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Re: Routing Table inconsistencies

  • From: Hank Nussbacher
  • Date: Tue Jun 19 01:00:35 2001

At 19:28 18/06/01 -0400, Marshall Eubanks wrote:

Hello All;

We had a problem with a domain with two different AS paths in the BGP table, so I wrote a script to
look for such problems.

There are two prefixes in the current MBGP tables here with such problems :
Go to route-views.oregon-ix.net:

route-views.oregon-ix.net>sho ip mbgp sum | excl NoNeg|Active
BGP router identifier 198.32.162.100, local AS number 6447
MBGP table version is 552946
4874 network entries and 29094 paths using 1500666 bytes of memory
658329 BGP path attribute entries using 34233108 bytes of memory
504166 BGP AS-PATH entries using 12495820 bytes of memory
408 BGP community entries using 10324 bytes of memory
27226 BGP filter-list cache entries using 435616 bytes of memory
Dampening enabled. 62 history paths, 3305 dampened paths
BGP activity 391384/274126 prefixes, 54115708/50018963 paths

Neighbor V AS MsgRcvd MsgSent TblVer InQ OutQ Up/Down State/PfxRcd
129.250.0.6 4 2914 1974401 36393 552946 0 0 4d09h 3936
129.250.0.11 4 2914 1378596 36399 552946 0 0 1w6d 3936
155.229.0.36 4 4565 122639 30255 552946 0 0 1w5d 23
198.32.8.252 4 11537 136322 36119 552946 0 0 1w3d 3543
203.181.248.242 4 7660 189814 71618 552946 0 0 05:34:54 1863
204.42.253.253 4 267 1251009 36379 552946 0 0 1w6d 3941
204.212.44.131 4 234 979924 36399 552946 0 0 1w6d 3938
205.215.45.50 4 4006 3332093 55271 552946 0 0 5d16h 2738
206.220.240.222 4 10764 2326042 69592 552946 0 0 05:33:12 4760
216.140.2.63 4 6395 1776339 36347 552946 0 0 4d20h 118
216.140.8.63 4 6395 1598580 36337 552946 0 0 4d20h 118
216.140.14.127 4 6395 1631400 36135 552946 0 0 3d19h 118

A simple count via:
route-views.oregon-ix.net>sho ip mbgp inc | incl >
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal
*> 129.250.0.11 5 0 2914 3549 i
*> 206.220.240.222 0 10764 145 195 i
*> 206.220.240.222 0 10764 145 195 i
*> 206.220.240.222 0 10764 145 195 i
*> 129.250.0.6 22 0 2914 i
*> 129.250.0.11 16 0 2914 1800 i
*> 129.250.0.6 22 0 2914 i
*> 129.250.0.11 16 0 2914 i
*> 129.250.0.11 16 0 2914 i
*> 129.250.0.11 9 0 2914 i
*> 129.250.0.11 12 0 2914 i
*> 129.250.0.11 5 0 2914 i
*> 129.250.0.11 8 0 2914 i
*> 129.250.0.11 9 0 2914 i
*> 206.220.240.222 0 10764 145 195 i
*> 206.220.240.222 0 10764 145 195 i

shows 16 prefixes that are inconsistent AS origin within the MBGP tables (if anyone knows the reg-exp for seeing the actual prefixes - 1 per line and not just the best path - I'd like to know :-)). As we see in the larger BGP tables (close to 500 inconsistent ASs), not too many ISPs care about this.

-Hank


 Date of BGP Dump  Mon Jun 18 15:39:46 EDT 2001

 ROUTING INCONSISTENCY Detected for Prefix =  198.9.201.0       :

*> 198.9.201.0      160.81.38.225           75             0 1239 10888 i
*                   204.147.129.89                         0 145 24 i

 ROUTING INCONSISTENCY Detected for Prefix =  198.9.202.0       :

*  198.9.202.0      204.147.129.89                         0 145 24 i
*>                  160.81.38.225           75             0 1239 10888 i

And a total of 488 prefixes in the BGP tables with such problems !!!!!

The complete lists are contained in

http://www.multicasttech.com/status/mbgp.inconsistency and
http://www.multicasttech.com/status/bgp.inconsistency

I could update these regularly if there was any demand.

I may be obtuse, but I cannot see how this could be a good thing.

                                 Regards
                                 Marshall Eubanks



T.M. Eubanks
Multicast Technologies, Inc
10301 Democracy Lane, Suite 410
Fairfax, Virginia 22030
Phone : 703-293-9624       Fax     : 703-293-9609
e-mail : tme@multicasttech.com
http://www.on-the-i.com

Test your network for multicast : http://www.multicasttech.com/mt/
 Check the status of multicast in real time :
 http://www.multicasttech.com/status/index.html




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