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Cisco Bug: CSCvt17690 - AS number isn't displayed in BGP-5-ADJCHANGE up/down log

Last Modified

Jun 22, 2020

Products (1)

  • Cisco Nexus 7000 Series Switches

Known Affected Releases

7.3(3)D1(1) 7.3(5)D1(1)

Description (partial)

Symptom:
(ex)2020 Feb 21 11:37:40 yuttakah %BGP-5-ADJCHANGE:  bgp- [12515] (default) neighbor 192.0.2.10 Up
- n7700-s2-dk9.7.3.3.D1.1.bin
- n7700-s2-dk9.7.3.5.D1.1.bin

On the other hands, before this version and in 8.x, we can see AS number like below.
(ex)2020 Feb 21 14:32:34 yuttakah %BGP-5-ADJCHANGE:  bgp-64497 [18560] (default) neighbor 192.0.2.10 Up
- n7700-s2-dk9.7.3.1.D1.1.bin
- n7700-s2-dk9.7.3.2.D1.1.bin
- n7700-s2-dk9.8.2.2.bin
- n7700-s2-dk9.8.2.5.bin

Very limited version is affected. I think n7700-s2-dk9.7.3.4.D1.1.bin is also affected because I had checked n7700-s2-dk9.7.3.5.D1.1.bin is affected.

Customer saw this message difference with Nexus 7000 C7018(7.3(3)D1(1) is affected(no AS number) and 7.2(2)D1(2) isn't) and I checked with above versions with Nexus7700 C7706 (6 Slot). There is no difference between 7700 and 7000.

Conditions:
Connect two ports of different N77(in our case, Eth1/9 and Eth1/25) with a Twinax cable. Then enable BGP and config BGP. In our recreate test, show run BGP of both side are as follows.

<F.11-N77-A>
feature bgp

router bgp 64496
  log-neighbor-changes
  address-family ipv4 unicast
    network 192.0.3.0/24
  neighbor 192.0.2.20 remote-as 64497
    address-family ipv4 unicast
      next-hop-self
      soft-reconfiguration inbound

<F.12-N77-B>
feature bgp

router bgp 64497
  log-neighbor-changes
  address-family ipv4 unicast
    network 192.0.2.0/24
  neighbor 192.0.2.10 remote-as 64496
    address-family ipv4 unicast
      next-hop-self
      soft-reconfiguration inbound

Then either A or B, move to "config-router-neighbor" config and do shut & no shut then check show logging log. Following is comparison of affected/non-affected versions.

--version 7.3(3)D1(1)--
yuttakah(config-router-neighbor)# show logging log | inc bgp
...
2020 Feb 21 00:35:16 yuttakah %BGP-5-ADJCHANGE:  bgp- [14850] (default) neighbor 192.0.2.10 Down - administratively shutdown
2020 Feb 21 00:35:28 yuttakah %BGP-5-ADJCHANGE:  bgp- [14850] (default) neighbor 192.0.2.10 Up

--version 8.2(2)--
yuttakah(config-router-neighbor)# show logging log | inc bgp
...
2020 Feb 24 23:36:07 yuttakah %BGP-5-ADJCHANGE:  bgp-64497 [15512] (default) neighbor 192.0.2.10 Down - administratively shutdown
2020 Feb 24 23:36:24 yuttakah %BGP-5-ADJCHANGE:  bgp-64497 [15512] (default) neighbor 192.0.2.10 Up
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