EIGRP network 0.0.0.0 command question

localpref

I am trying to verify the follow text via a lab. This comes from a Cisco book

The other option is to use the network 0.0.0.0 EIGRP subcommand. Oddly enough, this command does not actually match interface IP addresses of interfaces, but is a special case in which IOS thinks “if my routing table has a default route in it, put a default route (0.0.0.0/0) into the EIGRP table.”
(If the route leaves the routing table, then the router will notify neighbors that the route has failed.)

My lab seems to show the exact oppsite happening it seems to match on all interfaces and not send out the default route.

Config from router I want to originate the default route from. Notice there is not a network statement for the 50.50.50.0/24 network.

router eigrp 90
network 10.1.0.0 0.0.255.255
network 172.30.0.0
network 192.168.1.0
network 0.0.0.0
no auto-summary

ip route 0.0.0.0 0.0.0.0 192.168.1.1

show command to show the default route is valid

BB#show ip route
Gateway of last resort is 192.168.1.1 to network 0.0.0.0

50.0.0.0/24 is subnetted, 1 subnets
C 50.50.50.0 is directly connected, Loopback50
S* 0.0.0.0/0 [1/0] via 192.168.1.1


routing table from a neighbor. notice he sees the 50.50.50.0/24 network and no default route. From the above statments in the book the oppsite should be happening.

R3#show ip route
Gateway of last resort is not set
50.0.0.0/24 is subnetted, 1 subnets
D 50.50.50.0 [90/10639872] via 10.1.34.1, 00:11:01, Serial0/0



Is there anyone who can help explain what is going on???

stuh84

What book is that from? That sounds like absolute rubbish to be honest. Unless its a deprecated feature of EIGRP, I just don't see how what that says could ever be the case.

localpref

It is from the CCNP ROUTE 642-902 Official Certification Guide from cisco press.

They go into some detail on this, wish I could paste the whole thing in here but think that might infringe on copywrite. Since they go into detail on how to apply this didn't think it was a typo. Any help would be much apprectiated.

Ohh if anyone has this book this can be found on page 128

Chris_

Yep, it's from the wendell odom book, he's rarely wrong! I read that chapter last week - haven't tried that in a lab yet. I'll try it tonight and see how I get on.

down77

I can check Books24x7 later but it sounds like an exercise on redistributing your default route into eigrp.

Chris_

It does sound like it's doing exactly what it says it won't though!!! Have you done a show IP protocols, I imagine it will say that your 50. Loopback will be included under eigrp.

Undy

This special case only works when your next hop is an interface. Not sure if there is any other time that this does work. Try changing your next hop for 0.0.0.0/0 to the interface 192.168.1.1 is connected to and you should see the eigrp learned route to 0.0.0.0/0 on your neighbors.

Chris_

That's a bit worrying then if your next hop isn't an interface, as in localpref's example. It seems to be using the 'network 0.0.0.0' command as a catch all to include all interfaces - which is exactly what the book says it won't do!!

Undy

I am not sure why you would use this at all to be honest, but it isn't really a catch all that causes it to advertise the 0.0.0.0/0. A network statement still shouldn't advertise your static routes. They should be redistributed.

localpref

I have confirmed that it will inject the the default route if the static is pointed towards an interface and will remove the default route if the interface goes down.

The example in the book uses an interface for its default route but no where does it state that the default route must be towards an interface.

Even when using an interface for the default route it still continues to send routes for other interfaces that do not have a specific network entires. Which by the book it should not be doing.

stuh84

This is why I don't like EIGRP, now it advertises a default route out of boredom it seems!

localpref

Chris sorry forgot to post the findings from your question. IP protocols do not show the 50.50.50.0/24 network but do show 0.0.0.0

output from show ip protocols

Routing for Networks:
10.1.0.0/16
172.30.0.0
192.168.1.0
0.0.0.0

Chris_

Thanks localpref. this is obviously one of those things that shod be forgotten after the exam!!
I'm still of the opinion that if this is a feature to advertise a default route, then it should do this without also including all local interfaces on EIGRP. Has any one else ever uses this?

localpref

Chris I am with you and as the book states that is exactly how it should work. Only injecting the default route and not being a catch all to match all interfaces.

But in pratice it doesn't work that way.

Tried to find some documentation on Cisco web site about this method to see if it was an error in the book or if it is a bug but could not find anything.

networker050184

Very interesting. Never heard about that before. You truly do learn something new every day no matter how long you have been studying this stuff.

networker050184

Very interesting. Never heard about that before. You truly do learn something new every day no matter how long you have been studying this stuff.

kryolla

I just verified it and it does inject a default and includes all interfaces in eigrp. I found it interesting so I labbed it up

Rack16R5#sh ip route stat
S* 0.0.0.0/0 is directly connected, Serial0/1


Rack16SW1#sh ip route 0.0.0.0
Routing entry for 0.0.0.0/0, supernet
Known via "eigrp 1", distance 90, metric 46137344, candidate default path, type internal
Redistributing via eigrp 1
Last update from 155.16.37.3 on FastEthernet0/3, 00:03:03 ago
Routing Descriptor Blocks:
* 155.16.37.3, from 155.16.37.3, 00:03:03 ago, via FastEthernet0/3
Route metric is 46137344, traffic share count is 1
Total delay is 1020990 microseconds, minimum bandwidth is 128 Kbit
Reliability 255/255, minimum MTU 1500 bytes
Loading 1/255, Hops 2

Rack16SW1#

Rack16R5(config)#router eigrp 1
Rack16R5(config-router)#do sh ip eigrp top 0.0.0.0
% IP-EIGRP (AS 1): Route not in topology table

Rack16R5(config-router)#net 0.0.0.0

Rack16R5(config-router)#do sh ip eigrp top 0.0.0.0
IP-EIGRP (AS 1): Topology entry for 0.0.0.0/0
State is Passive, Query origin flag is 1, 1 Successor(s), FD is 27266304
Routing Descriptor Blocks:
0.0.0.0, from Rstatic, Send flag is 0x0
Composite metric is (27266304/0), Route is Internal
Vector metric:
Minimum bandwidth is 1536 Kbit
Total delay is 999990 microseconds
Reliability is 255/255
Load is 1/255
Minimum MTU is 1500
Hop count is 0
Exterior flag is set
155.16.45.4 (Serial0/1), from 155.16.45.4, Send flag is 0x0
Composite metric is (71742208/46142464), Route is Internal
Vector metric:
Minimum bandwidth is 128 Kbit
Total delay is 2021180 microseconds
Reliability is 255/255
Load is 1/255
Minimum MTU is 1500
Hop count is 5
Exterior flag is set
Rack16R5(config-router)#

It makes it internal instead of external

APA

Very odd behaviour... interesting to know though....... good post...

What ever happened to just making use of ´ip default-network 192.168.1.0´ with EIGRP...

You have the route to 192.168.1.0/24, its a classful boundary so EIGRP will flag it as a candidate for default via the default network statement.... thus it will propagate it within the EIGRP domain, assuming your neighbors all know about 192.168.1.0/24 as well.

APA

networker050184 wrote: »

You truly do learn something new every day no matter how long you have been studying this stuff.

+1, couldn´t agree more!

ZblaJhaNi

localpref wrote: »

I am trying to verify the follow text via a lab. This comes from a Cisco book

The other option is to use the network 0.0.0.0 EIGRP subcommand. Oddly enough, this command does not actually match interface IP addresses of interfaces, but is a special case in which IOS thinks “if my routing table has a default route in it, put a default route (0.0.0.0/0) into the EIGRP table.”
(If the route leaves the routing table, then the router will notify neighbors that the route has failed.)

My lab seems to show the exact oppsite happening it seems to match on all interfaces and not send out the default route.

Config from router I want to originate the default route from. Notice there is not a network statement for the 50.50.50.0/24 network.

router eigrp 90
network 10.1.0.0 0.0.255.255
network 172.30.0.0
network 192.168.1.0
network 0.0.0.0
no auto-summary

ip route 0.0.0.0 0.0.0.0 192.168.1.1

show command to show the default route is valid

BB#show ip route
Gateway of last resort is 192.168.1.1 to network 0.0.0.0

50.0.0.0/24 is subnetted, 1 subnets
C 50.50.50.0 is directly connected, Loopback50
S* 0.0.0.0/0 [1/0] via 192.168.1.1


routing table from a neighbor. notice he sees the 50.50.50.0/24 network and no default route. From the above statments in the book the oppsite should be happening.

R3#show ip route
Gateway of last resort is not set
50.0.0.0/24 is subnetted, 1 subnets
D 50.50.50.0 [90/10639872] via 10.1.34.1, 00:11:01, Serial0/0



Is there anyone who can help explain what is going on???

Page 128 – 2nd paragraph – 4th line – middle – a sentence begins “Oddly enough, this command does not actually match interface IP addresses of interfaces, but…” – that statement is not true. The network 0.0.0.0 command actually matches all interfaces. To fix the text, delete the yellowed portion shown here.

Copied from Errata

sakayaraj20000

hi localpref,

I read the errata of the Cisco Route 642-902 certification book, and this is what i found.

Page 128 – 2^nd paragraph – 4^th line – middle – a sentence begins “Oddly enough, this command does not actually match interface IP addresses of interfaces, but…” – that statement is not true. The network 0.0.0.0 command actually matches all interfaces. To fix the text, delete the red portion shown here.

It was incorrect information given on the book. The network 0.0.0.0 command adverties all the network interfaces on that router.

Sakayaraj CCNA.

Currently studying for the CCNP Route 642-902 Exam

pham0329

Cool, you bumped a 6 months old thread to say what the guy above you said. The OP have 5 posts, all of which were from this topic back in March. I doubt he's still looking for an answer to his question.

Gngogh

sakayaraj20000 wrote: »

hi localpref,

I read the errata of the Cisco Route 642-902 certification book, and this is what i found.

Page 128 – 2^nd paragraph – 4^th line – middle – a sentence begins “Oddly enough, this command does not actually match interface IP addresses of interfaces, but…” – that statement is not true. The network 0.0.0.0 command actually matches all interfaces. To fix the text, delete the red portion shown here.

It was incorrect information given on the book. The network 0.0.0.0 command adverties all the network interfaces on that router.

Sakayaraj CCNA.

Currently studying for the CCNP Route 642-902 Exam

As i saw on a video on youtube is a shortcut for lazy people...

Dieg0M

It's actually called a "shotgun" approach. It is really usefull when you want to set up quickly a lab and test something.

Samo3411

i use it when setting labs, it work well with passive interface default , and then put no passive interface on any interface you would like to set for eigrp or ospf .

theodoxa

stuh84 wrote: »

What book is that from? That sounds like absolute rubbish to be honest. Unless its a deprecated feature of EIGRP, I just don't see how what that says could ever be the case.

It works...in Packet Tracer at least. He might try adding the static default route before entering the network 0.0.0.0 command and see if that works.