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Thanks!
So without changing the as path that comes from R9. Maybe I should change my advertisement out of R9. This way even if R6 prefers these routes through AS1 it will still advertise these routes to R4 because I did not change any local attribute within AS 567. Am I correct?
( I am not able to try this but I guess this will be correct)
Gianpietro Lavado (9/1/06 12:41 AM): > >The explanation is: when a router has two BGP possible routes, and picks one >of them, it only advertises the preferred one to its neighbors; so in this >case, when you activate the prepend, only R6 is holding the two possible >routes, and since it prefers the one that comes from AS 1, it will not >advertise the other one (from AS 9) to AS 24 or to R5. >When R6 looses the route coming from AS 1 (turning off the R1 peering), its >new preferred route is through AS 9, so it starts advertising this route to >AS 24 and R5. > >HTH > >Gianpietro > > >On 8/31/06, Ivan wrote: >> >> AS1 and AS9 announce 10.34.19.32/28 and 10.34.19.0/28 after peering with >> R1 >> shut off AS24 see path to this prefixes through AS567 and 2-a prepends. >> >> *> 10.34.19.0/28 192.168.6.6 0 567 9 9 9 i >> *> 10.34.19.32/28 192.168.6.6 0 567 9 9 9 i >> >> >> > Hi, >> > R1 AS 1 peers with R2 AS 24 >> > R2 peers with R4 AS 24 >> > R5 AS 256 and R6 AS 256 >> > >> > R5 peers with R2 in AS 24, and R6 peers with R4 in as 24 >> > >> > R6 peers to R9 in AS 9 >> > >> > Both R9 and R1 are advertising the same route. >> > >> > When I do as path prepend for the routes coming into R6 (from R9) >> these >> > routes dissappears from AS 24. >> > >> > Is this normal? If I removed the peering to R1 then the bgp routes >> comes >> > back. Any explanation why R4 is not installaing the BGP routes at the >> same >> > time at R4? I guess it has something to do with the AS Path but I need >> more >> > clarification on this matter. >> > >> > ******NO AS Path prepend at R6 yet******* >> > R4#sh ip bgp >> > BGP table version is 5, local router ID is 192.168.4.4 >> > Status codes: s suppressed, d damped, h history, * valid, > best, i - >> > internal, r RIB-failure, S Stale >> > Origin codes: i - IGP, e - EGP, ? - incomplete >> > >> > Network Next Hop Metric LocPrf Weight Path >> > * 10.34.19.0/28 192.168.6.6 0 567 9 i >> > *>i 192.168.1.1 0 100 0 1 i >> > *> 10.34.19.0/26 192.168.6.6 0 567 9 i >> > * i 192.168.5.5 0 100 0 567 9 i >> > * 10.34.19.32/28 192.168.6.6 0 567 9 i >> > *>i 192.168.1.1 0 100 0 1 i >> > *> 172.16.80.0/27 192.168.6.6 0 567 7 8 ? >> > * i 192.168.5.5 0 100 0 567 7 8 ? >> > R4# >> > *Aug 31 15:39:29.746: %BGP-5-ADJCHANGE: neighbor 192.168.6.6 Down Peer >> > closed th e session >> > *Aug 31 15:39:29.978: %BGP-5-ADJCHANGE: neighbor 192.168.6.6 Up >> > >> > **** With AS path prepend at R6***** >> > ! >> > access-list 1 permit 10.34.19.0 0.0.0.15 >> > access-list 1 permit 10.34.19.16 0.0.0.15 >> > access-list 1 permit 10.34.19.32 0.0.0.15 >> > ! >> > route-map ADDAS permit 10 >> > match ip address 1 >> > set as-path prepend 9 9 >> > ! >> > ****************************************** >> > R4#sh ip bgp >> > BGP table version is 8, local router ID is 192.168.4.4 >> > Status codes: s suppressed, d damped, h history, * valid, > best, i - >> > internal, r RIB-failure, S Stale >> > Origin codes: i - IGP, e - EGP, ? - incomplete >> > >> > Network Next Hop Metric LocPrf Weight Path >> > *>i10.34.19.0/28 192.168.1.1 0 100 0 1 i >> > *>i10.34.19.32/28 192.168.1.1 0 100 0 1 i >> > *>i172.16.80.0/27 192.168.5.5 0 100 0 567 7 8 ? >> > >> > ****Turning off the R1 peering****** >> > R4#sh ip bgp >> > BGP table version is 14, local router ID is 192.168.4.4 >> > Status codes: s suppressed, d damped, h history, * valid, > best, i - >> > internal, r RIB-failure, S Stale >> > Origin codes: i - IGP, e - EGP, ? - incomplete >> > >> > Network Next Hop Metric LocPrf Weight Path >> > *> 10.34.19.0/28 192.168.6.6 0 567 9 9 9 i >> > *> 10.34.19.0/26 192.168.6.6 0 567 9 9 9 i >> > *> 10.34.19.32/28 192.168.6.6 0 567 9 9 9 i >> > *> 172.16.80.0/27 192.168.6.6 0 567 7 8 ? >> > * i 192.168.5.5 0 100 0 567 7 8 ? >> > >> > TIA, >> > Angelo >> > >> > >> > >> > *********************** >> > No virus was detected in the attachment no filename >> > >> > Your mail has been scanned by InterScan MSS. >> > ***********-*********** >> > >> > _______________________________________________________________________ >> > Subscription information may be found at: >> > http://www.groupstudy.com/list/CCIELab.html >> >> — >> Ivan >> >> _______________________________________________________________________ >> Subscription information may be found at: >> http://www.groupstudy.com/list/CCIELab.html > >_______________________________________________________________________ >Subscription information may be found at: >http://www.groupstudy.com/list/CCIELab.html > >*********************** >No virus was detected in the attachment no filename > >Your mail has been scanned by InterScan MSS. >***********-*********** >

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