Mailing List Archive

BGP Maximum Prefix limit on Edge routers
Hello Gentlemen,

I wanted to ask if this is common practice to apply Maximum prefix limit on
BGP neighborship with Internet providers from where you are getting the
entire routing table. I know its consider a best practice but want to know
if its also common.
If yes, what would be the max limit of routes? Google search tells me that
the size of the routing table today is approx 800K prefixes

Thanks
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Re: BGP Maximum Prefix limit on Edge routers [ In reply to ]
Yes this is a common practice to follow for extra security measures. In
the off chance a provider starts flooding your network with more than what
is required it will safe guard your network. You can set a slightly higher
warning threshold. Usually more prevalent in MPLS environments as there
are more memory constraints on carrying Internet routes in multiple VRFs
could be detrimental to memory. Unlikely it would happen but always need
to think of better ways to safe guard your network. For as long as humans
are in existence there will always be room for error.

On Tue, Aug 11, 2020, 9:09 AM Yham <yhameed81@gmail.com> wrote:

> Hello Gentlemen,
>
> I wanted to ask if this is common practice to apply Maximum prefix limit on
> BGP neighborship with Internet providers from where you are getting the
> entire routing table. I know its consider a best practice but want to know
> if its also common.
> If yes, what would be the max limit of routes? Google search tells me that
> the size of the routing table today is approx 800K prefixes
>
> Thanks
> _______________________________________________
> cisco-nsp mailing list cisco-nsp@puck.nether.net
> https://puck.nether.net/mailman/listinfo/cisco-nsp
> archive at http://puck.nether.net/pipermail/cisco-nsp/
>
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Re: BGP Maximum Prefix limit on Edge routers [ In reply to ]
Absolutely. Make sure to add enough overhead, 25%, so you do not keep
getting warning messages in the logs.
These are the defaults for XR

To prevent a peer from flooding BGP with advertisements, a limit is
placed on the number of prefixes that are accepted from a peer for
each supported address family. The default limits can be overridden
through configuration of the maximum-prefix limit command for the peer
for the appropriate address family. The following default limits are
used if the user does not configure the maximum number of prefixes for
the address family: IPv4 Unicast: 1048576 IPv4 Labeled-unicast:
131072 IPv4 Tunnel: 1048576 IPv6 Unicast: 524288 IPv6
Labeled-unicast: 131072 IPv4 Multicast: 131072 IPv6 Multicast:
131072 IPv4 MVPN: 2097152 VPNv4 Unicast: 2097152 IPv4 MDT:
131072 VPNv6 Unicast: 1048576 L2VPN EVPN: 2097152


On Tue, Aug 11, 2020 at 9:20 AM Curtis Piehler <cpiehler2@gmail.com> wrote:

> Yes this is a common practice to follow for extra security measures. In
> the off chance a provider starts flooding your network with more than what
> is required it will safe guard your network. You can set a slightly higher
> warning threshold. Usually more prevalent in MPLS environments as there
> are more memory constraints on carrying Internet routes in multiple VRFs
> could be detrimental to memory. Unlikely it would happen but always need
> to think of better ways to safe guard your network. For as long as humans
> are in existence there will always be room for error.
>
> On Tue, Aug 11, 2020, 9:09 AM Yham <yhameed81@gmail.com> wrote:
>
> > Hello Gentlemen,
> >
> > I wanted to ask if this is common practice to apply Maximum prefix limit
> on
> > BGP neighborship with Internet providers from where you are getting the
> > entire routing table. I know its consider a best practice but want to
> know
> > if its also common.
> > If yes, what would be the max limit of routes? Google search tells me
> that
> > the size of the routing table today is approx 800K prefixes
> >
> > Thanks
> > _______________________________________________
> > cisco-nsp mailing list cisco-nsp@puck.nether.net
> > https://puck.nether.net/mailman/listinfo/cisco-nsp
> > archive at http://puck.nether.net/pipermail/cisco-nsp/
> >
> _______________________________________________
> cisco-nsp mailing list cisco-nsp@puck.nether.net
> https://puck.nether.net/mailman/listinfo/cisco-nsp
> archive at http://puck.nether.net/pipermail/cisco-nsp/
>
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