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BGP - distribute-list - extended ACL

 
 
davidh@wmis.net
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      10-13-2004
Hello -
Say I have the following blocks.

192.168.192.0/20
10.1.1.0/24
10.1.2.0/24

I have a distribute-list out on one of our uplinks
access-list 150 permit ip host 10.1.1.0 host 255.255.255.0
access-list 150 permit ip host 10.1.2.0 host 255.255.255.0

This tells the uplink that these ip blocks can be received through it.

Is it possible to split up the /20 though?

I tried adding
access-list 150 permit ip host 192.168.194.0 host 255.255.255.0

this does not work though. show ip bgp nei uplink-ip adver does not show 192.168.194.0/24 ... and there are no matches...

any ideas?
David

 
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MC
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      10-13-2004
I think /20 would be a 255.255.240.0 mask
<(E-Mail Removed)> wrote in message
news:(E-Mail Removed)...
> Hello -
> Say I have the following blocks.
>
> 192.168.192.0/20
> 10.1.1.0/24
> 10.1.2.0/24
>
> I have a distribute-list out on one of our uplinks
> access-list 150 permit ip host 10.1.1.0 host 255.255.255.0
> access-list 150 permit ip host 10.1.2.0 host 255.255.255.0
>
> This tells the uplink that these ip blocks can be received through it.
>
> Is it possible to split up the /20 though?
>
> I tried adding
> access-list 150 permit ip host 192.168.194.0 host 255.255.255.0
>
> this does not work though. show ip bgp nei uplink-ip adver does not show

192.168.194.0/24 ... and there are no matches...
>
> any ideas?
> David
>



 
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davidh@wmis.net
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      10-13-2004
MC <(E-Mail Removed)> wrote:
> I think /20 would be a 255.255.240.0 mask


Yes, you are correct. But I don't want to announce the whole /20.
I just want to announce a single /24 from that /20.

> <(E-Mail Removed)> wrote in message
> news:(E-Mail Removed)...
>> Hello -
>> Say I have the following blocks.
>>
>> 192.168.192.0/20
>> 10.1.1.0/24
>> 10.1.2.0/24
>>
>> I have a distribute-list out on one of our uplinks
>> access-list 150 permit ip host 10.1.1.0 host 255.255.255.0
>> access-list 150 permit ip host 10.1.2.0 host 255.255.255.0
>>
>> This tells the uplink that these ip blocks can be received through it.
>>
>> Is it possible to split up the /20 though?
>>
>> I tried adding
>> access-list 150 permit ip host 192.168.194.0 host 255.255.255.0
>>
>> this does not work though. show ip bgp nei uplink-ip adver does not show

> 192.168.194.0/24 ... and there are no matches...
>>
>> any ideas?
>> David
>>

>
>

 
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Barry Margolin
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Posts: n/a
 
      10-14-2004
In article <(E-Mail Removed)>, http://www.velocityreviews.com/forums/(E-Mail Removed) wrote:

> Hello -
> Say I have the following blocks.
>
> 192.168.192.0/20
> 10.1.1.0/24
> 10.1.2.0/24
>
> I have a distribute-list out on one of our uplinks
> access-list 150 permit ip host 10.1.1.0 host 255.255.255.0
> access-list 150 permit ip host 10.1.2.0 host 255.255.255.0
>
> This tells the uplink that these ip blocks can be received through it.
>
> Is it possible to split up the /20 though?
>
> I tried adding
> access-list 150 permit ip host 192.168.194.0 host 255.255.255.0
>
> this does not work though. show ip bgp nei uplink-ip adver does not show
> 192.168.194.0/24 ... and there are no matches...
>
> any ideas?


Do you have a route for 192.168.194.0/24 in your configuration? BGP
won't advertise a prefix that doesn't exist in its routing table.

You also need a "network 192.168.194.0 mask 255.255.255.0" statement in
your BGP configuration, or a redistribute statement to redistribute from
wherever the /24 route comes from.

--
Barry Margolin, (E-Mail Removed)
Arlington, MA
*** PLEASE post questions in newsgroups, not directly to me ***
 
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David Hill
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      10-14-2004
Barry Margolin wrote:
> In article <(E-Mail Removed)>, (E-Mail Removed) wrote:
>
>
>>Hello -
>>Say I have the following blocks.
>>
>>192.168.192.0/20
>>10.1.1.0/24
>>10.1.2.0/24
>>
>>I have a distribute-list out on one of our uplinks
>>access-list 150 permit ip host 10.1.1.0 host 255.255.255.0
>>access-list 150 permit ip host 10.1.2.0 host 255.255.255.0
>>
>>This tells the uplink that these ip blocks can be received through it.
>>
>>Is it possible to split up the /20 though?
>>
>>I tried adding
>>access-list 150 permit ip host 192.168.194.0 host 255.255.255.0
>>
>>this does not work though. show ip bgp nei uplink-ip adver does not show
>>192.168.194.0/24 ... and there are no matches...
>>
>>any ideas?

>
>
> Do you have a route for 192.168.194.0/24 in your configuration? BGP
> won't advertise a prefix that doesn't exist in its routing table.
>
> You also need a "network 192.168.194.0 mask 255.255.255.0" statement in
> your BGP configuration, or a redistribute statement to redistribute from
> wherever the /24 route comes from.
>


Is it ok to have

neighbor 192.168.192.0 mask 255.255.240.0
neighbot 192.168.194.0 mask 255.255.255.0

or should I split the /20 up into 16 class C blocks so there is no
overlapping?

- David
 
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Barry Margolin
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Posts: n/a
 
      10-14-2004
In article <(E-Mail Removed)>,
David Hill <(E-Mail Removed)> wrote:

> Barry Margolin wrote:
> > In article <(E-Mail Removed)>, (E-Mail Removed) wrote:
> >
> >
> >>Hello -
> >>Say I have the following blocks.
> >>
> >>192.168.192.0/20
> >>10.1.1.0/24
> >>10.1.2.0/24
> >>
> >>I have a distribute-list out on one of our uplinks
> >>access-list 150 permit ip host 10.1.1.0 host 255.255.255.0
> >>access-list 150 permit ip host 10.1.2.0 host 255.255.255.0
> >>
> >>This tells the uplink that these ip blocks can be received through it.
> >>
> >>Is it possible to split up the /20 though?
> >>
> >>I tried adding
> >>access-list 150 permit ip host 192.168.194.0 host 255.255.255.0
> >>
> >>this does not work though. show ip bgp nei uplink-ip adver does not show
> >>192.168.194.0/24 ... and there are no matches...
> >>
> >>any ideas?

> >
> >
> > Do you have a route for 192.168.194.0/24 in your configuration? BGP
> > won't advertise a prefix that doesn't exist in its routing table.
> >
> > You also need a "network 192.168.194.0 mask 255.255.255.0" statement in
> > your BGP configuration, or a redistribute statement to redistribute from
> > wherever the /24 route comes from.
> >

>
> Is it ok to have
>
> neighbor 192.168.192.0 mask 255.255.240.0
> neighbot 192.168.194.0 mask 255.255.255.0


I assume you meant "network" when you wrote "neighbor"

>
> or should I split the /20 up into 16 class C blocks so there is no
> overlapping?


Ideally, you should minimize the number of prefixes that you advertise,
which may require overlapping. For instance, if you want one /24 to
prefer ISP A, and everything else to use ISP B, then you would use the
two statements above -- only 2 prefixes are advertised rather than
wasting space in everyone's routing table with 16 prefixes.

--
Barry Margolin, (E-Mail Removed)
Arlington, MA
*** PLEASE post questions in newsgroups, not directly to me ***
 
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