as1275

[Pedro Marques]

>>>>> "Guido" == JOIN Project Team <join@uni-muenster.de> writes:

    Guido> Hi,

    Guido> i asked Herluf Hansen (Telebit) to help us solving our
    Guido> common serious routing problem. Herluf examined our routing
    Guido> tabel and configuration in detail (thanks!) and presumed
    Guido> that our problem is caused by our BGP4+ tunnel to SWITCH. He
    Guido> said that is seems that SWITCH advertises the prefixes with
    Guido> an empty AS path.
    Guido>  When these prefixes are redistributed (by
    Guido> JOIN) 1275 is added to the AS path and that is the reason
    Guido> why it looks as if the prefixes belong to AS 1275.

Somehow i find that explanation unprobable... (not impossible but it does
seem unlikely). Switch (as559) does have one annoucement (5F04:B500::0/32)
which has as second hop as1717 and as1717 doesn't show any strange behaviour.
Also the data you supplied bellow seems to contradict this statement.

    Guido> I checked the BGP statistics to all our BGP4+ peers and only
    Guido> on the tunnel to SWITCH we have a huge among of AS loops
    Guido> (nearly every bgp msg in seems to cause a loop):

When you have a loop this means that the neighbor choose as best path a path
that as your AS in it... just that. For instance both switch and join have
a tunnel to G6... G6 may send switch paths which include your as, if switch
picks this path as best path (because you have not annouced it or because
a route is going down and it hasn't receive the withdrawn from the other
side) it'll annouce that path to you. BGP prevents the loop formation by
rejecting that path. This is just BGP doing it's thing...

But what this does show is that switch doesn't send you prefixes with an
empty AS path (empty AS paths are not in loop).

> BGP statistics at 1997-10-22 09:59:32, epoch is   0 days, 00:49:56
>  Bgp ups:                           1
>  Bgp backws:                        0
>  Bgp upd msg in:                62074
>  Bgp upd msg out:                 506
>  Bgp msg in:                    62176
>  Bgp msg out:                     583
>  Bgp notific in:                    0
>  Bgp notific out:                   0
>  AS loops:                      61921
>  Invalid Nexhops:                   0


    Guido> I stopped our BGP session to SWITCH for now.

It didn't solve the problem... I cleared the filters in one of my sessions
and i see as1275 annoucing a full bunch of routes.
BGP IPv6 table version is 8215, local router id is 192.31.7.217
Status codes: * - valid, > - best, i - internal
Origin codes: i - IGP, e - EGP, ? - incomplete

  3FFE:301:DEC1::0/48
         *> 3FFE:1100:0:C1B::1 FE80::60:3E59:4D90:E Tunnel20 1849 1225 1275 i
  3FFE:400::0/24
         *> 3FFE:1100:0:C1B::1 FE80::60:3E59:4D90:E Tunnel20 1849 1225 1275 i
  3FFE:604:2::0/48
         *> 3FFE:1100:0:C1B::1 FE80::60:3E59:4D90:E Tunnel20 1849 1225 1275 i
  3FFE:700:20:1::14/126
         *> 3FFE:1100:0:C1B::1 FE80::60:3E59:4D90:E Tunnel20 1849 1225 1275 ?
  3FFE:7C0:40::0/48
         *> 3FFE:1100:0:C1B::1 FE80::60:3E59:4D90:E Tunnel20 1849 1225 1275 i
  3FFE:D01::4/126
         *> 3FFE:1100:0:C1B::1 FE80::60:3E59:4D90:E Tunnel20 1849 1225 1275 i
  3FFE:DFE:1::4/126
         *> 3FFE:1100:0:C1B::1 FE80::60:3E59:4D90:E Tunnel20 1849 1225 1275 i
  3FFE:DFE:1::8/126
         *> 3FFE:1100:0:C1B::1 FE80::60:3E59:4D90:E Tunnel20 1849 1225 1275 i
  3FFE:DFE:1::C/126
         *> 3FFE:1100:0:C1B::1 FE80::60:3E59:4D90:E Tunnel20 1849 1225 1275 i
  3FFE:DFE:FFFE::4/126
         *> 3FFE:1100:0:C1B::1 FE80::60:3E59:4D90:E Tunnel20 1849 1225 1275 i
  3FFE:DFE:FFFE::8/126
         *> 3FFE:1100:0:C1B::1 FE80::60:3E59:4D90:E Tunnel20 1849 1225 1275 i
  3FFE:1300::0/24
         *> 3FFE:1100:0:C1B::1 FE80::60:3E59:4D90:E Tunnel20 1849 1225 1275 i
  3FFE:1400::0/24
         *> 3FFE:1100:0:C1B::1 FE80::60:3E59:4D90:E Tunnel20 1849 1225 1275 i
  3FFE:1500::FFFE:0:0:0/126
         *> 3FFE:1100:0:C1B::1 FE80::60:3E59:4D90:E Tunnel20 1849 1225 1275 i
  3FFE:1500::FFFE:0:0:4/126
         *> 3FFE:1100:0:C1B::1 FE80::60:3E59:4D90:E Tunnel20 1849 1225 1275 i
  3FFE:1500::FFFE:0:0:8/126
         *> 3FFE:1100:0:C1B::1 FE80::60:3E59:4D90:E Tunnel20 1849 1225 1275 i
  3FFE:1500::FFFE:0:0:C/126
         *> 3FFE:1100:0:C1B::1 FE80::60:3E59:4D90:E Tunnel20 1849 1225 1275 i
  3FFE:1500::FFFE:0:0:10/126
         *> 3FFE:1100:0:C1B::1 FE80::60:3E59:4D90:E Tunnel20 1849 1225 1275 i
  3FFE:1500::FFFE:0:0:14/126
         *> 3FFE:1100:0:C1B::1 FE80::60:3E59:4D90:E Tunnel20 1849 1225 1275 i
  3FFE:1500::FFFE:0:0:1C/126
         *> 3FFE:1100:0:C1B::1 FE80::60:3E59:4D90:E Tunnel20 1849 1225 1275 i
[...] and so on...

    Guido> Please can you all check whether the problem has
    Guido> disappeared.

Nope... It is still there...

  Pedro.