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eigrp summary routes query

marcusbrutus
Level 1
Level 1

Hi Experts,

 

I am summarizing eigrp on a lan interface (gi0/0) attached to a router.  Summary is 10.0.0.0/8.  Gi0/0 IP is 10.1.1.1.

 

Problem is that when the router uplink goes down and it looses all of the other 10.x routes, it is still advertising the summary because the directly connected interface is withing the summary range (10.1.1.1).  This is causing traffic to blackhole to this router.

 

I tried to explore all possible workarounds for this but am unsuccessful.

 

Hope you guys can help me.

 

 

1 Accepted Solution

Accepted Solutions

I can't really think of another way to do this other than EEM I'm afraid.

However I had a bit of time today and did some quick testing with EEM as I haven't used it before and it's actually not that complicated if you just use an applet.

You should be able to type the following into your router -

event manager applet REMOVESUMMARY                                                
 event syslog pattern ".*%LINEPROTO-5-UPDOWN: Line protocol on Interface Etherne
t0/3, changed state to down.*"                                                 
 action 2.0 cli command "enable"                                               
 action 2.1 cli command "conf t"                                               
 action 2.2 cli command "int eth0/2"                                           
 action 2.3 cli command "no ip summary-address eigrp 10 192.168.0.0 255.255.0.0"

event manager applet ADDSUMMARY                                                  
 event syslog pattern ".*%LINEPROTO-5-UPDOWN: Line protocol on Interface Etherne
t0/3, changed state to up.*"                                                   
 action 2.0 cli command "enable"                                               
 action 2.1 cli command "conf t"                                               
 action 2.2 cli command "int eth0/2"                                           
 action 2.3 cli command "ip summary-address eigrp 10 192.168.0.0 255.255.0.0"  

and that's all you need.

A few points of explanation -

1) the syslog pattern needs to match what the router reports when the interface goes down. Obviously your interface will be different and perhaps the message. If you need to modify it then make sure you include the .* (dot/star) at the beginning and the end.

It should be fairly close though already. Make sure you copy it exactly ie. where there are spaces in the message put them in the string.

2) from the above the interface monitored is eth0/3 and the interface you are advertising the summary address on is eth0/2

I tested it a number of times ie. shutting down and bringing up  the interface and it worked fine.

It doesn't do any error checking but it is fairly basic in terms of what it is doing ie. simply adding and removing a summary route.

What do you think ?

Edit - I tested on IOS 15.4. I assume the commands would be the same on your router.

Jon

 

View solution in original post

6 Replies 6

Jon Marshall
Hall of Fame
Hall of Fame

It's not clear where the traffic should go if this router fails ?

A general answer to your question my be look at EEM where you can have script running on the router that monitors the uplink and if it goes down removes the summary address.

You should be able to do a search to find an EEM script that does something similar and modify it for your needs.

But perhaps a few more details might help.

Jon

Hi Jon,

 

I have a lot of 10.x routes coming from the WAN into my edge CE router.  I wish to limit the number of prefixes advertised into the LAN switches by summarizing.  I have another standby CE also doing the same thing.  I wish the primary CE to stop advertising the 10.0.0.0 summary when all the 10.x routes get lost.  But this is not happening given the CE lan interface 10.1.1.1.

I will consider the EEM solution but would appreciate a simpler one.

 

Thanks!!

Just a quick follow up before I log off for the evening.

If you have any doubts about using the configuration I posted then by all means post into the EEM forum, or move this post to there to get it checked out ie. is it the best approach, will it work with your IOS etc.

I certainly won't be offended as this is your production network and although it worked in my lab it is the first time I have used it.

Jon

I can't really think of another way to do this other than EEM I'm afraid.

However I had a bit of time today and did some quick testing with EEM as I haven't used it before and it's actually not that complicated if you just use an applet.

You should be able to type the following into your router -

event manager applet REMOVESUMMARY                                                
 event syslog pattern ".*%LINEPROTO-5-UPDOWN: Line protocol on Interface Etherne
t0/3, changed state to down.*"                                                 
 action 2.0 cli command "enable"                                               
 action 2.1 cli command "conf t"                                               
 action 2.2 cli command "int eth0/2"                                           
 action 2.3 cli command "no ip summary-address eigrp 10 192.168.0.0 255.255.0.0"

event manager applet ADDSUMMARY                                                  
 event syslog pattern ".*%LINEPROTO-5-UPDOWN: Line protocol on Interface Etherne
t0/3, changed state to up.*"                                                   
 action 2.0 cli command "enable"                                               
 action 2.1 cli command "conf t"                                               
 action 2.2 cli command "int eth0/2"                                           
 action 2.3 cli command "ip summary-address eigrp 10 192.168.0.0 255.255.0.0"  

and that's all you need.

A few points of explanation -

1) the syslog pattern needs to match what the router reports when the interface goes down. Obviously your interface will be different and perhaps the message. If you need to modify it then make sure you include the .* (dot/star) at the beginning and the end.

It should be fairly close though already. Make sure you copy it exactly ie. where there are spaces in the message put them in the string.

2) from the above the interface monitored is eth0/3 and the interface you are advertising the summary address on is eth0/2

I tested it a number of times ie. shutting down and bringing up  the interface and it worked fine.

It doesn't do any error checking but it is fairly basic in terms of what it is doing ie. simply adding and removing a summary route.

What do you think ?

Edit - I tested on IOS 15.4. I assume the commands would be the same on your router.

Jon

 

Sorry for the late reply Jon;  been a hectic-crazy couple of weeks.

I appreciate your time and attention to this.

 

Dan Mullendore
Level 1
Level 1

I have the same problem, but it is beause the loopback address on the router is in the summary range and with dual connections back to the core, half of the traffic would still try to head toward the summary routes.

Looks like an eligant solution, but I am going to have to test this in production!  First time I have used the event manager. 

Thanks.

Dan

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