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BGP routing table entry for 128.186.0.0/16, version 5644643 Paths: (4 available, best #1)

BGP routing table entry for 128.186.0.0/16, version 5644643 Paths: (4 available, best #1) Advertised to peer-groups: AS4544-AGG-CUSTOMER-FULL 3549 209 2553 2553 2553 206.57.3.221 from 206.57.3.221 (67.17.81.103) Origin IGP, metric 90, localpref 70, valid, external, best

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BGP routing table entry for 128.186.0.0/16, version 5644643 Paths: (4 available, best #1)

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  1. BGP routing table entry for 128.186.0.0/16, version 5644643 Paths: (4 available, best #1) Advertised to peer-groups: AS4544-AGG-CUSTOMER-FULL 3549 209 2553 2553 2553 206.57.3.221 from 206.57.3.221 (67.17.81.103) Origin IGP, metric 90, localpref 70, valid, external, best Community: 4544:200 3549 209 2553 2553 2553, (received-only) 206.57.3.221 from 206.57.3.221 (67.17.81.103) ...

  2. 1 206.57.3.221 [AS 3549] 0 msec 2 67.17.67.154 [AS 3549] 24 msec 3 sjp-brdr-01.inet.qwest.net (205.171.1.85) [AS 209] 24 msec 4 svx-core-01.inet.qwest.net (205.171.214.133) [AS 209] 28 msec 5 svl-core-02.inet.qwest.net (205.171.14.77) [AS 209] 28 msec 6 205.171.21.126 [AS 209] 64 msec 7 65.114.0.54 [AS 209] 72 msecc 8 128.186.250.225 [AS 2553] 72 msec 9 128.186.6.103 [AS 2553] 76 msec

  3. 192.168.23.2 TPA AS 300 TLH AS 200 192.168.23.3 192.168.34.3 192.168.12.2 192.168.12.1 192.168.34.4 MIA AS 400 ORL AS 100 192.168.14.4 192.168.14.1

  4. R1-ORL router bgp 100 neighbor 192.168.12.2 remote-as 200 neighbor 192.168.14.4 remote-as 400 network 192.168.1.0 mask 255.255.255.0 network 192.168.10.0 mask 255.255.255.0 network 192.168.12.0 mask 255.255.255.0 network 192.168.14.0 mask 255.255.255.0

  5. R2-TLH router bgp 200 neighbor 192.168.12.1 remote-as 100 neighbor 192.168.23.3 remote-as 300 network 192.168.2.0 mask 255.255.255.0 network 192.168.20.0 mask 255.255.255.0 network 192.168.23.0 mask 255.255.255.0

  6. R3-TPA router bgp 300 neighbor 192.168.23.2 remote-as 200 neighbor 192.168.34.4 remote-as 400 network 192.168.3.0 mask 255.255.255.0 network 192.168.30.0 mask 255.255.255.0 network 192.168.34.0 mask 255.255.255.0

  7. R4-MIA router bgp 400 neighbor 192.168.14.1 remote-as 100 neighbor 192.168.34.3 remote-as 300 network 192.168.4.0 mask 255.255.255.0 network 192.168.40.0 mask 255.255.255.0

  8. clear ip bgp * • reset all my bgp peer connections • probably don’t want to resetall in production network :) • clear ip bgp N (where N is AS #) • clear ip bgp A.B.C.D (neighbor’s IP)

  9. R2-TLH#sh ip bgp summary BGP router identifier 192.168.20.1, local AS number 200 BGP table version is 17, main routing table version 17 12 network entries and 21 paths using 1920 bytes of memory 7 BGP path attribute entries using 420 bytes of memory 6 BGP AS-PATH entries using 144 bytes of memory 0 BGP route-map cache entries using 0 bytes of memory 0 BGP filter-list cache entries using 0 bytes of memory BGP activity 15/9 prefixes, 24/3 paths, scan interval 60 secs Neighbor V AS MsgRcvd MsgSent TblVer InQ OutQ Up/Down State/PfxRcd 192.168.12.1 4 100 37 35 17 0 0 00:26:21 9 192.168.23.3 4 300 34 32 17 0 0 00:26:22 9

  10. R2-TLH#sh ip bgp summary .... Neighbor V AS MsgRcvd MsgSent TblVer ... 192.168.12.1 4 100 37 35 17 0 ... 192.168.23.3 4 300 34 32 17 0 ...

  11. R2-TLH#sh ip bgp 192.168.3.0 BGP routing table entry for 192.168.3.0/24, version 10 Paths: (2 available, best #2, table Default-IP-Routing-Table) Advertised to non peer-group peers: 192.168.12.1 100 400 300 192.168.12.1 from 192.168.12.1 (192.168.10.1) Origin IGP, localpref 100, valid, external 300 192.168.23.3 from 192.168.23.3 (192.168.30.1) Origin IGP, metric 0, localpref 100, valid, external, best R2-TLH#

  12. R2-TLH#sh ip bgp BGP table version is 41, local router ID is 192.168.20.1 Status codes: s suppressed, ... Origin codes: i - IGP, e - EGP, ? - incomplete Network Next Hop ... Path *> 192.168.1.0 192.168.12.1 100 i * 192.168.23.3 300 400 100 i *> 192.168.2.0 0.0.0.0 i * 192.168.3.0 192.168.12.1 100 400 300 i *> 192.168.23.3 300 i * 192.168.4.0 192.168.12.1 100 400 i *> 192.168.23.3 300 400 i *> 192.168.10.0 192.168.12.1 100 i * 192.168.23.3 300 400 100 i

  13. R2-TLH#sh ip bgp regexp 100 400 BGP table version is 17, local router ID is 192.168.20.1 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 * 192.168.3.0 192.168.12.1 0 100 400 300 i * 192.168.4.0 192.168.12.1 0 100 400 i * 192.168.30.0 192.168.12.1 0 100 400 300 i * 192.168.34.0 192.168.12.1 0 100 400 300 i * 192.168.40.0 192.168.12.1 0 100 400 i

  14. R2-TLH#sh ip bgp regexp ^100 400$ BGP table version is 17, local router ID is 192.168.20.1 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 * 192.168.4.0 192.168.12.1 0 100 400 i * 192.168.40.0 192.168.12.1 0 100 400 i

  15. config commands to restrict announcement access-list 1 deny 192.168.20.0 0.0.0.255 access-list 1 permit 0.0.0.0 255.255.255.255 router bgp 200 neighbor 192.168.12.1 distribute-list 1 out

  16. (ROUTE NOT ADVERTISED to 192.168.12.1) R2-TLH#sh ip bgp 192.168.20.0 BGP routing table entry for 192.168.20.0/24, version 3 Paths: (1 available, best #1, table Default-IP-Routing-Table) Advertised to non peer-group peers: 192.168.23.3 Local 0.0.0.0 from 0.0.0.0 (192.168.20.1) Origin IGP, metric 0, localpref 100, weight 32768, valid, sourced, local, best

  17. (ROUTE STILL KNOWN VIA ALTERNATE PATH) R1-ORL#sh ip bgp 192.168.20.0 BGP routing table entry for 192.168.20.0/24, version 18 Paths: (1 available, best #1) Advertised to non peer-group peers: 192.168.12.2 400 300 200 192.168.14.4 from 192.168.14.4 (192.168.40.1) Origin IGP, localpref 100, valid, external, best, ref 2

  18. Filtering based on AS_PATH • quick way to make sure you are not a transit AS • ip as-path access-list 2 permit ^$ • advertise only routes this AS originates • neighbor A.B.C.D filter-list 2 out • (for all neighbors) • you still have full routes from all peers

  19. R2-TLH#sh ip bgp nei 192.168.12.1 routes BGP table version is 25, local router ID is 192.168.20.1 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 *> 192.168.1.0 192.168.12.1 0 0 100 i * 192.168.3.0 192.168.12.1 0 100 400 300 i * 192.168.4.0 192.168.12.1 0 100 400 i *> 192.168.10.0 192.168.12.1 0 0 100 i *> 192.168.12.0 192.168.12.1 0 0 100 i *> 192.168.14.0 192.168.12.1 0 0 100 i * 192.168.30.0 192.168.12.1 0 100 400 300 i * 192.168.34.0 192.168.12.1 0 100 400 300 i * 192.168.40.0 192.168.12.1 0 100 400 i Total number of prefixes 9

  20. R2-TLH#sh ip bgp nei 192.168.12.1 routes BGP table version is 33, local router ID is 192.168.20.1 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 *> 192.168.1.0 192.168.12.1 0 0 100 i *> 192.168.10.0 192.168.12.1 0 0 100 i *> 192.168.12.0 192.168.12.1 0 0 100 i *> 192.168.14.0 192.168.12.1 0 0 100 i Total number of prefixes 4

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