[j-nsp] Difference between (AS-Path, as-override, Loops) juniper & Cisco !!!

Krasimir Avramski krasi at smartcom.bg
Fri Sep 16 11:28:39 EDT 2011


You can disable this sanity check by reverting to an really old behavior
with:
advertise-peer-as in bgp. Without as-override enabled this will delegate
as-loop responsibility to CPE.

Regards,
Krasi

On Wed, Sep 14, 2011 at 9:10 PM, medrees <medrees at isu.net.sa> wrote:

> Hi Experts
>
>       Firstly, I want to explain the difference between Cisco & Juniper
> regarding the as-path attribute in BGP routes and how they overcome the
> routing loops for BGP routing between PE-CE.
>
> Cisco : send the BGP routes to the EBGP neighbor and the checking of the
> as-path attribute is responsibility of received neighbor and  if the
> received as-path include the local AS number the route is rejected so that
> the (allow-as in) feature can override this action in the local router or
> (as-override) feature in the sender EBGP neighbor's router.
>
> Juniper: Before sending the BGP route the sender check the as-path
> attribute
> and if it include AS number of the received neighbor it won't send the
> route, so that the (As-override) feature is an option to allow this routes
> to be sent but there isn't meaning for (loops ) feature which equivalent to
> (Cisco allow-as in) feature where the route won't be received unless sender
> check no routing loops may occur.
>
> So that, in juniper no need for (loops) command, or SOO where even if there
> is backdoor link in CE multi-homed site for the same reason (the PE or the
> sender always check the BGP routes as-path before sending it).
>
> Thanks in advance for your support
>
> Best Regards,
> Mohamed Edrees
>
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