 stars. Cheers ^..

Best Regards

Masanobu Hiyoshi

[paul driver]

Hello

From what you have described, Once you removed and re-added the bgp router process, Eigrp was still adverted into bgp due to the fact the eigrp process wasn't changed.

However the bgp redistribution routes were removed from eigrp because the bgp redistribution commend  under eigrp was removed when the bgp process was.

So what you are seeing if basically no redistribution occurring because the redistribution statement was removed, Which it is normal behavior for the rtr , To remove any redistribution when the related primary router process is also removed., So it doesn't need to be triggered or reloaded in anyway but just redistributed again.

res
Paul

[mhiyoshi]

Hello Paul

Thank you very much! Well I have verified another testing below.

TEST1 - BGP to OSPF : Redistribution command under OSPF was deleted automatically when it configured "no router bgp x".
*Normally I do not notice this behavior but I know it must configure redistribution command again. That is why no issue happen.

TEST2 - BGP to EIGRP : Redistribution command under EIGRP was not deleted automatically when it configured "no router bgp x".

So my conclusion is that this is normal behavior to treat redistribution between routing protocols.

However when I have compared with the above testing, it was quite different.

Currently only EIGRP redistribution configs not automatically removed when it executes "no router bgp".

So yes, now I have been understanding what it is. but if you do not mind please let me know any relative CCO documentation for example this normal behavior info is written by configuration guides, command reference etc.

Best Regards,

Masanobu Hiyoshi

[paul driver]

Hello

---

@mhiyoshi wrote:

TEST2 - BGP to EIGRP : Redistribution command under EIGRP was not deleted automatically when it configured "no router bgp x".

Well that is quite strange I would have envisage it to be removed -  How have you tested this?

---

res
Paul

[mhiyoshi]

Hi Paul,

> Well that is quite strange I would have envisage it to be removed -  How have you tested this?

 I think so but now I have already verified that C891FJ actually can do this behavior. I am not sure other routers can also do like this.

Best Regards,

Masanobu Hiyoshi

[paul driver]

Hello

---

@mhiyoshi wrote:

Hi Paul,

> Well that is quite strange I would have envisage it to be removed -  How have you tested this?

 I think so but now I have already verified that C891FJ actually can do this behavior. I am not sure other routers can also do like this.

Best Regards,

Masanobu Hiyoshi

---

Its not the rtr it will be to IOS that is dong it,

However FYI- I have now labbed this up myself for verification with mixed results ( c2800nm-adventerprisek9_ivs-mz.151-3.T4)  and my tests do show the redistribute statement not being removed  running eigrp

However running c3725-adventerprisek9-mz.124-15.T14  it did remove the redistrubte statment

Interesting.......

res
Paul

[paul driver]

Hello

I have now tested this on numerous platforms and I think its got to be a bug -We the most recent IOS I could lay my hands on for the following routers -1921,2650xm,2811,3725

The 1900,3725  do remove the redistribution of bgp from eigrp when its related bgp process is removed but the 2600,2800 ios don't.

With the 1900,3725 as I  would have expected I had to re-insert the redistribution statement when I re-added the bgp process.

However for the latter, Although the redistribution bgp statement Isn't removed from the eigp process , Its Defiantly does NOT relate to any re-added bgp process, So although it is seen in the eigrp router process the redistribution bgp statement needs to be re-added as if it was removed, then once again redistribution of bgp starts to work.

Now that is some caveat !!!!

Would be very interested if anyone else can verify what I have tested on other IOS preferably also with named eigrp if applicable.

res
Paul

[mhiyoshi]

Hello Paul

That would be very helpful, I think delete redistribution command depends on the product and software.

However all we have to do is just to know this documentation. 

Any related information would be very helpful! Thank you.

Best Regards,

Masanobu Hiyoshi