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Cisco Bug: CSCum56372 - N3K: BGP Route Updates Delayed With Prefix-Peers and No Est. Neighbors

Last Modified

Mar 16, 2016

Products (6)

  • Cisco Nexus 3000 Series Switches
  • Cisco Nexus 3064 Switch
  • Cisco Nexus 3016 Switch
  • Cisco Nexus 3064-T Switch
  • Cisco Nexus 3048 Switch
  • Cisco Nexus 3132Q Switch

Known Affected Releases

5.0(3)U5(1f) 6.0(2)U2(1) 6.0(2)U2(2Z)

Description (partial)

Symptom:
BGP updates will not be sent, and received updates will not be installed till 90+ seconds after BGP session establishes.

Conditions:
This is only observed when we have BGP prefix-peers configured and there are no established BGP sessions in all of the BGP prefix-peer groups configured. 

For example, in the following snippet we have one prefix-peer group configured and one static neighbor. If there are no established peers in the prefix-peer group, then after BGP is established there will be a 90+ second delay for this host to advertise prefixes to neighbors via BGP and to install learnt BGP routes into RIB

router bgp A
  address-family ipv4 unicast
    network <network>
  neighbor a.b.c.d remote-as B
    address-family ipv4 unicast
  neighbor w.x.y.z/24
    remote-as C
    address-family ipv4 unicast

If there is an established peer in w.x.y.z/24 range then this issue will not be seen. Or we can have another prefix-peer group which has an established neighbor in it.
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