Re: Difference between 0.0.0.0/0 and 0.0.0.0/32

Hey,

No, as you can see in the test 0.0.0.0/32 does NOT match all routes OR the default...it would match 0.0.0.0 with a mask of 255.255.255.255 which is not the default route

Regards,

Joe Astorino - CCIE #24347 R&S
Technical Instructor - IPexpert, Inc.
Cell: +1.586.212.6107
Fax: +1.810.454.0130
Mailto: jastorino_at_ipexpert.com

-----Original Message-----
From: Anantha Subramanian Natarajan <anantha.natarajan_at_gravitant.com>

Date: Mon, 14 Sep 2009 05:50:03
To: Joe Astorino<jastorino_at_ipexpert.com>; Cisco certification<ccielab_at_groupstudy.com>
Subject: Re: Difference between 0.0.0.0/0 and 0.0.0.0/32

Hi Joe,

   Awesome !!!!!!//Thank you very much

   So based on your test and explanation,is my understanding right that,
0.0.0.0/32 matches all routes *except *default route.Please correct me if I
am wrong in understanding

Once again thank you for your time

Regards
Anantha Subramanian Natarajan

On Mon, Sep 14, 2009 at 12:57 AM, Joe Astorino <jastorino_at_ipexpert.com>wrote:

> 0.0.0.0/0 le 32 <--- This matches ANY route. Basically the logic here is
> "0 bits must match AND the subnet mask can be anything <= 32 bits (anything
>
> 0.0.0.0/0 <--- This matches ONLY the default route. The logic here is
> that we are matching EXACTLY 0.0.0.0 with a mask of 0.0.0.0. Nothing more,
> nothing less.
>
> 0.0.0.0/32 <--- Logically, this would match EXACTLY 0.0.0.0 with a mask of
> 255.255.255.255. From my testing (see below) this does *NOT* match every
> route. You will have to excuse the fact that tonight I have been playing
> with VRFs...
>
>
> *BEFORE applying the prefix-list called from a distribute-list in OSPF...
> *
> R1(config-router)#do sh ip route vrf VRF1 ospf
>
> Routing Table: VRF1
>
> 2.0.0.0/32 is subnetted, 1 subnets
> O 2.2.2.2 [110/2] via 100.100.12.2, 00:01:39, FastEthernet0/0.12
> 100.0.0.0/8 is variably subnetted, 6 subnets, 2 masks
> O 100.100.56.0/24
> [110/66] via 100.100.12.2, 00:01:39, FastEthernet0/0.12
> O 100.100.200.2/32
> [110/1] via 100.100.12.2, 00:01:39, FastEthernet0/0.12
> O 100.100.200.4/32
> [110/65] via 100.100.12.2, 00:01:39, FastEthernet0/0.12
> O 100.100.200.5/32
> [110/65] via 100.100.12.2, 00:01:39, FastEthernet0/0.12
> O 100.100.200.6/32
> [110/65] via 100.100.12.2, 00:01:39, FastEthernet0/0.12
> 4.0.0.0/32 is subnetted, 1 subnets
> O 4.4.4.4 [110/66] via 100.100.12.2, 00:01:39, FastEthernet0/0.12
> 5.0.0.0/32 is subnetted, 1 subnets
> O 5.5.5.5 [110/66] via 100.100.12.2, 00:01:39, FastEthernet0/0.12
> 6.0.0.0/32 is subnetted, 1 subnets
> O 6.6.6.6 [110/66] via 100.100.12.2, 00:01:39, FastEthernet0/0.12
> 7.0.0.0/32 is subnetted, 1 subnets
> O 7.7.7.7 [110/67] via 100.100.12.2, 00:01:42, FastEthernet0/0.12
>
>
> *Now, we create and apply the prefix-list...*
>
> ip prefix-list foo seq 5 permit 0.0.0.0/32
>
> *Apply to the OSPF process and check the routing table...*
>
> R1(config)#router ospf 1
> R1(config-router)#distribute-list prefix foo in
> R1(config-router)#do sh ip route vrf VRF1 ospf
>
> Routing Table: VRF1
>
> *You see we have NO OSPF learned routes...and that below the entire
> routing table shows only connected routes...*
>
> R1(config-router)#do sh ip route vrf VRF1
>
> Routing Table: VRF1
> Codes: 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
>
> Gateway of last resort is not set
>
> 1.0.0.0/32 is subnetted, 1 subnets
> C 1.1.1.1 is directly connected, Loopback1
> 100.0.0.0/24 is subnetted, 1 subnets
> C 100.100.12.0 is directly connected, FastEthernet0/0.12
>
>
>
>
>
>
>
> On Mon, Sep 14, 2009 at 1:02 AM, Anantha Subramanian Natarajan <
> anantha.natarajan_at_gravitant.com> wrote:
>
>> Hi Khurram,
>>
>> Thank you for clarifying .....So 0.0.0.0/0 le 32 is equal to 0.0.0.0/32?
>>
>> Thank You
>>
>> Regards
>> Anantha Subramanian Natarajan
>>
>> On Sun, Sep 13, 2009 at 11:59 PM, Khurram Noor <
>> engr.khurramnoor_at_googlemail.com> wrote:
>>
>> > 0.0.0.0/0 means (0.0.0.0 0.0.0.0) only default route where as
>> 0.0.0.0/32means (0.0.0.0 255.255.255.255) all routes.
>> >
>> >
>> > --
>> > Khurram Noor
>> > CCIE # 24419
>> >
>> > http://www.linkedin.com/in/khurramnoor
>>
>>
>> Blogs and organic groups at http://www.ccie.net
>>
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>>
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>>
>>
>>
>
>
> --
> Regards,
>
> Joe Astorino - CCIE #24347 R&S
> Technical Instructor - IPexpert, Inc.
> Cell: +1.586.212.6107
> Fax: +1.810.454.0130
> Mailto: jastorino_at_ipexpert.com

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Received on Mon Sep 14 2009 - 17:16:27 ART