CIDR Aggregation Tool

Well, after observing the debates about What To Do About The Routing Table
Size, I decided to work on some informal tools to examine the current
routing table space for possible aggregations.

Right now, the raw data is the routing table from the Net Access MAE-East

It only searches for aggregates /15 < x < /25 right now - ignoring some
fairly obvious aggregation-suggestions in the /8 < x < /16 range.

The results are up at and the some of the caveats
are listed on the web page, but are:

1) When the Net Access MAE-East router has multiple identical routes that
   point to the same next-hop (192.41.177.x), the system only uses the one
   first listed in the cisco 'sho ip bgp summ' output - even though that's
   not always the 'best' route.

2) When an AS advertises both an aggregate and a specific, the specific
   is 'dropped' by the aggregator. If the input is:
   {,}, the output will be:
   {} ( will be dropped).

3) The source of data is the Net Access MAE-East router routing table,
   and we don't peer with all parties at MAE-East directly - thus, it's
   possible that the system catches aggregations that are impossible
   because they're announced to a 3rd party via different paths - but
   an informal look around doesn't appear to indicate that.

4) The system goes by next-hop rather than by AS-Path. There seems to
   be a good correlation, but ...

Also, the final disclaimer: I've examined the results and they *look*
reasonable. But I haven't written tester-tools to attempt to verify
by another algorithm that the results are correct.

Here's the table at the end of the web page:

                           Before After
                           Run Agg. Run ibm 81 68 digex 98 98 949 775 nsn.nasa 126 112 ans 2146 1425 agis 539 304 uscyber 2 2 interpath 2 2 net99 309 246 mci 2 2 mci 8963 6828 pipex 367 308 netcom 370 348 psi 1 1 icp 4499 3712 sprintlink 6429 4694 psi 1491 1098 alternet 3971 3148 96 88 122 101 suranet 470 445 internex 1 1 ios 10 8 cais 184 158 hlc 354 243 energis 2 2 delphi 3 3

A final note: We're open to {Additional static sources of route tables at
MAE-East; Additional static sources of route tables at {MAE-West, Pennsauken,
or the PacBell NAP}; and dynamic (i.e. the vty password so we can run
a sho ip bgp summ every so often) sources at any of the MAEs or NAPs.

If we get good feedback, we may automate this to run overnight and keep
a history.

Avi Freedman