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
router.
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 http://routes.netaxs.com 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:
{205.89.10.128/17, 205.89.10.130}, the output will be:
{205.89.10.128/17} (205.89.10.130 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
192.41.177.110 ibm 81 68
192.41.177.115 digex 98 98
192.41.177.120 eu.net 949 775
192.41.177.125 nsn.nasa 126 112
192.41.177.140 ans 2146 1425
192.41.177.145 agis 539 304
192.41.177.150 uscyber 2 2
192.41.177.160 interpath 2 2
192.41.177.170 net99 309 246
192.41.177.180 mci 2 2
192.41.177.181 mci 8963 6828
192.41.177.190 pipex 367 308
192.41.177.210 netcom 370 348
192.41.177.235 psi 1 1
192.41.177.240 icp 4499 3712
192.41.177.241 sprintlink 6429 4694
192.41.177.245 psi 1491 1098
192.41.177.249 alternet 3971 3148
192.41.177.251 es.net 96 88
192.41.177.252 es.net 122 101
192.41.177.6 suranet 470 445
192.41.177.70 internex 1 1
192.41.177.80 ios 10 8
192.41.177.85 cais 184 158
192.41.177.86 hlc 354 243
192.41.177.89 energis 2 2
192.41.177.95 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
freedman@netaxs.com