[j-nsp] Limit on the number of BGP communities a route can be tagged with?

[Huan Pham]

Thank you all for your replies!


For James's question, you can limit number of communities a route can be
tagged by matching "community-count"



http://www.juniper.net/techpubs/en_US/junos15.1/topics/example/policy-community-count.html

user at R1# *show policy-options*
policy-statement import-communities {
term 1 {
from {
protocol bgp;
community-count 5 orlower;
}
then accept;
}
term 2 {
then reject;
}
}






On Tuesday, August 23, 2016, James Bensley <jwbensley at gmail.com> wrote:

> On 23 August 2016 at 13:40, Olivier Benghozi
> <olivier.benghozi at wifirst.fr <javascript:;>> wrote:
> > And about a limitation to 10 communities:
> > I've seen that on SEOS (Redback/Ericsson OS for SmartEdge routers) when
> using "set community" in a route-map. This is a ridiculous arbitrary
> limitation, of course.
> >
> > Hopefully the limitation was only in the CLI, not in the BGP code
> itself. So the workaround was to use the route-map "continue" command like
> in a BASIC GOTO structure to add more communities in additional route-map
> entries (with set community additive - these are Cisco-like commands).
> >
> >> Le 23 août 2016 à 14:03, Alexander Arseniev <arseniev at btinternet.com
> <javascript:;>> a écrit :
> >>
> >> In BGP messages, a regular community is encoded in 7 bytes, and
> extended one in 11 bytes.
> >>
> >> Max BGP message size is 4096 bytes - this sets a limit for regular
> communities number to about 4K/7=570, and for extended communities to about
> 4K/11=360, if You consider the minimal mandatory information that has to be
> there apart from communities.
> >>
> >>
> >> On 23/08/2016 03:18, Huan Pham wrote:
> >>>
> >>> I remember hitting a limit on a number of communities (something like
> 10 or
> >>> so) on a platform (can not remember which one from which vendor). So I
> >>> believe that there is a hard limit a platform or OS can support.
> >>>
> >>> I test this in the lab and found no problem with tagging 100
> communities.
> >>>
> >>> Is there a maximum number of communities that Junos can tag to a
> route? If
> >>> yes, then what it is?  Thanks.
>
>
> Hi,
>
> Hopefully not completely hijacking this thread; I'm interested to know
> if there is a way I can limit a peer to a maximum number of
> communities?
>
>
> Cheers,
> James.
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