L2 etherchannel + inter vlan routing issue

Istvan kelemen · ‎02-03-2013

Hello Guys!

Etherchannel is configured between SW1 and SW2. The ports are g1/1 and g1/2 both are trunkporst of course and member of channel-group 1.

If i unplug any wire the connection will never establis again. (Can't ping to SW2 vlan 100 or 101 from SW1 vlan 100 or 101 however the leds are green)

Without etherchannel, (with R-STP) it just works fine, the connection recovers whitin 0,1 sec.

I've tested it in GSN3 too with C2691's routers. (one as router 2 as switch using NM-SW16's)

Sorry about not having a real cisco EQ, i'm learning CCNA.

Reza Sharifi · ‎02-03-2013

Hi,

I don't know how good this will work on GNS, but if you are using reall switches and Etherchannel is configured correctly and you run a continues ping from one a PC in vlan 100 to another PC in vlan 101, and you disconnect one of the links on the Etherchannle, the max ping you should lose is about 3 and the other link should take over and forward traffic.

Can you post the Etherchannel configs from both switches?

HTH

Istvan kelemen · ‎02-03-2013

Here you go!

SW 1

version 12.2

no service timestamps log datetime msec

no service timestamps debug datetime msec

no service password-encryption

!

hostname Switch

!

spanning-tree mode rapid-pvst

!

interface FastEthernet0/1

switchport access vlan 100

switchport mode access

!

interface FastEthernet0/2

switchport access vlan 100

switchport mode access

!

interface FastEthernet0/3

switchport access vlan 101

switchport mode access

!

interface FastEthernet0/4

switchport access vlan 101

switchport mode access

!

interface FastEthernet0/24

switchport mode trunk

!

interface GigabitEthernet1/1

channel-group 1 mode on

switchport mode trunk

spanning-tree portfast

!

interface GigabitEthernet1/2

channel-group 1 mode on

switchport mode trunk

spanning-tree portfast

!

interface Port-channel 1

switchport mode trunk

SW2

version 12.2

no service timestamps log datetime msec

no service timestamps debug datetime msec

no service password-encryption

!

hostname Switch

!

spanning-tree mode rapid-pvst

!

interface FastEthernet0/1

switchport access vlan 100

!

interface FastEthernet0/2

switchport access vlan 101

!

interface GigabitEthernet1/1

channel-group 1 mode on

spanning-tree portfast

!

interface GigabitEthernet1/2

channel-group 1 mode on

spanning-tree portfast

!

interface Port-channel 1

SW 1

Switch#sh interfaces etherchannel

GigabitEthernet1/1:

Port state = 1

Channel group = 1 Mode = On Gcchange = -

Port-channel = Po1 GC = - Pseudo port-channel = Po1

Port index = 0 Load = 0x0 Protocol = -

Age of the port in the current state: 00d:00h:01m:45s

GigabitEthernet1/2:

Port state = 1

Channel group = 1 Mode = On Gcchange = -

Port-channel = Po1 GC = - Pseudo port-channel = Po1

Port index = 0 Load = 0x0 Protocol = -

Age of the port in the current state: 00d:00h:01m:45s

----

Port-channel1:Port-channel1

Age of the Port-channel = 00d:00h:02m:18s

Logical slot/port = 2/1 Number of ports = 2

GC = 0x00000000 HotStandBy port = null

Port state =

Protocol = 3

Port Security = Disabled

Ports in the Port-channel:

Index Load Port EC state No of bits

------+------+------+------------------+-----------

0 00 Gig1/1 On 0

0 00 Gig1/2 On 0

Time since last port bundled: 00d:00h:01m:45s Gig1/2

SW 2

GigabitEthernet1/1:

Port state = 1

Channel group = 1 Mode = On Gcchange = -

Port-channel = Po1 GC = - Pseudo port-channel = Po1

Port index = 0 Load = 0x0 Protocol = -

Age of the port in the current state: 00d:00h:02m:00s

GigabitEthernet1/2:

Port state = 1

Channel group = 1 Mode = On Gcchange = -

Port-channel = Po1 GC = - Pseudo port-channel = Po1

Port index = 0 Load = 0x0 Protocol = -

Age of the port in the current state: 00d:00h:02m:00s

----

Port-channel1:Port-channel1

Age of the Port-channel = 00d:00h:02m:16s

Logical slot/port = 2/1 Number of ports = 2

GC = 0x00000000 HotStandBy port = null

Port state =

Protocol = 3

Port Security = Disabled

Ports in the Port-channel:

Index Load Port EC state No of bits

------+------+------+------------------+-----------

0 00 Gig1/1 On 0

0 00 Gig1/2 On 0

Time since last port bundled: 00d:00h:02m:00s Gig1/2

kcnajaf · ‎02-03-2013

Hi Istvan,

Looks like you dont have consistent etherchannel configuration. Dont enable the portfast on trunk links. Modify the configurations as below.

SW 1

interface GigabitEthernet1/1

speed 1000

duplex full

channel-group 1 mode on

shut

!

interface GigabitEthernet1/2

speed 1000

duplex full

channel-group 1 mode on

shut

!

interface Port-channel 1

switchport mode trunk

switchport trunk encapsulation dot1q

SW2

interface GigabitEthernet1/1

speed 1000

duplex full

channel-group 1 mode on

shut

!

interface GigabitEthernet1/2

speed 1000

duplex full

channel-group 1 mode on

shut

!

interface Port-channel 1

switchport mode trunk

switchport trunk encapsulation dot1q

Once the port channel interface are configured give no shut on the physcial interface and verify if the ehther channels are formed. If yes then try your failover test.

Being said above this may not work as expected on a GNS3/PT environment. The best way to check this when you shutdown the one port of SW1 verify the other end of port (SW2) is showing as down. If not the simulated switch is not cabaple of detecting the physical link failure and keeps on forwarding traffic on that interface. Those are the limitations of a simulated environment.

Hope that helps.

Regards

Najaf

glen.grant · ‎02-03-2013

Try changing the connecting ports to " channel-group 1 mode desirable non-silent" and see if it changes anything.