I'm soliciting suggestions on the pros and cons on the assortment of
ways to inject customer routes into iBGP at the edge.
One could simply reference prefix-lists in the BGP config on a
per-neighbor basis (or peer-group). The downside to this is that
prefix-lists can't haven't inline comments for storing information about
the individual prefixes. As the prefixes on the edge grow I would think
that admin overhead and potential for errors would grow as well.
I could reference route-maps in the BGP config as well (per
neighbor/peer-group). I'm doing this today, matching against a
prefix-list to get my routes. The upside is I add a new sequence to the
route-map per customer and create a uniquely-named prefix-list per
customer. This of course requires more config and more potential typos
but makes changes as customers come and go much more clearcut (ie, there
is no question which prefixes belong to which customer). Another upside
is that I can also put specific communities on prefixes with a
route-map. I'm not doing this today but I plan to in the future as my
BGP community design progresses.
A third option is redistributing statics into BGP. This gives me the
opportunity to tag specific prefixes and filter them with a route-map so
I only redistribute the prefixes that I want redistributed. I can also
name static routes. I need a static route anyway to tack up the route
for outbound advertisement and to prevent loops. The downside is that I
hate using redistribution. I'm not a big fan of it. I've been bit too
many times to consider redistribution a good method of doing anything.
It will also result in higher CPU load as the RIB is frequently parsed
for statics and processed with the route-map if I'm not mistaken.
Correct?
A fourth option would be to use distribute-lists. I can use remarks to
label my individual prefixes in the ACL which is good but I end up with
one large distribute-list ACL for all my customer prefixes. That means
any errors could affect all customers at once. I also don't end up
using route-maps so I don't get to set communities on advertised prefixes.
And finally I could use a combination of any of the above to accomplish
my goals.
What methods do my SP colleagues prefer to use when managing the
injection of customer routes into iBGP? I'm open to suggestions. I've
tried both of the first 2 options and lean towards the 2nd. It's time I
get the remaining customer routes out of the IGP but unfortunately I
can't see far enough ahead to decide which method is best. I can't help
but to think that there must be a better way to accomplish my goals
without increasing my work load too much and without increasing the
likelihood of making major mistakes.
Thanks
Justin
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