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Home > Archive > alt.certification.cisco > June 2003 > Area range command question
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Area range command question
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| I want to summarise the the following 2 subnets into 1 using ospf.
subnets :
172.16.32.0 255.255.224.0
172.16.64.0 255.255.224.0
am i right in assuming that to sumarise these into on advertisement the
address would be :
172.16.32.0 255.255.192.0
when i issue the following commands :
router ospf 100
network 172.16.32.0 0.0.31.255 area 1
network 172.16.64.0 0.0.31.255 area 1
this works ok, however if i try to sumarise the subnets using the following
command i get and inconsistent mask error message. I try the following
command
area 1 range 172.16.32.0 255.255.192
i thought that using this mask would be right as it defines a range of 64.
what am i doing wron g?
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| On Mon, 30 Jun 2003, Danny wrote:
> I want to summarise the the following 2 subnets into 1 using ospf.
>
> subnets :
> 172.16.32.0 255.255.224.0
> 172.16.64.0 255.255.224.0
>
> am i right in assuming that to sumarise these into on advertisement the
> address would be :
>
> 172.16.32.0 255.255.192.0
>
> when i issue the following commands :
>
> router ospf 100
> network 172.16.32.0 0.0.31.255 area 1
> network 172.16.64.0 0.0.31.255 area 1
>
> this works ok, however if i try to sumarise the subnets using the following
> command i get and inconsistent mask error message. I try the following
> command
>
> area 1 range 172.16.32.0 255.255.192
>
> i thought that using this mask would be right as it defines a range of 64.
>
> what am i doing wron g?
>
Try 172.16.0.0. 32 is in the middle of your range of 64.
Doan
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| 172.16.0.0/18 would cover 172.16.0.0 - 172.16.63.255 though. Then he would
be advertising a route to a subnet that is not neccessarily reachable via
that router. I think it is already summarized as far as it is going to get,
unless other subnets in the 172.16.*.0 255.255.224.0 range are reachable via
the router. FOr example, if subnet 172.16.0.0/19 AND 172.16.96.0/19 were
also reachable via his router, he could summarize that into 172.16.0.0
255.255.128.0. Thoughts?
"Doan" <doan@usc.edu> wrote in message
news:Pine.GSO.4.33.0306292352150.1115-100000@skat.usc.edu...
> On Mon, 30 Jun 2003, Danny wrote:
>
> > I want to summarise the the following 2 subnets into 1 using ospf.
> >
> > subnets :
> > 172.16.32.0 255.255.224.0
> > 172.16.64.0 255.255.224.0
> >
> > am i right in assuming that to sumarise these into on advertisement the
> > address would be :
> >
> > 172.16.32.0 255.255.192.0
> >
> > when i issue the following commands :
> >
> > router ospf 100
> > network 172.16.32.0 0.0.31.255 area 1
> > network 172.16.64.0 0.0.31.255 area 1
> >
> > this works ok, however if i try to sumarise the subnets using the
following
> > command i get and inconsistent mask error message. I try the following
> > command
> >
> > area 1 range 172.16.32.0 255.255.192
> >
> > i thought that using this mask would be right as it defines a range of
64.
> >
> > what am i doing wron g?
> >
> Try 172.16.0.0. 32 is in the middle of your range of 64.
>
> Doan
>
| |
| Hansang Bae 2003-06-30, 11:24 pm |
| In article <LYQLa.11195$0_6.972@news-binary.blueyonder.co.uk>,
dmellors@blueyonder.co.uk says...
> I want to summarise the the following 2 subnets into 1 using ospf.
> subnets :
> 172.16.32.0 255.255.224.0
> 172.16.64.0 255.255.224.0
>
> am i right in assuming that to sumarise these into on advertisement the
> address would be :
>
> 172.16.32.0 255.255.192.0
No.
>
> when i issue the following commands :
> router ospf 100
> network 172.16.32.0 0.0.31.255 area 1
> network 172.16.64.0 0.0.31.255 area 1
>
> this works ok, however if i try to sumarise the subnets using the following
> command i get and inconsistent mask error message. I try the following
> command
>
> area 1 range 172.16.32.0 255.255.192
>
> i thought that using this mask would be right as it defines a range of 64.
> what am i doing wron g?
It defines a range of 64, but not *your* range of 64. Your /18 covers
0-63, 64-127, 128-191 and 192-255. Your two subnets covers the first
range as well as the second range. You'll just have to live with the
two /19 routes.....but if you don't have anyone in the other ranges, you
can certainly summarize it. Remember, once the packet comes into the
area, summaries don't mean much. Summaries are only good for inTER area
boundaries.
--
hsb
"Somehow I imagined this experience would be more rewarding" Calvin
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