Symptom
Two interfaces that have some subnet overlap both up at the same time.
Overlap condition is not properly detected and there is a conflict in NetStack.
Conditions
Configure an interface with an IP address in a large subnet and leave it shutdown.
Configure another interface with an IP address in a smaller subnet that falls under the larger subnet and leave it shutdown.
No shut the first interface.
No shut the second interface.
Both interfaces will appear to be up but the IP addressing for both will be broken in NetStack and unreachable.
See Further Problem Description section for additional details.
Workaround
Remove configuration for the interface with the larger subnet and shut/no shut the interface with the smaller subnet.
Further Problem Description
N9k-2(config)# int eth 1/39
N9k-2(config)# no switchport
N9k-2(config)# shut
N9k-2(config)# ip add 1.1.1.1/22
N9k-2(config)# int eth 1/40
N9k-2(config)# no switchport
N9k-2(config)# shut
N9k-2(config)# ip add 1.1.2.2/24
N9k-2(config)# int eth1/39 ; no shut ; int eth1/40 ; no shut
N9k-2# show logging | i netstack
2019 May 27 17:21:40 netstack: Registration with cli server complete
2019 May 27 18:07:32 N9k-2 netstack: Address 1.1.2.2 configured on Ethernet1/40(
44) already exists on Ethernet1/39(43) in ctx default(1). Deleting stale Etherne
t1/39(43), it has addr: 1.1.1.1. Addr mismatch.
2019 May 27 18:07:32 N9k-2 %NETSTACK-3-IP_FAILURE: netstack [13850] Failed to
Address(1.1.1.1) not found in ptvrf default(1), iod:43, ip_if->iod:43
N9k-2# show run interface ethernet 1/39-40
!Command: show running-config interface Ethernet1/39-40
!Time: Mon May 27 18:25:30 2019
version 7.0(3)I4(7)
interface Ethernet1/39
no switchport
ip address 1.1.1.1/22
no shutdown
interface Ethernet1/40
no switchport
ip address 1.1.2.2/24
no shutdown
N9k-2# show ip int brief
IP Interface Status for VRF "default"(1)
Interface IP Address Interface Status
Eth1/39 1.1.1.1 protocol-up/link-up/admin-up
Eth1/40 1.1.2.2 protocol-up/link-up/admin-up
