Cisco Support Community
cancel
Showing results for 
Search instead for 
Did you mean: 
Announcements

Welcome to Cisco Support Community. We would love to have your feedback.

For an introduction to the new site, click here. If you'd prefer to explore, try our test area to get started. And see here for current known issues.

New Member

EIGRP Summary Route.

I am looking at two 1600 series routers connected via Ethernet. On one of the 1600 I have interface loopback 1 with an ip address 200.1.1.1/24 and want to summarise (via EIGRP) this to the other 1600 router as 200.0.0.0/8.

I have entered the following under the Ethernet interface:

ip summary-address eigrp 1 200.0.0.0 255.0.0.0 5

where 1=AS and 5 is the admin distance for a summary route (default). The problem is, the route is showing in my routing table but with an admin dis of 90 (internal EIGRP) instead of 5. Am I right is thinking this should be 5? I have looked at the bug toolkit and cannot find it as a bug - what is wrong?

Thanks,

Dazzler.

1 ACCEPTED SOLUTION

Accepted Solutions
Silver

Re: EIGRP Summary Route.

Dazzler,

Here's the deal with the 5. Yes, you are correct that this is this distance of the summary.. but only locally. When an EIGRP summary goes out to other routers on the interface you've placed it it applies the smallest metric of all specifics (90) and sends it out. To verify this please do the following on the router that you've made your summary.

R1#sh ip route 200.0.0.0

Routing entry for 200.0.0.0/8, supernet

Known via "eigrp 1", distance 5, metric 128256, type internal <--- distance is 5

Redistributing via eigrp 1

Routing Descriptor Blocks:

* directly connected, via Null0

Route metric is 128256, traffic share count is 1

Total delay is 5000 microseconds, minimum bandwidth is 10000000 Kbit

Reliability 255/255, minimum MTU 1514 bytes

Loading 1/255, Hops 0

Here the summary is learned.

R2>sh ip route 200.0.0.0

Routing entry for 200.0.0.0/8, supernet

Known via "eigrp 1", distance 90, metric 409600, type internal <--- distance 90

Redistributing via eigrp 1

Last update from 2.2.2.1 on Ethernet0/0, 00:27:34 ago

Routing Descriptor Blocks:

* 2.2.2.1, from 2.2.2.1, 00:27:34 ago, via Ethernet0/0

Route metric is 409600, traffic share count is 1

Total delay is 6000 microseconds, minimum bandwidth is 10000 Kbit

Reliability 255/255, minimum MTU 1500 bytes

Loading 1/255, Hops 1

So you are seeing the proper function (if your local route is distance of 5) which I am assuming it is.

Hope this helps explain,

Don

3 REPLIES
Silver

Re: EIGRP Summary Route.

Dazzler,

Here's the deal with the 5. Yes, you are correct that this is this distance of the summary.. but only locally. When an EIGRP summary goes out to other routers on the interface you've placed it it applies the smallest metric of all specifics (90) and sends it out. To verify this please do the following on the router that you've made your summary.

R1#sh ip route 200.0.0.0

Routing entry for 200.0.0.0/8, supernet

Known via "eigrp 1", distance 5, metric 128256, type internal <--- distance is 5

Redistributing via eigrp 1

Routing Descriptor Blocks:

* directly connected, via Null0

Route metric is 128256, traffic share count is 1

Total delay is 5000 microseconds, minimum bandwidth is 10000000 Kbit

Reliability 255/255, minimum MTU 1514 bytes

Loading 1/255, Hops 0

Here the summary is learned.

R2>sh ip route 200.0.0.0

Routing entry for 200.0.0.0/8, supernet

Known via "eigrp 1", distance 90, metric 409600, type internal <--- distance 90

Redistributing via eigrp 1

Last update from 2.2.2.1 on Ethernet0/0, 00:27:34 ago

Routing Descriptor Blocks:

* 2.2.2.1, from 2.2.2.1, 00:27:34 ago, via Ethernet0/0

Route metric is 409600, traffic share count is 1

Total delay is 6000 microseconds, minimum bandwidth is 10000 Kbit

Reliability 255/255, minimum MTU 1500 bytes

Loading 1/255, Hops 1

So you are seeing the proper function (if your local route is distance of 5) which I am assuming it is.

Hope this helps explain,

Don

New Member

Re: EIGRP Summary Route.

Thanks Don that makes sense.

Let me just put it in my own words and you can verify whether I've grasped it correctly. When you specify an 'ip summary-address', the router has to place the 'route' into the routing table - after all, the router will only communicate networks that are in it's table (via any routing protocol - not just EIGRP). The reason, 200.0.0.0/8 points to the Null interface is because the router (that generates the summary) should know about all the networks it is summarising. The reason the default admin is low is because someone has manually entered the command and it is assumed they have carefully considered theimpact of entering such a command.

Thanks again.

Silver

Re: EIGRP Summary Route.

Sounds good to me. ;)

Don

239
Views
0
Helpful
3
Replies