switching: August 2011

Monday 22 August 2011

STP over etherchannel

I am trying to understand how STP works on etherchannel. I need to read further on the STP over etherchannel. Need to buy the cisco press book today. Going out to have it.

I like this scenario and its easy to understand:

Here is the config of the router:

interface FastEthernet0/0
ip address 192.168.1.1 255.255.255.0
duplex auto
speed auto
!
interface FastEthernet0/0.10
encapsulation dot1Q 10
ip address 192.168.10.1 255.255.255.0
!
interface FastEthernet0/0.20
encapsulation dot1Q 20
ip address 192.168.20.1 255.255.255.0
!

Switch 0:

Switch#show vtp s
Switch#show vtp status
VTP Version : 2
Configuration Revision : 4
Maximum VLANs supported locally : 255
Number of existing VLANs : 7
VTP Operating Mode : Server
VTP Domain Name : SERVER
VTP Pruning Mode : Disabled
VTP V2 Mode : Disabled
VTP Traps Generation : Disabled
MD5 digest : 0x37 0xAC 0x93 0xA6 0xD1 0x18 0x77 0xA3
Configuration last modified by 0.0.0.0 at 3-1-93 00:56:51
Local updater ID is 0.0.0.0 (no valid interface found)

VLAN Name Status Ports
---- -------------------------------- --------- -------------------------------
1 default active Fa0/6, Fa0/7, Fa0/8, Fa0/9
Fa0/10, Fa0/11, Fa0/12, Fa0/13
Fa0/14, Fa0/15, Fa0/16, Fa0/17
Fa0/18, Fa0/19, Fa0/20, Fa0/21
Fa0/22, Fa0/23, Fa0/24, Gig1/1
Gig1/2
10 ten active Fa0/4
20 twenty active Fa0/5
1002 fddi-default act/unsup
1003 token-ring-default act/unsup
1004 fddinet-default act/unsup
1005 trnet-default act/unsup

On other switches you need to configure the same as in switch 0

simulation of layer3 switch on gns3

I am searching if there is a way to simulate l3 switch on gns3. Need some research to be done. It will take some time. I am downloading IOS.

In the mean time I am working on the router on a stick and etherchannel. will keep posting.

Sunday 21 August 2011

VTP and PVST

I configured VTP domain called SERVER with 3 vlans 10,20,30. I also enabled PVST in this scenario.

Here is the config part:

Switch0

hostname Switch0
!
!
spanning-tree vlan 10 priority 24576
!
interface FastEthernet0/1
switchport mode trunk
!
interface FastEthernet0/2
switchport mode trunk
!
interface FastEthernet0/3
switchport access vlan 10
switchport mode access
!
interface FastEthernet0/4
switchport access vlan 20
switchport mode access
!
interface FastEthernet0/5
switchport access vlan 30
switchport mode access

Switch0(config)#do sh vtp status
VTP Version : 2
Configuration Revision : 6
Maximum VLANs supported locally : 255
Number of existing VLANs : 8
VTP Operating Mode : Server
VTP Domain Name : SERVER
VTP Pruning Mode : Disabled
VTP V2 Mode : Disabled
VTP Traps Generation : Disabled
MD5 digest : 0xEA 0x6D 0x8A 0x70 0x59 0xE8 0x24 0x5D
Configuration last modified by 0.0.0.0 at 3-1-93 00:09:36
Local updater ID is 0.0.0.0 (no valid interface found)

Switch0#show spanning-tree
VLAN0001
Spanning tree enabled protocol ieee
Root ID Priority 32769
Address 0001.C716.A7B5
Cost 19
Port 1(FastEthernet0/1)
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec

Bridge ID Priority 32769 (priority 32768 sys-id-ext 1)
Address 0004.9A15.C545
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Aging Time 20

Interface Role Sts Cost Prio.Nbr Type
---------------- ---- --- --------- -------- --------------------------------
Fa0/1 Root FWD 19 128.1 P2p
Fa0/2 Desg FWD 19 128.2 P2p

VLAN0010
Spanning tree enabled protocol ieee
Root ID Priority 24586
Address 0004.9A15.C545
This bridge is the root
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec

Bridge ID Priority 24586 (priority 24576 sys-id-ext 10)
Address 0004.9A15.C545
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Aging Time 20

Interface Role Sts Cost Prio.Nbr Type
---------------- ---- --- --------- -------- --------------------------------
Fa0/3 Desg FWD 19 128.3 P2p
Fa0/1 Desg FWD 19 128.1 P2p
Fa0/2 Desg FWD 19 128.2 P2p

VLAN0020
Spanning tree enabled protocol ieee
Root ID Priority 24596
Address 0001.C716.A7B5
Cost 19
Port 1(FastEthernet0/1)
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec

Bridge ID Priority 32788 (priority 32768 sys-id-ext 20)
Address 0004.9A15.C545
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Aging Time 20

Interface Role Sts Cost Prio.Nbr Type
---------------- ---- --- --------- -------- --------------------------------
Fa0/4 Desg FWD 19 128.4 P2p
Fa0/1 Root FWD 19 128.1 P2p
Fa0/2 Desg FWD 19 128.2 P2p

VLAN0030
Spanning tree enabled protocol ieee
Root ID Priority 24606
Address 0030.A316.06BD
Cost 19
Port 1(FastEthernet0/1)
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec

Bridge ID Priority 32798 (priority 32768 sys-id-ext 30)
Address 0004.9A15.C545
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Aging Time 20

Interface Role Sts Cost Prio.Nbr Type
---------------- ---- --- --------- -------- --------------------------------
Fa0/1 Root FWD 19 128.1 P2p
Fa0/2 Altn BLK 19 128.2 P2p

Switch0#show spanning-tree summary
Switch is in pvst mode
Root bridge for: 10
Extended system ID is enabled
Portfast Default is disabled
PortFast BPDU Guard Default is disabled
Portfast BPDU Filter Default is disabled
Loopguard Default is disabled
EtherChannel misconfig guard is disabled
UplinkFast is disabled
BackboneFast is disabled
Configured Pathcost method used is short

Name Blocking Listening Learning Forwarding STP Active
---------------------- -------- --------- -------- ---------- ----------
VLAN0001 0 0 0 2 2
VLAN0010 0 0 0 3 3
VLAN0020 0 0 0 3 3
VLAN0030 1 0 0 1 2

---------------------- -------- --------- -------- ---------- ----------
4 vlans 1 0 0 9 10

switch1

Switch1#show spanning-tree
VLAN0001
Spanning tree enabled protocol ieee
Root ID Priority 32769
Address 0001.C716.A7B5
This bridge is the root
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec

Bridge ID Priority 32769 (priority 32768 sys-id-ext 1)
Address 0001.C716.A7B5
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Aging Time 20

Interface Role Sts Cost Prio.Nbr Type
---------------- ---- --- --------- -------- --------------------------------
Fa0/2 Desg FWD 19 128.2 P2p
Fa0/1 Desg FWD 19 128.1 P2p

VLAN0010
Spanning tree enabled protocol ieee
Root ID Priority 24586
Address 0004.9A15.C545
Cost 19
Port 1(FastEthernet0/1)
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec

Bridge ID Priority 32778 (priority 32768 sys-id-ext 10)
Address 0001.C716.A7B5
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Aging Time 20

Interface Role Sts Cost Prio.Nbr Type
---------------- ---- --- --------- -------- --------------------------------
Fa0/2 Desg FWD 19 128.2 P2p
Fa0/1 Root FWD 19 128.1 P2p
Fa0/3 Desg FWD 19 128.3 P2p

VLAN0020
Spanning tree enabled protocol ieee
Root ID Priority 24596
Address 0001.C716.A7B5
This bridge is the root
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec

Bridge ID Priority 24596 (priority 24576 sys-id-ext 20)
Address 0001.C716.A7B5
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Aging Time 20

Interface Role Sts Cost Prio.Nbr Type
---------------- ---- --- --------- -------- --------------------------------
Fa0/2 Desg FWD 19 128.2 P2p
Fa0/1 Desg FWD 19 128.1 P2p
Fa0/4 Desg FWD 19 128.4 P2p

VLAN0030
Spanning tree enabled protocol ieee
Root ID Priority 24606
Address 0030.A316.06BD
Cost 19
Port 2(FastEthernet0/2)
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec

Bridge ID Priority 32798 (priority 32768 sys-id-ext 30)
Address 0001.C716.A7B5
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Aging Time 20

Interface Role Sts Cost Prio.Nbr Type
---------------- ---- --- --------- -------- --------------------------------
Fa0/5 Desg FWD 19 128.5 P2p
Fa0/2 Root FWD 19 128.2 P2p
Fa0/1 Desg FWD 19 128.1 P2p

Switch 2

Switch2#sh spanning-tree
VLAN0001
Spanning tree enabled protocol ieee
Root ID Priority 32769
Address 0001.C716.A7B5
Cost 19
Port 2(FastEthernet0/2)
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec

Bridge ID Priority 32769 (priority 32768 sys-id-ext 1)
Address 00D0.BA7B.4CA4
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Aging Time 20

Interface Role Sts Cost Prio.Nbr Type
---------------- ---- --- --------- -------- --------------------------------
Fa0/2 Root FWD 19 128.2 P2p
Fa0/1 Altn BLK 19 128.1 P2p

VLAN0010
Spanning tree enabled protocol ieee
Root ID Priority 24586
Address 0004.9A15.C545
Cost 19
Port 2(FastEthernet0/2)
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec

Bridge ID Priority 32778 (priority 32768 sys-id-ext 10)
Address 00D0.BA7B.4CA4
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Aging Time 20

Interface Role Sts Cost Prio.Nbr Type
---------------- ---- --- --------- -------- --------------------------------
Fa0/2 Root FWD 19 128.2 P2p
Fa0/3 Desg FWD 19 128.3 P2p
Fa0/1 Desg FWD 19 128.1 P2p

VLAN0020
Spanning tree enabled protocol ieee
Root ID Priority 24596
Address 0001.C716.A7B5
Cost 19
Port 2(FastEthernet0/2)
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec

Bridge ID Priority 32788 (priority 32768 sys-id-ext 20)
Address 00D0.BA7B.4CA4
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Aging Time 20

Interface Role Sts Cost Prio.Nbr Type
---------------- ---- --- --------- -------- --------------------------------
Fa0/2 Root FWD 19 128.2 P2p
Fa0/1 Altn BLK 19 128.1 P2p
Fa0/4 Desg FWD 19 128.4 P2p

VLAN0030
Spanning tree enabled protocol ieee
Root ID Priority 24606
Address 0030.A316.06BD
Cost 19
Port 1(FastEthernet0/1)
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec

Bridge ID Priority 32798 (priority 32768 sys-id-ext 30)
Address 00D0.BA7B.4CA4
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Aging Time 20

Interface Role Sts Cost Prio.Nbr Type
---------------- ---- --- --------- -------- --------------------------------
Fa0/2 Desg FWD 19 128.2 P2p
Fa0/1 Root FWD 19 128.1 P2p
Fa0/5 Desg FWD 19 128.5 P2p

Switch3

Switch3(config)#do sh span
VLAN0001
Spanning tree enabled protocol ieee
Root ID Priority 32769
Address 0001.C716.A7B5
Cost 19
Port 1(FastEthernet0/1)
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec

Bridge ID Priority 32769 (priority 32768 sys-id-ext 1)
Address 0030.A316.06BD
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Aging Time 20

Interface Role Sts Cost Prio.Nbr Type
---------------- ---- --- --------- -------- --------------------------------
Fa0/1 Root FWD 19 128.1 P2p
Fa0/2 Desg FWD 19 128.2 P2p

VLAN0010
Spanning tree enabled protocol ieee
Root ID Priority 24586
Address 0004.9A15.C545
Cost 19
Port 1(FastEthernet0/1)
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec

Bridge ID Priority 32778 (priority 32768 sys-id-ext 10)
Address 0030.A316.06BD
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Aging Time 20

Interface Role Sts Cost Prio.Nbr Type
---------------- ---- --- --------- -------- --------------------------------
Fa0/3 Desg FWD 19 128.3 P2p
Fa0/1 Root FWD 19 128.1 P2p
Fa0/2 Altn BLK 19 128.2 P2p

VLAN0020
Spanning tree enabled protocol ieee
Root ID Priority 24596
Address 0001.C716.A7B5
Cost 19
Port 1(FastEthernet0/1)
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec

Bridge ID Priority 32788 (priority 32768 sys-id-ext 20)
Address 0030.A316.06BD
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Aging Time 20

Interface Role Sts Cost Prio.Nbr Type
---------------- ---- --- --------- -------- --------------------------------
Fa0/4 Desg FWD 19 128.4 P2p
Fa0/1 Root FWD 19 128.1 P2p
Fa0/2 Desg FWD 19 128.2 P2p

VLAN0030
Spanning tree enabled protocol ieee
Root ID Priority 24606
Address 0030.A316.06BD
This bridge is the root
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec

Bridge ID Priority 24606 (priority 24576 sys-id-ext 30)
Address 0030.A316.06BD
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Aging Time 20

Interface Role Sts Cost Prio.Nbr Type
---------------- ---- --- --------- -------- --------------------------------
Fa0/5 Desg FWD 19 128.5 P2p
Fa0/1 Desg FWD 19 128.1 P2p
Fa0/2 Desg FWD 19 128.2 P2p

Spanning tree protocol example with priority change

Here I have changed the default priority of switch0 to 4096 making it root. Wanted to check the port status now. Check the difference. The priority has been changed with below command:

Switch0#conf t
Enter configuration commands, one per line. End with CNTL/Z.
Switch0(config)#spanning-tree vlan 1 priority 4096

Here is one more example STP with defaults

Here I have tried to get the details in the diagram itself. R is root port. D is designated port: Below are the some of the details of some of the switches. Check the role of the switch ports:

Switch1#show spanning-tree
VLAN0001
Spanning tree enabled protocol ieee
Root ID Priority 32769
Address 0000.0C28.2A51
Cost 19
Port 1(FastEthernet0/1)
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec

Bridge ID Priority 32769 (priority 32768 sys-id-ext 1)
Address 0050.0FC0.5B7E
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Aging Time 20

Interface Role Sts Cost Prio.Nbr Type
---------------- ---- --- --------- -------- --------------------------------
Fa0/2 Altn BLK 19 128.2 P2p
Fa0/1 Root FWD 19 128.1 P2p

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Switch2#show spanning-tree
VLAN0001
Spanning tree enabled protocol ieee
Root ID Priority 32769
Address 0000.0C28.2A51
Cost 19
Port 3(FastEthernet0/3)
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec

Bridge ID Priority 32769 (priority 32768 sys-id-ext 1)
Address 0040.0B39.73A1
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Aging Time 20

Interface Role Sts Cost Prio.Nbr Type
---------------- ---- --- --------- -------- --------------------------------
Fa0/2 Desg FWD 19 128.2 P2p
Fa0/1 Desg FWD 19 128.1 P2p
Fa0/3 Root FWD 19 128.3 P2p
Fa0/4 Altn BLK 19 128.4 P2p

How Spanning tree works with diagram

This example will solve most of the issues in understanding STP:

Lets consider how to get to the designated, root and blocked ports. I will try explaining for each switch one by one. Here all switches are having default ID. If ID were different then it would have automatically choose the lowest bridge ID. But here we will try to get with defaults:

Step 1: finding root switch

After analyzing MAC address of all the switch, we found that MAC of Switch 4 is very low and hence its the Root bridge. Lets check the output of this switch

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

Switch#show spanning-tree
VLAN0001
Spanning tree enabled protocol ieee
Root ID Priority 32769
Address 0001.43AD.CAD2
This bridge is the root
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec

Bridge ID Priority 32769 (priority 32768 sys-id-ext 1)
Address 0001.43AD.CAD2
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Aging Time 20

Interface Role Sts Cost Prio.Nbr Type
---------------- ---- --- --------- -------- --------------------------------
Fa0/1 Desg FWD 19 128.1 P2p
Fa0/2 Desg FWD 19 128.2 P2p
Fa0/3 Desg FWD 19 128.3 P2p
Fa0/4 Desg FWD 19 128.4 P2p
================================================

All the ports are designated ports.

Step 2: Finding root ports for each switch

Switch 3: The port connecting directly to switch 4 is the root port
Switch 5: The port directly connected to the switch 4 is the root port
Switch 2:  The port directly connected to the switch 4 is the root port
Switch 1:  The port directly connected to the switch 4 is the root port
Switch 0: There are two paths for the Switch 0 to reach root switch
a> via switch 2 whose path cost is 19+19
b> via switch 1 to Switch 4 directly whose path cost is 19+19
so there is Tie here. Hence lets check the MAC here
Mac of switch 1< Mac of Switch 2
Hence it will choose Switch 1 to reach the root bridge

Step 3: Finding Blocked

Now you need to compare the MAC address of each switch, which ever will be low it will be as Designated port and the one with higher MAC it will be blocked. These blocked ports are Amber in the above diagram.
example switch 1 and Switch 3. THe mac of switch 1 is greater than switch 3, so the port of switch 1 connecting to the switch 3 is Amber.

Important    Lets consider the switch 0 now which is connected to switch 2. The MAC of switch 2 is higher but still it is green. The reason is the cost of the switch 2 to reach root is less than the cost of the switch 0 to reach root. Hence Switch 0 port is Amber.

Hope this helps!!!

till now

I have completed my CCNA and CCNP 642-902.

Now I am going to start my CCNP Switching. I try posting everyday about whatever I read. New network diagrams I wil create in my lab.

Will try to post most most of the content myself.

switching

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