Re: Difference between 0.0.0.0/0 and 0.0.0.0/32

Great example Ryan! What he said... : )

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 08:27:36
To: Ryan West<rwest_at_zyedge.com>; Cisco certification<ccielab_at_groupstudy.com>
Subject: Re: Difference between 0.0.0.0/0 and 0.0.0.0/32

Hi Ryan,

    Got it and thank you very much.

Regards
Anantha Subramanian Natarajan

On Mon, Sep 14, 2009 at 7:38 AM, Ryan West <rwest_at_zyedge.com> wrote:

> Anantha,
>
> This prefix-list matches all routes but the default
>
> Ip prefix-list match_all_except_my_default deny 0.0.0.0/0
> Ip prefix-list match_all_except_my_default permit 0.0.0.0/0 le 32
>
> 0.0.0.0/32 matches only the host route of 0.0.0.0 which you will most
> likely never see unless someone messed a route statement.
>
> -ryan
>
> -----Original Message-----
> From: nobody_at_groupstudy.com [mailto:nobody_at_groupstudy.com] On Behalf Of
> Anantha Subramanian Natarajan
> Sent: Monday, September 14, 2009 6:50 AM
> To: Joe Astorino; Cisco certification
> 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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> >>
> >>
> >>
> >>
> >>
> >>
> >>
> >>
> >
> >
> > --
> > 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 - 17:17:42 ART