From: Brian McGahan (brian@cyscoexpert.com)
Date: Tue Feb 18 2003 - 20:35:47 GMT-3
Syv,
The synchronization rule only applies to iBGP learned prefixes.
It states that an iBGP learned prefix cannot be considered best unless
you have a matching IGP route for that BGP prefix.
HTH
Brian McGahan, CCIE #8593
Director of Design and Implementation
brian@cyscoexpert.com
CyscoExpert Corporation
Internetwork Consulting & Training
Toll Free: 866-CyscoXP
Outside US: 847.674.3392
Fax: 847.674.2625
> -----Original Message-----
> From: Syv Ritch [mailto:syv@911networks.com]
> Sent: Tuesday, February 18, 2003 4:57 PM
> To: Brian McGahan
> Subject: Re[2]: BGP & Route reflectors
>
> On Tuesday, February 18, 2003, Brian McGahan wrote:
>
> I think that I must be lost. By doing the no sync onto C it
> works.
>
> On B: I have both reachability & synchronization.
>
> B does the eBGP connection, and should inject the route into
> C, so C should not need to have the synchronization rule?
> It's iBGP to iBGP.
>
> What am I missing?
>
>
> -----Original Message-----
> BM> Syv,
>
> BM> The two most common reasons for a route not being best in
the
> BM> BGP table are:
>
> BM> 1. you don't have reachability to the next-hop address
> BM> 2. the synchronization rule is not met.
>
> BM> Ensure that C has a route to 10.108.44.44. If not, you
cannot
> BM> consider the route to be best.
>
> BM> The synchronization rule states that for all iBGP learned
> BM> prefixes, you must have a matching IGP route in order to consider
it
> BM> best. In addition to this, if the IGP used to synchronize is
OSPF,
> the
> BM> router-id of the BGP neighbor you are learning the prefix from and
the
> BM> router-id of the originator into the OSPF domain must match. If
all
> BM> routers in the transit path are running BGP, you could also just
turn
> BM> synch off with the BGP command 'no synchronization'.
>
> BM> For more info on the BGP decision process:
>
> BM>
>
http://www.cisco.com/en/US/tech/tk648/tk365/technologies_tech_note09186a
> BM> 0080094431.shtml
>
>
> BM> HTH
>
> BM> Brian McGahan, CCIE #8593
> BM> Director of Design and Implementation
> BM> brian@cyscoexpert.com
>
> BM> CyscoExpert Corporation
> BM> Internetwork Consulting & Training
> BM> Toll Free: 866.CyscoXP
> BM> Fax: 847.674.2625
>
>
> >> -----Original Message-----
> >> From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On
Behalf
> BM> Of
> >> Syv Ritch
> >> Sent: Tuesday, February 18, 2003 3:03 PM
> >> To: ccielab@groupstudy.com
> >> Subject: BGP & Route reflectors
> >>
> >> Hi,
> >>
> >> A [eBGP] --> B [RR client] --> C [Route Reflector] --> D [RR
client]
> >>
> >> A is connected to the client and not to the route reflector.
> >> How do I propagate the route 10.108.144.0 from A:
> >>
> >> Router B:
> >>
> >> TS-2512#b
> >> BGP table version is 3, local router ID is 99.99.99.99
> >> Status codes: s suppressed, d damped, h history, * valid, > best, i
-
> >> internal
> >> Origin codes: i - IGP, e - EGP, ? - incomplete
> >>
> >> Network Next Hop Metric LocPrf Weight Path
> >> * i10.108.122.0/24 10.108.22.22 0 100 0 65110
i
> >> * i10.108.133.0/24 10.108.33.33 0 100 0 i
> >> *> 10.108.144.0/24 10.108.44.44 0 0 65244
i
> >> * i10.108.155.0/24 10.108.22.22 100 0 65110
i
> >> * i10.108.166.0/24 10.108.22.22 100 0 65110
i
> >> *> 10.108.199.0/24 0.0.0.0 0 32768 i
> >>
> >> Router C:
> >>
> >> c1720#b
> >> BGP table version is 5, local router ID is 33.33.33.33
> >> Status codes: s suppressed, d damped, h history, * valid, > best, i
-
> >> internal
> >> Origin codes: i - IGP, e - EGP, ? - incomplete
> >>
> >> Network Next Hop Metric LocPrf Weight Path
> >> *> 10.108.122.0/24 10.108.22.22 0 0 65110
i
> >> *> 10.108.133.0/24 0.0.0.0 0 32768 i
> >> * i10.108.144.0/24 10.108.44.44 0 100 0 65244
i
> >> *> 10.108.155.0/24 10.108.22.22 0 65110
i
> >> *> 10.108.166.0/24 10.108.22.22 0 65110
i
> >> * i10.108.177.0/24 10.108.77.77 0 100 0 i
> >> * i10.108.199.0/24 10.108.99.99 0 100 0 i
> >>
> >> 10.108.144.0 is i and not *>
> >>
> >> Router D:
> >>
> >> c1602r#b
> >> BGP table version is 2, local router ID is 77.77.77.77
> >> Status codes: s suppressed, d damped, h history, * valid, > best, i
-
> >> internal
> >> Origin codes: i - IGP, e - EGP, ? - incomplete
> >>
> >> Network Next Hop Metric LocPrf Weight Path
> >> * i10.108.122.0/24 10.108.22.22 0 100 0 65110
i
> >> * i10.108.133.0/24 10.108.33.33 0 100 0 i
> >> * i10.108.155.0/24 10.108.22.22 100 0 65110
i
> >> * i10.108.166.0/24 10.108.22.22 100 0 65110
i
> >> *> 10.108.177.0/24 0.0.0.0 0 32768 i
> >>
> >> No 10.108.144.0
> >>
> >> --
> >> Thanks
> >> syv@911networks.com
>
>
>
> --
> Thanks
> syv@911networks.com
> When the network has to work
This archive was generated by hypermail 2.1.4 : Sat Mar 01 2003 - 11:06:27 GMT-3