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Cisco Employee

Control default route advertisement in EIGRP

Hello,

I have 3 routers connected like this: r1 -> r2 -> r3

EIGRP adjacency is estabalished between r1, r2 and r2, r3.

r1 is originating default route through summary address command and I do not want r3 to receive the default route. So, I configured no default-information originate out on r2. But still R3 is getting default route via r2.

Am I missing anything here?

Regards

Sourabh

1 ACCEPTED SOLUTION

Accepted Solutions
Cisco Employee

Re: Control default route advertisement in EIGRP

Hi Sourabh,

You are setting default-network at R1, and this route is received from R2; R1 will not advertise the same route back to R2.

To test this default-network behavior, you can do

on R1

int lo0

ip add 1.1.1.1 255.0.0.0

ip default-network 1.0.0.0

router eigrp x

net 0.0.0.0

and you should see * mark for connected route 1.0.0.0/8 on R1, and * mark for eigrp route 1.0.0.0/8 on R2.

Now configure "no default-information out" on R1 to remove the default-network bit, and clear ip eigrp nei. After re-converge, R2 will not see * mark for eigrp route 1.0.0.0/8. You can achieve the same by doing "no default-information in" on R2. Remember every time you change the "default-information in/out" you need to do "clear ip eigrp nei" to make it work.

BTW, looks like you are using 15.0 code, not SRC code?

HTH,

Lei Tian

8 REPLIES
Hall of Fame Super Silver

Re: Control default route advertisement in EIGRP

Hello Sourabh,

so you have R1-R2-R3

R1 generates a default route 0.0.0.0/0 and you would like R3 to not receive it.

The command that you have given in R2 attempts to avoid R2 to locally generate a default route but does not block propagation of the default route received by R1 to R3.

you should use a distribute-list for this to perform route filtering outbound on interface to R3.

on recent IOS release like 12.4T the distribute-list command could invoke a route-map

Hope to help

Giuseppe

Cisco Employee

Re: Control default route advertisement in EIGRP

Hello Giuseppe,

So do you mean configuring no default-information out command will not allow router to generate default router.

I tried configuring this command on R1 and R1 can still generate default route and pass it to R2 and R3. Also in what scenario no default-information in command will be used then?

Regards

Sourabh

Cisco Employee

Re: Control default route advertisement in EIGRP

Hi Sourabh,

Are you using command "default information-originate" or "default-information in/ou" under eigrp process? Which code are you testing?

HTH,

Lei Tian

Cisco Employee

Re: Control default route advertisement in EIGRP

Hello Lei Tian,

I'm using 'no default-information out' under eigrp process and testing it with 12.2(33)SRC1.

Regards

Sourabh

Cisco Employee

Re: Control default route advertisement in EIGRP

Hi Sourabh,

This command is not used to advertise or block 0.0.0.0 route.

It is used when you have "ip default-network" configured; configure "default-information in" can remove the received route with candidate default-network bit, and "default-information out" can remove the candidate default-network bit when advertise out the route.

HTH,

Lei Tian

Cisco Employee

Re: Control default route advertisement in EIGRP

Hello Lei Tian,

Thanks for the clarification.

I have configured ip default-network 150.1.0.0 command on R1 and it sets the default route via R2.

R1(config-router)#do sh ip route

Gateway of last resort is 150.1.12.2 to network 150.1.0.0

S*    0.0.0.0/0 [90/30720] via 150.1.12.2, FastEthernet0/0
      1.0.0.0/8 is variably subnetted, 2 subnets, 2 masks
C        1.1.1.0/24 is directly connected, Loopback0
L        1.1.1.1/32 is directly connected, Loopback0
      2.0.0.0/24 is subnetted, 1 subnets
D        2.2.2.0 [90/156160] via 150.1.12.2, 00:01:35, FastEthernet0/0
      4.0.0.0/24 is subnetted, 1 subnets
D EX     4.4.4.0 [170/2560002816] via 150.1.12.2, 00:01:28, FastEthernet0/0
*    150.1.0.0/16 is variably subnetted, 3 subnets, 3 masks
D*       150.1.0.0/16 [90/30720] via 150.1.12.2, 00:01:35, FastEthernet0/0
C        150.1.12.0/24 is directly connected, FastEthernet0/0
L        150.1.12.1/32 is directly connected, FastEthernet0/0

Now, if I configure 'no default-information in' on R1  OR 'no default-information out' on R2, the candidate network bit will be removed hence I should not see default route on R1. But even after doing this, I see default route present on R1.

Am I still missing anything here?

Regards

Sourabh

Cisco Employee

Re: Control default route advertisement in EIGRP

Hi Sourabh,

You are setting default-network at R1, and this route is received from R2; R1 will not advertise the same route back to R2.

To test this default-network behavior, you can do

on R1

int lo0

ip add 1.1.1.1 255.0.0.0

ip default-network 1.0.0.0

router eigrp x

net 0.0.0.0

and you should see * mark for connected route 1.0.0.0/8 on R1, and * mark for eigrp route 1.0.0.0/8 on R2.

Now configure "no default-information out" on R1 to remove the default-network bit, and clear ip eigrp nei. After re-converge, R2 will not see * mark for eigrp route 1.0.0.0/8. You can achieve the same by doing "no default-information in" on R2. Remember every time you change the "default-information in/out" you need to do "clear ip eigrp nei" to make it work.

BTW, looks like you are using 15.0 code, not SRC code?

HTH,

Lei Tian

Cisco Employee

Re: Control default route advertisement in EIGRP

Hello Lei Tian,

Thanks for the help, its working now.

I'm using SRC1 an not 15.0 code.

R1#sh ip route
Codes: L - local, C - connected, S - static, R - RIP, M - mobile, B - BGP
       D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
       N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
       E1 - OSPF external type 1, E2 - OSPF external type 2
       i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2
       ia - IS-IS inter area, * - candidate default, U - per-user static route
       o - ODR, P - periodic downloaded static route, + - replicated route

Gateway of last resort is not set

*    1.0.0.0/8 is variably subnetted, 2 subnets, 2 masks
C*       1.0.0.0/8 is directly connected, Loopback0
L        1.1.1.1/32 is directly connected, Loopback0
      2.0.0.0/24 is subnetted, 1 subnets
D        2.2.2.0 [90/156160] via 150.1.12.2, 00:00:42, FastEthernet0/0
      4.0.0.0/24 is subnetted, 1 subnets
D EX     4.4.4.0 [170/2560002816] via 150.1.12.2, 00:00:39, FastEthernet0/0
      150.1.0.0/16 is variably subnetted, 3 subnets, 2 masks
C        150.1.12.0/24 is directly connected, FastEthernet0/0
L        150.1.12.1/32 is directly connected, FastEthernet0/0
D EX     150.1.24.0/24
           [170/2560002816] via 150.1.12.2, 00:00:42, FastEthernet0/0

R1#sh ver | incl IOS
Cisco IOS Software, 7200 Software (C7200-ADVIPSERVICESK9-M), Version 12.2(33)SRC1, RE
LEASE SOFTWARE (fc1)

Regards

Sourabh


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