Interface flapping and always shows up/up even other side is shutdown

bluejays · ‎06-30-2005

Hi, there, I have a interface flapping issue in my network. 2 Cat3560 is connected through 2 trunk port configured with port-channel. When I shutdown one of port in Vlan100, other 2 ports in the same vlan will flap going up and down and OSPF will lose the neighbor. One thing I notice that is when I shutdown the switch port, on the other side of router, the L1-L2 is still up/up. I think it should be up/down. I have a keepalive setting on the router interface to 1800. Any body can give me some hints here to troubleshoot?

Here is the switch configs.

Building configuration...

no service pad

ip subnet-zero

ip routing

!

no ip domain-lookup

!

spanning-tree mode pvst

no spanning-tree optimize bpdu transmission

spanning-tree extend system-id

!

interface Port-channel1

switchport trunk encapsulation dot1q

switchport trunk native vlan 999

switchport trunk allowed vlan 100,200,300,400,600,700

switchport mode trunk

!

interface GigabitEthernet0/1

switchport access vlan 600

speed 100

duplex full

!

interface GigabitEthernet0/2

switchport access vlan 100

speed 100

duplex full

!

interface GigabitEthernet0/3

switchport access vlan 600

speed 100

duplex full

!

interface GigabitEthernet0/4

switchport access vlan 700

speed 100

duplex full

!

interface GigabitEthernet0/5

switchport access vlan 700

speed 100

duplex full

!

interface GigabitEthernet0/6

switchport access vlan 100

speed 100

duplex full

!

interface GigabitEthernet0/7

switchport access vlan 100

speed 100

duplex full

!

interface GigabitEthernet0/8

switchport access vlan 100

!

interface GigabitEthernet0/9

switchport access vlan 100

speed 100

duplex full

!

interface GigabitEthernet0/10

switchport access vlan 100

speed 100

duplex full

!

interface GigabitEthernet0/11

switchport access vlan 100

speed 100

duplex full

!

interface GigabitEthernet0/12

switchport access vlan 100

speed 100

duplex full

!

interface GigabitEthernet0/13

switchport access vlan 100

speed 100

duplex full

!

interface GigabitEthernet0/14

switchport access vlan 100

speed 100

duplex full

!

interface GigabitEthernet0/15

switchport access vlan 100

speed 100

duplex full

!

interface GigabitEthernet0/16

switchport access vlan 100

speed 100

duplex full

!

interface GigabitEthernet0/17

speed 100

duplex full

!

interface GigabitEthernet0/27

switchport access vlan 400

!

interface GigabitEthernet0/28

switchport access vlan 400

!

interface GigabitEthernet0/29

switchport access vlan 400

!

interface GigabitEthernet0/30

switchport access vlan 200

!

interface GigabitEthernet0/31

switchport access vlan 200

!

interface GigabitEthernet0/45

switchport access vlan 500

speed 100

duplex full

!

interface GigabitEthernet0/46

switchport access vlan 500

speed 100

duplex full

!

interface GigabitEthernet0/47

switchport trunk encapsulation dot1q

switchport trunk native vlan 999

switchport trunk allowed vlan 100,200,300,400,600,700

switchport mode trunk

channel-group 1 mode on

!

interface GigabitEthernet0/48

switchport trunk encapsulation dot1q

switchport trunk native vlan 999

switchport trunk allowed vlan 100,200,300,400,600,700

switchport mode trunk

channel-group 1 mode on

!

interface Vlan1

no ip address

shutdown

!

interface Vlan100

ip address 192.168.40.11 255.255.252.0

no ip redirects

no ip proxy-arp

standby 1 ip 192.168.40.1

standby 1 priority 110

standby 1 preempt

standby 1 track Vlan600 20

!

interface Vlan200

no ip address

!

interface Vlan600

ip address 192.168.35.1 255.255.255.0

!

router ospf 7

log-adjacency-changes

network 192.168.0.0 0.0.255.255 area 0

!

ip classless

=====================

When I shutdown interface gig 0/2, interface gig0/3 and gig0/4 will go down as well and come back online after a while.

Thanks for your help.

amit-singh · ‎06-30-2005

Please provide us with a n/w topology diagram. Its not clear that which neighbor is going down, is it the other 3560 or some other. lets us know that which ports are you shutting down and neighbor is connected to which ports. which router you are talking about.

Please explain it more.

-amit singh

rseiler · ‎07-06-2005

Your question is really missing a BUNCH of details, but I will take a stab at it:

1) Why on earth do you have a keepalive set to 1800 seconds on the router?

2) Your discussion and config above only talks about qty 2 c3560 switches. Where is the router in this topology?

3) You are going against several Cisco best practices here with your trunk ports:

a) I would never config a port-channel as mode 'on' because the switches will ignore any errors on the ports that would not keep the channel stable because you have configured them to hard set on. ALWAYS set the port channel to mode 'desirable silent'. The config needs to match on both ends of the link.

b) I would never config a port as a trunk mode 'on' without also running UDLD. It appears that your 2-port port-channel trunk above is using copper ports. You MUST enable UDLD on the copper gigabit ports manually (UDLD is enable by default on fiber gigabit ports). You may need to 'udld enable' globally on the switch depending on the IOS version. Obviously, as above, the same config needs to be done on both switches.

4) The log message that you get when you say ports g0/3 and g0/4 go down, is that for just VLAN 100 or are they line-protocol messages?

5) When port g0/2 goes down, are there any other ports in VLAN 100 still up?

6) What are the results of the following commands:

show int g0/3 switchport

show spanning-tree summary

show spanning-tree int po1

show spanning-tree int g0/2

show spanning-tree int g0/3

show spanning-tree int g0/4

show spanning-tree vlan 100

show spanning-tree vlan 600

show int status

show etherchannel summary

show etherchannel detail

show int trunk mod 0

Post more details and I'll try to help...

bluejays · ‎07-08-2005

sorry that I didn't put the detail info. The topology is like this.

3560===============3560

1 1 1 1 1 1

1 1 1----R1---------1 1 1

1 1 1 1

1 1-------R2----------1 1

1---------R3------------1

Left hand is VLAN 600, right hand is VLAN 700

when you shutdown the switch port in VLAN 600, any of them, the other 2 ports in VLAN 600 will flap. Same result applies to VLAN 700

Thanks for your advise. I had remove the keepalive 1800 on all the routers, so the interface remains up/up issue is gone.

Any input is appreciated. I will have more detail output tomorrow.

Thanks

Nick

rseiler · ‎07-08-2005

Your text diagram didn't keep the spacing properly, please include it as an attachment. Thanks.