distribution list

[miracle_david@yahoo.com]

Hi,
In "https://www.cisco.com/c/en/us/support/docs/ip/enhanced-interior-gateway-routing-protocol-eigrp/16406-eigrp-toc.html?dtid=osscdc000283#anc0" part "How Distribution Lists Affect the Query Range" I wish to know what's the config for "distribution list" that prevent router "one" from receiving reply from router "three" about Network a.

Thanks in advance

[Georg Pauwen]

Hello,

I am not clear on what you are asking. The update for Network A would get to Router One through the neighboring, directly connected router, and not go through Router three. You can specify a distribute list that would prevent updates from Router Three through a specific interface. Let''s say network A is 3.3.3.3/32. If you don't want to get the update from Router 3, the distribute list would look like this:

Router One

router eigrp 1

distribute-list 1 in GigabitEthernet0/0 --> interface connected to Router Two

!

access-list 1 deny 3.3.3.3 0.0.0.0

access-list 1 permit any

You would still get the update, but never through Router Three.

[miracle_david@yahoo.com]

Hi sir, thank you for your cooperation in replying my query. As the figure illustrates, distribution list is configured on R3.

I'd be glad if I can know where u r from & whether u live in US or not.

All the best

[Cristian Matei · Accepted solution]

Hi,

    You configure R3 to send updates out on its Serial ports only about Network B, and not about Network A.

Network A = 10.10.10.0/24

Network B = 20.20.20.0/24

R3 First Solution:

access-list 10 permit 20.20.20.0

router EIGRP 100

 distribute-list 10 out Serial0/0

 distribute-list 10 out Serial1/0

R3 Second Solution:

ip prefix-list EIGRP permit 20.20.20.0/24

router EIGRP 100

 distribute-list prefix EIGRP out Serial0/0

 distribute-list prefix EIGRP out Serial1/0

R3 Third Solution:

ip prefix-list EIGRP permit 20.20.20.0/24

access-list 10 permit 20.20.20.0

route-map EIGRP permit 10

 match ip address prefix-list EIGRP  OR match ip address 10

router EIGRP 100

 distribute-list route-map EIGRP out Serial0/0

 distribute-list route-map EIGRP out Serial1/0

Regards,

Cristian Matei.

[miracle_david@yahoo.com]

Thanks sir for your spectacular reply. There r still some vague points in this article.

1. The figure doesn't show Net B, is it located behind R3?

2. R3 is connected to others, how come it says "Routers One and Two do not know that Network A is reachable through Router Three". Also, Net A isn't reachable for R1 & R2, so how can it can be reached by R3?

3. The article says "Router Three uses Router One as its preferred path to Network A, and does not use Router Two as a feasible successor". Why doesn't it use R2 as feasible successor?

I thinks this article is wrong but surely expecting to hearing your idea.

P.S I wish one day I could excel you in CISCO

[Cristian Matei · Accepted solution]

Hi,

  1. Yes, network B is behind R3 or connected to R3 only.

  2. Network A is connected to R1 and R2, so R1 and R2 send updates about Network A to R3. Since R3's best path is via R1 or R2, it doesn't send an update back out that link for Network A, because of split-horizon rule.

 3. The scenario is hypothetic, but can be achieved via delay/BW manipulation; any secondary EIGRP paths for a prefix (with a metric higher than the one of the successor), are only taken into consideration if they meet the feasibility(loop-prevention) condition, which is the AD of Feasible Successor < FD of Successor.

The article is correct.

Regards,

Cristian Matei.