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Cisco Bug: CSCvt54660 - eBGP learning network from peer are advertised to the same peer

Last Modified

Apr 20, 2020

Products (1)

  • Cisco ASA 5500-X Series Firewalls

Known Affected Releases

9.10(1.218) 9.10(1.36) 9.10(1.37) 9.12(1.195) 9.12(2.175) 9.12(2.185) 9.12(2.19) 9.12(2.195) 9.12(2.20) 9.12(2.21) 9.12(2.215) 9.12(2.22) 9.12(2.23) 9.12(2.235) 9.12(3.165) 9.12(3.166) 9.12(3.180) 9.12(3.215) 9.12(3.230) 9.12(3.6) 9.12(3.7) 9.12(3.8) 9.12(3.9) 9.13(1.5) 9.13(1.6) 9.13(1.7) 9.14(0.1) 9.14(0.100) 9.14(0.101) 9.14(0.102) 9.14(0.103) 9.14(0.104) 9.14(0.105) 9.14(0.106) 9.14(0.107) 9.14(0.108) 9.14(0.109) 9.14(0.110) 9.14(0.111) 9.14(0.112) 9.14(0.113) 9.14(0.114) 9.14(0.115) 9.14(0.116) 9.14(0.70) 9.6(4.162) 9.6(4.199) 9.6(4.39) 9.6(4.40) 9.8(3.175) 9.8(4.17) 9.8(4.175) 9.8(4.18) 9.8(4.185) 9.8(4.205) 9.8(4.215) 9.8(4.220) 9.8(4.230) 9.9(2.212) 9.9(2.222) 9.9(2.66) 96.4(0.48) 96.4(0.49) 96.4(0.50) 98.4(0.23) 98.4(0.24) 98.4(0.25) 99.10(1.108) 99.10(1.109) 99.12(3.20) 99.12(3.21) 99.12(3.22) 99.12(3.23) 99.12(3.24) 99.12(3.25) 99.12(3.26) 99.12(3.27) 99.12(3.28) 99.12(3.29) 99.13(2.26) 99.13(2.27) 99.14(... 99.14(1.100) 99.14(1.101) 99.14(1.102) 99.14(1.103) 99.14(1.104) 99.14(1.105) 99.14(1.106) 99.14(1.107) 99.14(1.108) 99.14(1.109) 99.14(1.110) 99.14(1.111) 99.14(1.112) 99.14(1.113) 99.14(1.114) 99.14(1.115) 99.14(1.116) 99.14(1.117) 99.14(1.118) 99.14(1.119) 99.14(1.120) 99.14(1.121) 99.14(1.122) 99.14(1.123) 99.14(1.124) 99.14(1.125) 99.14(1.126) 99.14(1.127) 99.14(1.92) 99.14(1.93) 99.14(1.94) 99.14(1.95) 99.14(1.96) 99.14(1.97) 99.14(1.98) 99.14(1.99)

Description (partial)

Symptom:
The Cisco press BGP design guide itself states that "Transmit Side Loop Detection" is done manually because it's not the default behavior. The loop prevention is also known to be split-horizon where its implemented between iBGP but not via eBGP. The RFC itself does not dictate who (sender or receiver) should implement this.

Conditions:
When having a BGP Establishment the learned routes are being advertised to the peer again.

ASA Configuration:
router bgp 64897
 bgp log-neighbor-changes
 bgp router-id 100.71.60.83
 address-family ipv4 unicast
   neighbor 172.31.254.24 remote-as 64846
  neighbor 172.31.254.24 description 64846:CL01-P2P_Rack01/Edge_To_Rack00/Border2
  neighbor 172.31.254.24 activate
  maximum-paths 2
  maximum-paths ibgp 2
  auto-summary
  no synchronization
 exit-address-family


ASA Learned BGP Routes:
Algo(config-router-af)# show route bgp
B        172.16.24.0 255.255.255.0 [20/0] via 172.31.254.24, 01:33:08


ASA advertised routes:
Algo(config-router-af)# show bgp neighbors 172.31.254.24 advertised-routes

BGP table version is 2, local router ID is 100.71.60.83
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,
              r RIB-failure, S Stale, m multipath
Origin codes: i - IGP, e - EGP, ? - incomplete

   Network          Next Hop        Metric LocPrf Weight  Path
*> 172.16.24.0/24   172.31.254.24        0             0  64846 i
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