[j-nsp] bgp config changes (was: autonomous-system N loops L)

Pedro Roque Marques roque at juniper.net
Fri Dec 12 02:18:15 EST 2003

bbird at epik.net writes:

> Hash: SHA1
> I also agree.
> I was informed by JTAC, this is an "artifact of the design".  Since
> JunOS creates an internal group structure, based on common
> attributes/options that affect import policy, the peers can be
> internally regrouped, so to speak.

Just a correction. It is export policy. An operational group (as
oposed to configuration template) must have a coherent export policy.

This is because BGP updates to a group are replicated among peer group
members, an export policy is evaluated only once. It is more than just
an implementation quirk. It is essential for scaling purposes.

As far as sessions resets are concerned, you can always expect a reset
if you change a parameter that is negotiated on session
establishement. Remember that the idea in JunOS is that the
operational state should always reflect the config. i.e. JunOS doesnt
leave the session in a state that doesnt match the config. While in
some cases the behaviour may be unexpected it has its advantages

I agree that in some circumstances the behaviour is less than
ideal. If you do change the export policy of the 1st (in config) order
peer of a group, the group is modified to follow the config you apply
to the 1st peer and the remaining peers in the group that do not match
its export policy are reset.

However if you deactivate the peer first and then modify its export
policy this will not happen. I hope you can use that as a workaround
while we don't get around to do something smarter in the code.

We have also been asked by several customers to document the current
behaviour bettter...


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