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

medrees medrees at isu.net.sa
Wed Sep 14 14:10:13 EDT 2011

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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