Essay
Differences between STP Protocols
Author: Dan Wangberg
Term: HT13
Course: 1DV447 Advanced LAN
Technologies
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Table of Contents
Table of Contents ............................................................................................. 2
1.
Problem Definition................................................................................... 3
2. Topology ...................................................................................................... 4
3. Configuration ............................................................................................... 5
3.1 About the Configuration ...................................................................... 14
4. Tests............................................................................................................ 15
5. Reflections ................................................................................................. 17
6. References .................................................................................................. 18
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1. Problem Definition
As we all know there are numerous types of STP and they all intend to fill some
form of special purpose. There is also lots of information regarding the different
protocols[1], but not when to actually use them.
Thus when to actually use what protocol is to me yet unknown. When is MSTP
better than RSTP, how many Vlans are suitable to have when using the different
protocols and how fast respectively slow are they with different number of vlans.
I intend to further look in to these protocols and test them to try and figure out when
it is appropriate to use what type of STP.
For example lets say there are three switches connected to eachother in a triangle
formation. Each of the switches contains 10 vlans. What would be most suitable to
use, MSTP, RSTP, PVST?
There are numerous occasions and different scenarios to test, but I am hoping that I
can conclude a baseline of where the different protocols are ”best”.
Another example with the same topology could be if we now have two or more links
between the switches, since this might make MSTP a more attractive protocol than
STP. The number of Vlans could also be changed.
To do this I intend to compare them with eachother. Setting up different scenarios
and testing them using the different protocols. Measure the speed I get when
netperfing the different Vlans, aswell as checking how long the downtime will be for
failure.
In order to do this three connected switches in a triangle will be required. The tests
that will be conducted are as follows;




Check the throughput of the links when using different protocols
Check what happens when adding Vlans when the switchs is
operational
Forcing STP to recalculate its path and see how long it takes.
Investigate how long it takes for ”cold” switches to start up and
calculate their paths using different protocols
Besides these practical test a theoretical analysis will be done regarding the
different protocols, to see if the literature and other sources have any
adequate explanations on the matter in question. These sources will lean
heavily on the Cisco course material and configuration guides.
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2. Topology
The following is the topology used for conducting all the practical tests. Note that
R3 is used as router on a stick for the switches while R2 and R1 is being used by
other members of the group.
4 (18)
3. Configuration
The following is the show running-configuration output from the different units that
affect my part of the topology.
R3
Building configuration...
Current configuration : 1126 bytes
!
version 12.4
service timestamps debug datetime msec
service timestamps log datetime msec
no service password-encryption
!
hostname R3
!
boot-start-marker
boot-end-marker
!
!
no aaa new-model
memory-size iomem 10
!
!
ip cef
!
!
!
!
voice-card 0
no dspfarm
!
!
!
!
!
!
!
!
!
!
!
!
!
!
!
!
!
!
!
!
interface FastEthernet0/0
no ip address
shutdown
duplex auto
speed auto
!
interface FastEthernet0/1
no ip address
5 (18)
S2
duplex auto
speed auto
!
interface FastEthernet0/1.10
encapsulation dot1Q 10
ip address 10.10.10.2 255.255.255.128
!
interface FastEthernet0/1.20
encapsulation dot1Q 20
ip address 10.10.10.130 255.255.255.128
!
interface FastEthernet0/1.50
encapsulation dot1Q 50
ip address 11.0.0.1 255.255.255.128
!
interface FastEthernet0/1.51
encapsulation dot1Q 51
ip address 11.0.0.129 255.255.255.128
!
interface Serial0/0/0
no ip address
shutdown
clock rate 125000
!
interface Serial0/0/1
no ip address
shutdown
clock rate 125000
!
!
!
ip http server
no ip http secure-server
!
!
!
!
!
control-plane
!
!
!
!
!
!
!
!
!
!
line con 0
line aux 0
line vty 0 4
login
!
scheduler allocate 20000 1000
!
end
Show runn
Building configuration...
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Current configuration : 3422 bytes
!
version 12.2
no service pad
service timestamps debug datetime msec
service timestamps log datetime msec
no service password-encryption
!
hostname S2
!
boot-start-marker
boot-end-marker
!
!
no aaa new-model
system mtu routing 1500
ip subnet-zero
ip routing
!
!
!
!
--More-crypto pki trustpoint TP-self-signed-4185319936
enrollment selfsigned
subject-name cn=IOS-Self-Signed-Certificate-4185319936
revocation-check none
rsakeypair TP-self-signed-4185319936
!
!
crypto pki certificate chain TP-self-signed-4185319936
certificate self-signed 01
3082023B 308201A4 A0030201 02020101 300D0609 2A864886 F70D0101 04050030
31312F30 2D060355 04031326 494F532D 53656C66 2D536967 6E65642D 43657274
69666963 6174652D 34313835 33313939 3336301E 170D3933 30333031 30303030
35315A17 0D323030 31303130 30303030 305A3031 312F302D 06035504 03132649
4F532D53 656C662D 5369676E 65642D43 65727469 66696361 74652D34 31383533
31393933 3630819F 300D0609 2A864886 F70D0101 01050003 818D0030 81890281
810096B9 74AA0B44 90719192 73E137FC BF3DA694 AE2BAA91 9277277A BF716F22
3B83DA0C D2452DBF 6EF55F74 5B8AD6FB 98338C2B 5EEBB8D4 0E3FC235
BA579C2D
4AAC24BB 5C4922F9 31F0009D A4B1D64A 1F8AE764 E794A0AF A4CBE680
DE71FD18
DBE1D45F 910E0EB6 ECEDF128 8D7510ED B796E813 235A6F43 9681A11E 8700A425
EBE30203 010001A3 63306130 0F060355 1D130101 FF040530 030101FF 300E0603
551D1104 07300582 0353322E 301F0603 551D2304 18301680 14ADF22D 3752119D
FA5329BC DF30E1C8 4D0FEE66 38301D06 03551D0E 04160414 ADF22D37 52119DFA
5329BCDF 30E1C84D 0FEE6638 300D0609 2A864886 F70D0101 04050003 81810042
--More-54CCB7C2 0B43AADD 0FF67A60 1C065E27 BA32FA32 D0325C9A
C99A5C16 F74CC2E9
2DE103D0 85592EEC BA6C5D04 228BFFBC 722A5495 205BE050 CD695DA6
7BA7CBC2
2CA06A72 67217A03 4F0AD94D E41C54D1 C5A50A76 5BFDCC01 B4681B29
99A2A745
F4ACFB2B E12DC9A9 5207CE6B 0B770B45 99EA698D 76578260 86435B62 39AFE1
quit
!
!
!
7 (18)
!
!
!
spanning-tree mode pvst
spanning-tree extend system-id
no spanning-tree vlan 225-1001
!
vlan internal allocation policy ascending
!
!
!
!
interface FastEthernet0/1
!
interface FastEthernet0/2
--More-switchport access vlan 10
switchport mode access
!
interface FastEthernet0/3
no switchport
ip address 11.0.2.1 255.255.255.128
!
interface FastEthernet0/4
no switchport
ip address 11.0.2.129 255.255.255.128
!
interface FastEthernet0/5
!
interface FastEthernet0/6
!
interface FastEthernet0/7
!
interface FastEthernet0/8
!
interface FastEthernet0/9
!
interface FastEthernet0/10
!
--More-interface FastEthernet0/11
switchport access vlan 10
switchport mode access
!
interface FastEthernet0/12
!
interface FastEthernet0/13
!
interface FastEthernet0/14
!
interface FastEthernet0/15
!
interface FastEthernet0/16
!
interface FastEthernet0/17
!
interface FastEthernet0/18
!
interface FastEthernet0/19
switchport trunk encapsulation dot1q
switchport mode trunk
8 (18)
!
interface FastEthernet0/20
--More-switchport trunk encapsulation dot1q
switchport mode trunk
!
interface FastEthernet0/21
switchport trunk encapsulation dot1q
switchport mode trunk
shutdown
!
interface FastEthernet0/22
switchport trunk encapsulation dot1q
switchport mode trunk
!
interface FastEthernet0/23
!
interface FastEthernet0/24
!
interface GigabitEthernet0/1
!
interface GigabitEthernet0/2
!
interface Vlan1
no ip address
!
--More-ip classless
ip http server
ip http secure-server
!
!
!
control-plane
!
!
line con 0
line vty 0 4
login
line vty 5 15
login
!
end
S4
S2#
Show runn
Building configuration...
Current configuration : 3412 bytes
!
version 12.2
no service pad
service timestamps debug datetime msec
service timestamps log datetime msec
no service password-encryption
!
hostname S4
!
boot-start-marker
boot-end-marker
!
9 (18)
!
no aaa new-model
system mtu routing 1500
ip subnet-zero
!
!
!
!
crypto pki trustpoint TP-self-signed-3180427776
--More-enrollment selfsigned
subject-name cn=IOS-Self-Signed-Certificate-3180427776
revocation-check none
rsakeypair TP-self-signed-3180427776
!
!
crypto pki certificate chain TP-self-signed-3180427776
certificate self-signed 01
3082023B 308201A4 A0030201 02020101 300D0609 2A864886 F70D0101 04050030
31312F30 2D060355 04031326 494F532D 53656C66 2D536967 6E65642D 43657274
69666963 6174652D 33313830 34323737 3736301E 170D3933 30333031 30303030
35305A17 0D323030 31303130 30303030 305A3031 312F302D 06035504 03132649
4F532D53 656C662D 5369676E 65642D43 65727469 66696361 74652D33 31383034
32373737 3630819F 300D0609 2A864886 F70D0101 01050003 818D0030 81890281
8100EA53 45297063 8ECA3561 931FE18E 48C524D0 DB5277F6 9C89063D 872F134F
3592E067 7CE47A5B 3E270363 2DADEED9 837DDFF9 C92594D2 E8254DCC
94A29C31
3B56C9CF C5E2C472 0C556B80 BEEDA6FC 5779877C 60FADA37 8A776A60
AC539A62
8F58C5B3 7DC66A62 4F31EDDF 432FF044 11CEC9CF 25145523 66F90A7B B01E470C
25F70203 010001A3 63306130 0F060355 1D130101 FF040530 030101FF 300E0603
551D1104 07300582 0353342E 301F0603 551D2304 18301680 14D74982 46CCD45D
111D74AC 1FA58DE3 B7541DEB B6301D06 03551D0E 04160414 D7498246 CCD45D11
1D74AC1F A58DE3B7 541DEBB6 300D0609 2A864886 F70D0101 04050003 81810037
2E857C22 A0C49234 DFBCBFEB 656B239E 6AC8D88B BEBBE50F 2200BF82
FA3103CA
--More-0D7A045D B3271FF7 C74B8702 3642C23C AE0480DA 96990D8E
1DA037EE D0A8112D
4169FD06 5D1795E5 AD019991 3737FF5F 19397715 865C550F B0B7C110 7E91C629
50FC8230 8CA8BC45 7955792D 16ED8CD7 4C8572BC 4E5A41FB 875E7BA2 809F0E
quit
!
!
!
!
!
spanning-tree mode pvst
spanning-tree extend system-id
!
vlan internal allocation policy ascending
!
!
!
interface FastEthernet0/1
switchport mode trunk
!
interface FastEthernet0/2
switchport access vlan 53
switchport mode access
!
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--More-interface FastEthernet0/3
switchport access vlan 52
switchport mode access
!
interface FastEthernet0/4
!
interface FastEthernet0/5
switchport access vlan 50
switchport mode access
!
interface FastEthernet0/6
switchport access vlan 51
switchport mode access
!
interface FastEthernet0/7
switchport access vlan 52
switchport mode access
!
interface FastEthernet0/8
switchport access vlan 53
switchport mode access
!
interface FastEthernet0/9
--More-!
interface FastEthernet0/10
!
interface FastEthernet0/11
switchport mode access
!
interface FastEthernet0/12
switchport access vlan 10
switchport mode access
!
interface FastEthernet0/13
!
interface FastEthernet0/14
!
interface FastEthernet0/15
!
interface FastEthernet0/16
!
interface FastEthernet0/17
!
interface FastEthernet0/18
!
interface FastEthernet0/19
--More-switchport mode trunk
!
interface FastEthernet0/20
switchport mode trunk
!
interface FastEthernet0/21
!
interface FastEthernet0/22
!
interface FastEthernet0/23
switchport mode trunk
!
interface FastEthernet0/24
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switchport mode trunk
!
interface GigabitEthernet0/1
!
interface GigabitEthernet0/2
!
interface Vlan1
no ip address
no ip route-cache
!
--More-ip http server
ip http secure-server
!
control-plane
!
!
line con 0
line vty 0 4
login
line vty 5 15
login
!
end
S5
S4#
Show runn
Building configuration...
Current configuration : 1435 bytes
!
version 12.1
no service pad
service timestamps debug uptime
service timestamps log uptime
no service password-encryption
!
hostname S5
!
!
ip subnet-zero
!
ip ssh time-out 120
ip ssh authentication-retries 3
!
!
spanning-tree mode pvst
no spanning-tree optimize bpdu transmission
spanning-tree extend system-id
no spanning-tree vlan 159-200,211-300
!
--More-!
!
!
interface FastEthernet0/1
!
interface FastEthernet0/2
switchport access vlan 20
switchport mode access
!
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interface FastEthernet0/3
switchport access vlan 54
!
interface FastEthernet0/4
switchport access vlan 55
!
interface FastEthernet0/5
!
interface FastEthernet0/6
!
interface FastEthernet0/7
!
interface FastEthernet0/8
!
--More-interface FastEthernet0/9
!
interface FastEthernet0/10
!
interface FastEthernet0/11
!
interface FastEthernet0/12
!
interface FastEthernet0/13
!
interface FastEthernet0/14
!
interface FastEthernet0/15
!
interface FastEthernet0/16
!
interface FastEthernet0/17
!
interface FastEthernet0/18
!
interface FastEthernet0/19
!
interface FastEthernet0/20
--More-!
interface FastEthernet0/21
switchport mode trunk
!
interface FastEthernet0/22
switchport mode trunk
!
interface FastEthernet0/23
switchport mode trunk
!
interface FastEthernet0/24
switchport mode trunk
!
interface GigabitEthernet0/1
!
interface GigabitEthernet0/2
!
interface Vlan1
no ip address
no ip route-cache
!
ip http server
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!
--More-line con 0
line vty 0 4
login
line vty 5 15
login
!
!
end
S5#
3.1 About the Configuration
Note that some of the configuration are used by other members of the group. Also
note that during the tests the configuration is changed, however this is not attached
in the essay, only explained during the tests. An example of this is the changing of
STP mode or the adding and removing of VLANs.
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4. Tests
The first test conducted was to check the throughput of the network when using
different STP modes. Granted, the packets are quite small and are quite similar, but I
did belive that some differences would present themselfs due to various hello-timers
and other things.
The test was done by using netperf, a tool to check how much throughput you can
get from one netperfinstance to another[2]. The test was done five times using the
different protocols MSTP, Rapid PVST and PVST. This resulted in the following
throughputs;
PVST
91.67
91.68
91.66
91.67
91.64
STP
Not supported
Not supported
Not supported
Not supported
Not supported
MSTP
91.66
91.66
91.68
91.66
91.67
PVST+
91.66
91.67
91.67
91.67
91.65
(Note that I had intended to test STP aswell but it was not supported on the
switches.)
The second test was to see what would happen if one were to add several vlans when
having an active ping to see if the switch would drop any packages. My hypothosis
here were that the cpu of the switch might be strained enough to make the network
less reliable.
By adding 120 vlans to the switchs while the ping was active, the cpu only reached
about 30% workload. Adding more vlans was not possible as the maximum number
of STP instances the switch in question could have was 128.
The third test was done to see how long it would take the different protocols to
recalculate their paths when the root port went down. This was done by setting up a
ping between two vlans and then shutting down interface fa 0/21 which in this case
was rootport and checking how many pings would be lost. The images on the next
page shows the testresults.
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MSTP
PVST
RPVST
As one can see from the tests 31 pings were lost druing the tests, regardless of
protocol.
The last test done was starting up the switches using the different protocols to
determine which would be up and running the fastest. The time it took for the
switches to boot up and sucesfully transmit a ping using the different STP were as
follows;
STP
Not supported
PVST
1.55 sec
PVST+
1.53
MSTP
1.53
This shows that the PVST+ and MSTP were a bit faster than normal PVST.
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5. Reflections
All of the tests done and all of the resarch I did indicates one thing. It does not
matter at all what protocol you use. Obviously in a large network pvst+ is better than
pvst due to it being a tad faster. But part from this their is actually not much thats
different with these protocols.
When doing the tests I first tried adding about a 1000 vlans to check the cpu
workload on the switches. This was while having VTP on. This resulted in the
switches complaing that they had exceeded the maxmimum number of vlans
allowed. By looking up the different switches configurationguide I noticed that the
Catalyst 2950 only supports 64[3] STP instances and the 3560 only supports 128[4].
This means that even though my tests showed that their were no differences in what
you use, depending on the types of switches you are using it actually does matter. In
a network with more than 64 vlans with 2950 switches using pvst would not work.
MSTP would have to be used to circumvent this. In other words as soon as you have
more vlans than the amount of stp instances your switches can handle MSTP is the
better choice.
However in a network were 20 vlans are presant and 3560 switches are used it
would not actually matter if you used pvst or MSTP. I personally find mstp a bit
easier to configure and decide where the traffic should traverse the network, but this
is perfectly doable in PVST aswell, hence it is not something that negativly impacts
the PVST protocol.
The tests I performed could have been done using wireshark and checking the
individual packets for a more extensive result than what my tests showed. However I
was not intrested in exactly how many bytes of overhead the different protocols
would produce. I wanted to know if there were any real reasons why one protocol
would be better t use than another.
My tests did not show many differences at all in the protocols. I find this as
intressting as if they had shown lots of differences. Now it is clear that they are
actually extremly similar and the only real thing that has to be taken into account
when deciding what to use is weather or not you will have more vlans than your
switches amount of viable stp instances.
I do not belive that the other groupmembers impacted my tests in any way. When
one person were conducting their tests the other members would have to wait, as the
tests would be tainted otherwise.
The topology did suffice for the tests I performed, but could have been made more
extensive with more switches and more paths throughout the network.
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6. References
[1] D. Huckaby, CCNP Switch 642813: Official
Certification Guide, Indianapolis: Cisco Press, 2011.
[2] Netperf.com. 2014-01-09. [Online]. Available: http://www.netperf.org/netperf/
[3] Cisco.com. 2014-01-08. [Online]. Available:
http://www.cisco.com/en/US/docs/switches/lan/catalyst2950/software/release
/12.1_6_ea2c/configuration/guide/swgstp.html
[4] Cisco.com. 2014-01-08. [Online]. Available:
http://www.cisco.com/en/US/docs/switches/lan/catalyst3750x_3560x/softwar
e/release/12.2_55_se/configuration/guide/swstp.html
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