From: OhioHondo (ohiohondo@columbus.rr.com)
Date: Fri May 09 2003 - 18:35:11 GMT-3
Mustafa
I wanted to modify my original answer in that my problem was between BGP
routers in two different sub-AS's of a confederation.
The problem however can be caused when you redistribute OSPF to BGP at more
than one point. This can cause a routing loop that makes the Best Route
change. When redisributing OSPF in an AS to BGP, care should be taken NOT to
include routes learned via any BGP to OSPF redistribution. The reason again
is that the BGP process will think these routes are locally learned and, in
lieue of any more improtant Best Route selection criteria, select these
routes as the Best Route for BGP. In the diagram below, if R2 learns an EBGP
route from R1, and then redistributes it into BGP, R2 may choose the
redistributed route as its' Best Route --- and advertise it back to R1.
EBGP -- R1 --- IBGP ---- R2
OSPF
The EBGP route redistributed from BGP to OSPF are "tagged" with the AS# that
they were learned from. You can use that tag or a variety of other methods
to define the route map (for the redistribute command) that excludes EBGP
learned routes from being redistributed into OSPF.
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com]On Behalf Of
OhioHondo
Sent: Friday, May 09, 2003 9:42 AM
To: Mustafa M Bayramov; ccielab@groupstudy.com
Subject: RE: bgp redistribution to ospf problem !
I have had this problem. The BGP Best Route keeps changing. Monitor the Best
Route for awhile and you will see it change.
When you redistribute at both points, the prefix learned from the far end
router becomes a "Locally learned route". If you do not specify some
Decision parameter that has a higher preference than (locally learned) --
i.e. Local Preference -- you can have this problem.
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com]On Behalf Of
Mustafa M Bayramov
Sent: Friday, May 09, 2003 6:42 AM
To: ccielab@groupstudy.com
Subject: bgp redistribution to ospf problem !
Hello group
Does anyone know about bug related to redistribution from EBGP to OSPF ?
RTE ----- EBGP ------ RTD-------- OSPF AREA 0 ------- RTA --------- OSPF
AREA 2 ---- RTB -------- EBGP --------- RTC
RTE advertise network Y to RTD
RTD redistribute this network to OSPF AREA 0
RTC advertise network X to RTB
RTB redistribute this network to OSPF area 2
RTA should have in OSPF database and in FIB network Y, X as external.
Well RTA see network Y, and it works, but problem arise on RTA about
network X.
RTA clears this network from FIB and OSPF database each 5 second.
The Physical layer is between RTA and RTB Ethernet.
I think it is IOS bug
Is there anyone had this problem before?
This archive was generated by hypermail 2.1.4 : Mon Jun 02 2003 - 15:13:40 GMT-3