[c-nsp] BGP Peer Group drawbacks???

[Marko Milivojevic]

> Seems to me that peer/session templates would allow you to get more granular
> with your BGP configuration then peer-groups due to
> their inheritance feature.  So it makes sense to me.
>
> I don't think scale is the only deciding factor between peer group and
> templates.  I think it also depends on the complexity of your routing policy
> and # of prefix's etc...I guess a question could be - why wouldn't you use
> templates - even for a simple BGP config?  Any ISP ops on the list - do you
> use templates, peer-groups - or both?
>
> To the original poster - perhaps you can decide for yourself?  See here:
> http://www.cisco.com/en/US/docs/ios/12_0s/feature/guide/s_bgpct.html#wp1027129
> and
> a good explanation here with configurations
> http://cciethebeginning.wordpress.com/2009/01/09/358/

Well... comparing peer-groups and templates is just a little bit like
comparing apples and oranges. They were meant to solve different
problems.

When they were introduced, peer-groups were used to optimize the
updates sent to neighbors. I.e. using peer-groups had impact on your
CPU in such a way that members of the same peer group shared the same
update that was only replicated. Non-peer-group peers had to have
their updates built separately, even though it may end up being the
same. The fact that the peer-groups had this nice side effect of being
able to group configuration and make deployments somewhat easier, was
never their primary purpose in life... and that shows, as they look
unnatural and are not very flexible.

Naturally, over the years, Cisco found the way to optimize updates
automatically (using update-groups) and the only purpose of
peer-groups was to group commands together. Since they were not doing
that as well as one would hope (whoever configured peer-groups in
multiple address-families probably knows how ... "intuitive" that is),
another solution needed to be made. This is how we got templates,
whose only purpose is to group configurations and they do pretty good
job at that.

All that said, for all new deployments, I would suggest using
templates and not peer-groups... they could disappear at any time.

--
Marko Milivojevic - CCIE #18427
Senior Technical Instructor - IPexpert

Mailto: markom at ipexpert.com
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