OSPF bouncing between Cisco 4500X VSS and Nexus 9396PX VPC switch pair.
We recently moved the WAN from a 3850 stack to a 4500X VSS. There is a single VLAN between the 4500 to the Nexus switches that is used for OSPF; Very basic topology.
Ever since the change, OSPF has been bouncing at random. This has happened about 10 times over the past 2 weeks. The only thing that debugs are showing is retransmits. I can’t find any reason for this to happen. During an event they can ping each other just fine with 1472 Byte pings. No recent spanning-tree topology changes shown.
To make it even stranger, the 4500 shows that OSPF goes back to full after about a minute while the Nexus switches show they don’t go to full until 25-27 minutes later. When they come up, they do so at the same instant.
So far Cisco TAC has been scratching their head and they are no closer to resolving this case after 5 days.
Has anyone seen this before or have any insight on this? I’m grasping for straws at this point. Any show commands or configs needed to provided further assistance?
Configs:
Cisco 4500X VSS:
Code Version: cat4500e-universalk9.SPA.03.06.07.E.152-2.E7
interface Port-channel56
description Dal-DC - Nexus 9396PX pair - Device IDs: 5 & 6
switchport
switchport trunk allowed vlan 1702
switchport mode trunk
ip flow monitor NetFlow input
interface TenGigabitEthernet1/1/5
description Dal-DC1 - Nexus 9396PX - Device ID: 5 - conn to port E1/21
switchport trunk allowed vlan 1702
switchport mode trunk
ip flow monitor NetFlow input
channel-group 56 mode on
interface TenGigabitEthernet1/1/6
description Dal-DC2 - Nexus 9396PX - Device ID: 6 - conn to port E1/21
switchport trunk allowed vlan 1702
switchport mode trunk
ip flow monitor NetFlow input
channel-group 56 mode on
interface TenGigabitEthernet2/1/5
description Dal-DC1 - Nexus 9396PX - Device ID: 5 - conn to port E1/22
switchport trunk allowed vlan 1702
switchport mode trunk
ip flow monitor NetFlow input
channel-group 56 mode on
interface TenGigabitEthernet2/1/6
description Dal-DC2 - Nexus 9396PX - Device ID: 6 - conn to port E1/22
switchport trunk allowed vlan 1702
switchport mode trunk
ip flow monitor NetFlow input
channel-group 56 mode on
interface Vlan1702
description Dal-DC cross-connect for global routing
ip address 172.17.0.17 255.255.255.248
ip ospf mtu-ignore
ip ospf 1 area 2
router ospf 1
router-id 10.101.0.1
redistribute static subnets route-map Redis_Static_OSPF
redistribute bgp 393351 subnets
passive-interface Loopback0
default-information originate
Nexus SW 1:
Code Version: 7.0(3)I7(4)
vpc domain 1
peer-keepalive destination 10.11.12.10 source 10.11.12.9 vrf keepalive
peer-gateway
layer3 peer-router
interface port-channel12
description Dal-Core - Cisco 4500X VSS - Device IDs: 1 & 2
switchport mode trunk
switchport trunk allowed vlan 1702
vpc 12
interface Ethernet1/21
description Dal-Core-VSS-1 - 4500X-VSS - Device ID: 1 - conn to port 1/1/5
switchport mode trunk
switchport trunk allowed vlan 1702
channel-group 12
interface Ethernet1/22
description Dal-Core-VSS-2 - 4500X-VSS - Device ID: 2 - conn to port 2/1/5
switchport mode trunk
switchport trunk allowed vlan 1702
channel-group 12
interface Vlan1702
description Dal-Core cross-connect for global routing
no shutdown
no ip redirects
ip address 172.17.0.18/29
no ipv6 redirects
ip ospf mtu-ignore
ip router ospf 1 area 0.0.0.2
router ospf 1
router-id 10.101.0.5
redistribute static route-map Redistribute_Static
log-adjacency-changes detail
Nexus SW 2:
Code Version: 7.0(3)I7(4)
vpc domain 1
peer-keepalive destination 10.11.12.9 source 10.11.12.10 vrf keepalive
peer-gateway
layer3 peer-router
interface port-channel12
description Dal-Core - Cisco 4500X VSS - Device IDs: 1 & 2
switchport mode trunk
switchport trunk allowed vlan 1702
vpc 12
interface Ethernet1/21
description Dal-Core-VSS-1 - 4500X-VSS - Device ID: 1 - conn to port 1/1/6
switchport mode trunk
switchport trunk allowed vlan 1702
channel-group 12
interface Ethernet1/22
description Dal-Core-VSS-2 - 4500X-VSS - Device ID: 2 - conn to port 2/1/6
switchport mode trunk
switchport trunk allowed vlan 1702
channel-group 12
interface Vlan1702
description Dal-Core cross-connect for global routing
no shutdown
no ip redirects
ip address 172.17.0.19/29
no ipv6 redirects
ip ospf mtu-ignore
ip router ospf 1 area 0.0.0.2
router ospf 1
router-id 10.101.0.6
redistribute static route-map Redistribute_Static
log-adjacency-changes detail
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