EIGRP and default route

Unanswered Question
Jul 16th, 2008

I have a 4506 acting as a HUB and about 5 3560's configured as STUB. All of the 3560's connect to a layer 2 switch which is plugged into one port on the 4506. If i configure ip summary-address eigrp 1 on that interface, will it propagate that default route dynamically to all of the 3560s? I have the 3560's configured as....


router eigrp 100



eigrp stub connected summary


I also have a default route manually configured on all of the 3560s, The routing tables of the 3560's are pretty big. It would be nice to just push a default route dynamically to them all to shrink the table. Also, the IP DEFAULT NETWORK command isn't configured on my switches. Do i need this on the 3560's? Any suggestions?

I have this problem too.
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lee.reade Wed, 07/16/2008 - 05:08


You must configure the summary address on the layer 3 interface that peers with a 3560 via eigrp.

Do the 3560's peer with the 4506 via eigrp across the same vlan? If so then config that vlan interface on the 4506 with the summary address, and it will propagate down.



cowetacoit Wed, 07/16/2008 - 05:11

Yes, but they peer using native vlan 1. The port that they connect to is layer 2. vlan 1 is a routed vlan. Unfortunately half of my network is still stuck on vlan 1. I am in the process of moving things over but it will be awhile. ONE FLAT NETWORK! Will this cause any issues on vlan 1? I have a lof of switches that are in layer 2 trunking vlans as well as about 300 other devices. (crazy i know)

lee.reade Wed, 07/16/2008 - 05:18


No this will not cause any issues, so this will give all eigrp neighbours on vlan 1 the summary address.



Giuseppe Larosa Wed, 07/16/2008 - 05:22

Hello Michael,

you can easily move the EIGRP on another vlan(s).

Just create this vlan on the VTP server or on all stub switches and hub if you don't use VTP.

Configure the L2 trunk links to carry the new vlan(s)

Configure the SVI in the 10.0/16 range on all stub routers and hub.

So you will have EIGRP neighbors on vlan 1 and the new vlan(s)

Hope to help


cowetacoit Wed, 07/16/2008 - 05:25

Giuslar, I'm limiting to what i can do because of the ISP. They are metroE and provide me a layer 2 vlan in some places. the majority of my locations are 3560's in EIGRP but there are a few small site where the ISP has installed a layer 2 switch and allowed me to plug in a small hub. I eventually want to configure a SVI and call it "EIGRP WAN" or something along those lines just to carry EIGRP routing info, like i am with vlan 1 now. Thanks for the info though

Giuseppe Larosa Wed, 07/16/2008 - 05:17

Hello Michael,

you can indeed configure an extreme summary on the L3 interface of the Hub

The default network is not needed on the stub routers.

actually, the default network is an alternate method to provide a gateway of last resort and could be used on the hub instead of the summary-address if:

the hub is connected to a major network different from or has a static route to such a different major network.


you put under router eigrp 1 a network command for that major network


ip default-network

router eigrp 1



the hub will send out EIGRP updates for net with an external flag.

the stub routers will install the net as D * and you will see a gateway of last resort set to net

However, the default-netwok wouldn't provide a reduction in the routing table of the stub routers because it just provides a default route not summarization.

You can also think of sending a summary about net 10/8. Notice multiple summary address can be configured on the same interface.

If you don't remove the static default route you will not see an eigrp default on the stub routers/switches. (lower AD). Or make them floating (use AD 200 for example)

Hope to help


cowetacoit Wed, 07/16/2008 - 05:22

Ok thanks Lee. I'll try it afterhours and see if it works.

Thanks for the info both of you. I doubt i'll configure the IP Default network. I'm trying to shrink the routing tables.


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