I have 3 C9300 Switches configured to use ISIS running 17.12.04 issue was present on 17.06.04 prior to upgrade as well. Each of the switches is configured for the same ISIS area with different SystemID's based upon the switches Loopback0 interface IP. The VLAN1 SVI is being used for ISIS adjacency. My ISIS adjacencies come up but are flapping frequently with the following errors:
%CLNS-3-BADPACKET: ISIS: LAN L2 hello, Duplicate system ID detected from 9c09.8b3f.2b47 (Vlan1)
%CLNS-3-BADPACKET: ISIS: LAN L2 hello, Duplicate system ID detected from 9c09.8b3f.38c7 (Vlan1)
%CLNS-3-BADPACKET: ISIS: LAN L1 hello, Duplicate system ID detected from 9c09.8b3f.4247 (Vlan1)
NOTE: These errors are seen for L1 and L2 both and are occurring right around the same time on all devices.
The SystemID in the errors is the MAC address of the local VLAN1 interface on each of these switches.
I am not seeing any L2 loops and these switches are single uplinked i.e. no redundant connections between them:
SW1 -> SW2 -> SW3
SW1:
router isis
net 49.0000.0100.3109.6010.00
authentication mode md5 level-1
authentication mode md5 level-2
authentication key-chain isis-keys level-1
authentication key-chain isis-keys level-2
metric-style wide
max-lsp-lifetime 65535
lsp-refresh-interval 65000
spf-interval 5 1 20
prc-interval 5 1 20
lsp-gen-interval 5 1 20
no hello padding multi-point
log-adjacency-changes
nsf ietf
default-information originate
bfd all-interfaces
interface Vlan1
ip address 10.0.96.2 255.255.255.0
ip lisp source-locator Loopback0
ip router isis
load-interval 30
bfd interval 500 min_rx 500 multiplier 3
no bfd echo
clns mtu 1400
interface Loopback0
ip address 10.31.96.10 255.255.255.255
ip router isis
clns mtu 1400
end
SW2:
router isis
net 49.0000.0100.3109.6020.00
authentication mode md5 level-1
authentication mode md5 level-2
authentication key-chain isis-keys level-1
authentication key-chain isis-keys level-2
metric-style wide
max-lsp-lifetime 65535
lsp-refresh-interval 65000
spf-interval 5 1 20
prc-interval 5 1 20
lsp-gen-interval 5 1 20
no hello padding multi-point
log-adjacency-changes
nsf ietf
bfd all-interfaces
interface Vlan1
ip address 10.0.96.3 255.255.255.0
ip lisp source-locator Loopback0
ip router isis
load-interval 30
bfd interval 500 min_rx 500 multiplier 3
no bfd echo
clns mtu 1400
interface Loopback0
ip address 10.31.96.20 255.255.255.255
ip router isis
clns mtu 1400
SW3:
router isis
net 49.0000.0100.3109.6021.00
authentication mode md5 level-1
authentication mode md5 level-2
authentication key-chain isis-keys level-1
authentication key-chain isis-keys level-2
metric-style wide
max-lsp-lifetime 65535
lsp-refresh-interval 65000
spf-interval 5 1 20
prc-interval 5 1 20
lsp-gen-interval 5 1 20
no hello padding multi-point
log-adjacency-changes
nsf ietf
bfd all-interfaces
interface Vlan1
ip address 10.0.96.4 255.255.255.0
ip lisp source-locator Loopback0
ip router isis
load-interval 30
bfd interval 500 min_rx 500 multiplier 3
no bfd echo
clns mtu 1400
interface Loopback0
ip address 10.31.96.21 255.255.255.255
ip router isis
clns mtu 1400
Back to the L2 loop discussion, only trunk ports where vlan1 is allowed are the uplinks between devices, all uplinks are also STP loopguard enabled and I'm not seeing any errors here. Packet counters on all interfaces are showing clean.
Does anyone one have any ideas as to what could be causing these errors?
