Solved: Control default route advertisement in EIGRP

souagarw · ‎03-26-2010

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

Lei Tian · ‎03-28-2010

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

View solution in original post

Giuseppe Larosa · ‎03-27-2010

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

souagarw · ‎03-27-2010

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

Lei Tian · ‎03-27-2010

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

souagarw · ‎03-27-2010

Hello Lei Tian,

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

Regards

Sourabh

Lei Tian · ‎03-27-2010

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

souagarw · ‎03-27-2010

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

Lei Tian · ‎03-28-2010

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

souagarw · ‎03-28-2010

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