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New Member

Distribute list question

Hi,

Is multiple distribute list acceptable?

router eigrp 10

distribute-list 20 out interface tu0

distribute-list 30 out

Thanks.

  • WAN Routing and Switching
2 ACCEPTED SOLUTIONS

Accepted Solutions
Hall of Fame Super Blue

Re: Distribute list question

marcusbrutus wrote:

Or should I do the below instead?

int tu0

ip summary-address eigrp 1 10.55.0.0 255.255.0.0


*and just remove the distribute list from the eigrp process?


Note: 

Basically, i am looking to just advertise 10.55.0.0/24 out via the tu0 and advertise everything else out the remainint interfaces.

Marcus

Personally if you can use the EIGRP summary address then i would do that. Couple of things to note -

Is 10.55.0.0/24 a directly connected network on the router ? The reason i ask is that when you create a summary route EIGRP places the route into the local routers table with an AD of 5 and a next-hop of null0. If this router is actually learning the 10.55.0.0/24 network from another router then it that route it learns will have an AD of 90 so you have blackholed that network because the null0 route is preferred because of it's AD.

Having said that your summary route subnet-mask in the above example is 255.255.0.0 not 255.255.255.0 so the above may not apply. Basically what the above will do is for any routes that are more specific than 10.55.0.0/16 eg. 10.55.0.0/24, 10.55.1.0/24 etc.. those routes will work fine on the local router and traffic will be forwarded correctly.

For any 10.55.x.0 networks that do not have routes in the local routing table, these will be blackholed ie. sent to null0 which may well be what you want anyway.

Jon

Bronze

Re: Distribute list question

yes multiple distribute list can be used. Below link gives more detail.

http://www.cisco.com/en/US/tech/tk365/technologies_tech_note09186a0080208748.shtml

Thanks,

Madhu

4 REPLIES
New Member

Re: Distribute list question

Or should I do the below instead?

int tu0

ip summary-address eigrp 1 10.55.0.0 255.255.0.0


*and just remove the distribute list from the eigrp process?


Note: 

Basically, i am looking to just advertise 10.55.0.0/24 out via the tu0 and advertise everything else out the remainint interfaces.

Hall of Fame Super Blue

Re: Distribute list question

marcusbrutus wrote:

Or should I do the below instead?

int tu0

ip summary-address eigrp 1 10.55.0.0 255.255.0.0


*and just remove the distribute list from the eigrp process?


Note: 

Basically, i am looking to just advertise 10.55.0.0/24 out via the tu0 and advertise everything else out the remainint interfaces.

Marcus

Personally if you can use the EIGRP summary address then i would do that. Couple of things to note -

Is 10.55.0.0/24 a directly connected network on the router ? The reason i ask is that when you create a summary route EIGRP places the route into the local routers table with an AD of 5 and a next-hop of null0. If this router is actually learning the 10.55.0.0/24 network from another router then it that route it learns will have an AD of 90 so you have blackholed that network because the null0 route is preferred because of it's AD.

Having said that your summary route subnet-mask in the above example is 255.255.0.0 not 255.255.255.0 so the above may not apply. Basically what the above will do is for any routes that are more specific than 10.55.0.0/16 eg. 10.55.0.0/24, 10.55.1.0/24 etc.. those routes will work fine on the local router and traffic will be forwarded correctly.

For any 10.55.x.0 networks that do not have routes in the local routing table, these will be blackholed ie. sent to null0 which may well be what you want anyway.

Jon

Hall of Fame Super Blue

Re: Distribute list question

Marcus

Sincere apologies, that has to be one of the most confusing posts i have ever written, even i am having trouble understanding it.

And on second thoughts a summary address is not the way to go because you are not actually summarising anything. Use distribute-lists as you suggested in your first post, it should work fine.

If you want to advertise the remaining routes out everywhere else though why do you need a 2nd distribute-list ? -do you still need to filter that set of routes ?

Jon

Bronze

Re: Distribute list question

yes multiple distribute list can be used. Below link gives more detail.

http://www.cisco.com/en/US/tech/tk365/technologies_tech_note09186a0080208748.shtml

Thanks,

Madhu

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