RE: mst - pvst interoperability - will not do load

From: rjonathan@hotpop.com
Date: Thu Oct 17 2002 - 21:41:55 GMT-3

Next message: Brian McGahan: "RE: bgp bestpath med missing-as-worst :-("
Previous message: elping: "Re: CCIE # 10474"
Messages sorted by: [ date ] [ thread ] [ subject ] [ author ] [ attachment ]

Hi Kumar,

I quote this from CCO
http://www.cisco.com/warp/public/473/147.html#recommended_configuration

"Invalid Configuration
While providing easy and seamless interoperability between MST and PVST+,
the PVST+ emulation mechanism implies that any configuration other than the
two previously mentioned ones is invalid. The following are the basic rules
that must be followed to get a successful MST/PVST+ interaction:

If the MST bridge is the root, it must be the root for all VLANs.

If the PVST+ bridge is the root, it must be the root for all VLANs
(including the CST, which always runs on VLAN 1, regardless of the native
VLAN, when running PVST+).

The simulation will fail and produce an error message if the MST bridge is
the root for the CST, while the PVST+ bridge is the root for one or more
other VLANs. A failed simulation puts the boundary port in root
inconsistent mode. "

Regards,
Ronny

Original Message:
-----------------
From: Senthil Kumar senthil.kumar@intechnology.co.uk
Date: Thu, 17 Oct 2002 20:29:22 +0100
To: ccielab@groupstudy.com
Subject: mst - pvst interoperability - will not do load balancing..isthis a
bug??

i connected a 3550 to 2924xl on a fe-100 trunk.

vlan 2, 251 on both

spann vlan 2 pri 4096 on 2900 - makes it root as it is less than the default
32768

vLAN0002
  Spanning tree enabled protocol ieee
  Root ID Priority 4098
             Address 000b.4601.8200
             This bridge is the root
             Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec

  Bridge ID Priority 4098 (priority 4096 sys-id-ext 2)
             Address 000b.4601.8200
             Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
             Aging Time 15

3550#sh span vlan 251

VLAN0251
  Spanning tree enabled protocol ieee
  Root ID Priority 32768
             Address 0050.54a1.57c6
             Cost 19
             Port 11 (GigabitEthernet0/11)
             Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec

  Bridge ID Priority 33019 (priority 32768 sys-id-ext 251)
             Address 000b.4601.8200
             Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
             Aging Time 300

---------
cool works fine.

now i want to enable mst on 3550.

3550#sh spann mst

###### MST00 vlans mapped: 1-4094
Bridge address 000b.4601.8200 priority 32768 (32768 sysid 0)
Root this switch for CST and IST
Configured hello time 2, forward delay 15, max age 20, max hops 20

Interface role state cost prio type
---------------- ---- ----- --------- ---- --------------------------------
Gi0/11 desg FWD 200000 128 P2P bound(PVST)
Gi0/12 desg FWD 200000 128 P2P

>> this switch has become the root for ist and cst.

3550#sh span vlan 2

MST00
  Spanning tree enabled protocol mstp
  Root ID Priority 32768
             Address 000b.4601.8200
             This bridge is the root
             Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec

  Bridge ID Priority 32768 (priority 32768 sys-id-ext 0)
             Address 000b.4601.8200
             Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
             Aging Time 0

>> 3550 maintained its root for vlan 2 but changed priority to 32768.

3550#sh span vlan 251

  Bridge ID Priority 32768 (priority 32768 sys-id-ext 0)
             Address 000b.4601.8200
             Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
             Aging Time 0
>> it also become root for vlan 251 - as the bridge id is same but bac is
lower than 2900.
----------

for us to keep 2900 root for vlan 251 let me change the priority to be 30000

GXC1#sh span vlan 251

Spanning tree 251 is executing the IEEE compatible Spanning Tree protocol
  Bridge Identifier has priority 32768, address 0050.54a1.57c6
  Configured hello time 2, max age 20, forward delay 15
  Current root has priority 32768, address 000b.4601.8200

GXC1#conf t
Enter configuration commands, one per line. End with CNTL/Z.
GXC1(config)#spann vlan 251 pri 30000
GXC1(config)#^Z
GXC1#
00:16:46: ST: we are the spanning tree root
00:16:46: ST: FastEthernet0/14 become designated port

GXC1#sh span vlan 251

Spanning tree 251 is executing the IEEE compatible Spanning Tree protocol
  Bridge Identifier has priority 30000, address 0050.54a1.57c6
  Configured hello time 2, max age 20, forward delay 15
  We are the root of the spanning tree

>> we acheived this..but

GXC1#sh span vlan 2

Spanning tree 2 is executing the IEEE compatible Spanning Tree protocol
  Bridge Identifier has priority 32768, address 0050.54a1.57c1
  Configured hello time 2, max age 20, forward delay 15
  We are the root of the spanning tree

this switch has also become the root of vlan 2, something that we didnt
expect

when we check the logs in 3550

00:16:35: %SPANTREE-2-PVSTSIM_FAIL: Superior PVST BPDU received on VLAN 251
port Gi0/11,
claiming root 30000:0050.54a1.57c6. Invoking root guard to block the port

00:16:35: %SPANTREE-2-ROOTGUARD_BLOCK: Root guard blocking port
GigabitEthernet0/11 on MST00.

3550#sh span vlan 2

  Bridge ID Priority 32768 (priority 32768 sys-id-ext 0)
             Address 000b.4601.8200
             Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
             Aging Time 0

3550#sh span vlan 251

  Bridge ID Priority 32768 (priority 32768 sys-id-ext 0)
             Address 000b.4601.8200
             Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
             Aging Time 0

-- now 3550 had blocked the port connected to 2900 and become itself as root
for the vlan 2 and 251.

-- so enabling a spanning tree on 3550 had broken the spanning tree between
it and another pvst switch.

>
as the option said root port guard had done this.. let me see if the option
is enabled..

3550#sh run int g0/11
Building configuration...

Current configuration : 206 bytes
!
interface GigabitEthernet0/11
description ** connection to c2900 **
switchport access vlan 251
switchport trunk encapsulation isl
switchport mode trunk
mac-address 00ff.ffff.ffff
no ip address
end

- no it is not enabled..

still may be its a default setting try and disable it

3550#conf t
Enter configuration commands, one per line. End with CNTL/Z.
3550(config)#no spann g?
% Unrecognized command
3550(config)#no spann r?
% Unrecognized command
3550(config)#int g0/11
3550(config-if)#no spann r?
% Unrecognized command
3550(config-if)#no spann guard root

- i disabled the option in port g0/11 -where it connects to 2900..

this doesnt make any change or differnce..

let me go and redo the change that i did for making 2900 the root for vlan 251 # GXC1#conf t Enter configuration commands, one per line. End with CNTL/Z. GXC1(config)#no spann vlan 251 pri 30000 -- now.. 00:23:02: %SPANTREE-2-ROOTGUARD_UNBLOCK: Root guard unblocking port GigabitEthernet0/11 on MST00.

>3500 had unblocked the port and it has become the root for both vlans as it was before.

if we assume this is because of a single instane.. mapping vlan 251 to instance 1 could help.. let me try that

3550#conf t Enter configuration commands, one per line. End with CNTL/Z. 3550(config)#span mst config 3550(config-mst)#inst 1 vlan 251

- did that

3550#sh span mst

###### MST00 vlans mapped: 1-250,252-4094 Bridge address 000b.4601.8200 priority 32768 (32768 sysid 0) Root this switch for CST and IST Configured hello time 2, forward delay 15, max age 20, max hops 20

Interface role state cost prio type ---------------- ---- ----- --------- ---- -------------------------------- Gi0/11 desg BLK 200000 128 P2P Gi0/12 desg BLK 200000 128 P2P

###### MST01 vlans mapped: 251 Bridge address 000b.4601.8200 priority 32769 (32768 sysid 1) Root this switch for MST01

Interface role state cost prio type ---------------- ---- ----- --------- ---- -------------------------------- Gi0/11 desg BLK 200000 128 P2P Gi0/12 desg BLK 200000 128 P2P

now vlan 251 is using mst-1 on 3550 and it is still the root.

3550#sh span vlan 251

MST01 Spanning tree enabled protocol mstp Root ID Priority 32769 Address 000b.4601.8200 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 000b.4601.8200 Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec Aging Time 0

-- so let me reset priority 30000 for vlan 251 in 2900 and lets see what happens..

GXC1(config)#spann vlan 251 pri 30000 GXC1(config)# 00:27:29: ST: we are the spanning tree root 00:27:29: ST: FastEthernet0/14 become designated port

00:27:18: %SPANTREE-2-PVSTSIM_FAIL: Superior PVST BPDU received on VLAN 251 port Gi0/11, claiming root 30000:0050.54a1.57c6. Invoking root guard to block the port 00:27:18: %SPANTREE-2-ROOTGUARD_BLOCK: Root guard blocking port GigabitEthernet0/11 on MST00.

the same result-- the spanning tree is broken between both swiches and they both are root for vlan 2 and vlan 251..

this is insane..

the only think i could do now is to set the switch to not talk extended mode in spanning-tree

3550(config)#no spanning-tree extend system-id

did it..

3550(config)#no spanning-tree extend system-id % Command "no spanning-tree extend system-id <cr>" was not accepted. This platform requires that the extended system-id feature remain enabled.

not helpful.. this platform wants it to be on.. this also means all priority you set should be nx4096.

-- i can do it another way.. instead of changing the priority in 2900 for vlan 251 i could change priority in 3500..i will try both mst and cst method.

GXC1(config)#no spann vlan 251 pri 30000

i reset the priority in 2900 - now spanning tree is formed and 3550 is the root for cst and ist and for vlan 2, 251.

NOW

3550(config)#spann mst 1 priority 36864 3550(config)# 00:32:57: setting bridge id (which=1) prio 36865 prio cfg 36864 sysid 1 (on) id 9001.000b.4601.8200^Z 3550# 00:32:59: %SYS-5-CONFIG_I: Configured from console by console

3550#SH SPAN VLAN 251

MST01 Spanning tree enabled protocol mstp Root ID Priority 36865 Address 000b.4601.8200 This bridge is the root Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec

Bridge ID Priority 36865 (priority 36864 sys-id-ext 1) Address 000b.4601.8200 Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec Aging Time 0

- 3550 is still the root for the vlan 251 and vlan 2.

but even when it has priority of 36865 it is seen with priority of 32768 by the 2900 switch.

GXC1(config)# 00:31:13: ST: Heard root 32768-000b.4601.8200 on FastEthernet0/14 vlan 1 00:31:13: Supersedes 32768-0050.54a1.57c0 00:31:13: ST: Heard root 32768-000b.4601.8200 on FastEthernet0/14 vlan 2 00:31:13: Supersedes 32768-0050.54a1.57c1 00:31:13: ST: Heard root 32768-000b.4601.8200 on FastEthernet0/14 vlan 5 00:31:13: Supersedes 32768-0050.54a1.57c4 00:31:13: ST: Heard root 32768-000b.4601.8200 on FastEthernet0/14 vlan 251 00:31:13: Supersedes 32768-0050.54a1.57c6

GXC1#SH SPAN VLAN 251

Spanning tree 251 is executing the IEEE compatible Spanning Tree protocol Bridge Identifier has priority 32768, address 0050.54a1.57c6 Configured hello time 2, max age 20, forward delay 15 Current root has priority 32768, address 000b.4601.8200

>>> this doesnt make any sense at all..

3550#conf t Enter configuration commands, one per line. End with CNTL/Z. 3550(config)#no spann mst 1 priority 36864 3550(config)# 00:36:57: setting bridge id (which=1) prio 32769 prio cfg 32768 sysid 1 (on) id 8001.000b.4601.8200 3550(config)#^Z

this didnt change the priority of the swith..made no change at all..

let me do it at cst on the same switch..

3550(config)#spanning-tree vlan 251 prio 61440 3550(config)#^Z 3550# 00:38:19: %SYS-5-CONFIG_I: Configured from console by console 3550# 3550# 3550# 3550#sh span mst

Interface role state cost prio type ---------------- ---- ----- --------- ---- -------------------------------- Gi0/11 desg FWD 200000 128 P2P bound(PVST) Gi0/12 desg FWD 200000 128 P2P

###### MST01 vlans mapped: 251 Bridge address 000b.4601.8200 priority 32769 (32768 sysid 1) Root this switch for MST01

Interface role state cost prio type ---------------- ---- ----- --------- ---- -------------------------------- Gi0/11 boun FWD 200000 128 P2P bound(PVST) Gi0/12 desg FWD 200000 128 P2P

3550#sh span vlan 251

MST01 Spanning tree enabled protocol mstp Root ID Priority 32769 Address 000b.4601.8200 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 000b.4601.8200 Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec Aging Time 0

Interface Port ID Designated Port ID Name Prio.Nbr Cost Sts Cost Bridge ID Prio.Nbr ---------------- -------- --------- --- --------- -------------------- -------- Gi0/11 128.11 200000 FWD 0 32769 000b.4601.8200 128.11 Gi0/12 128.12 200000 FWD 0 32769 000b.4601.8200 128.12

>> made no change at all..

but

GXC1(config)#span pri GXC1(config)#span priority 0 GXC1(config)# 00:39:52: ST: we are the spanning tree root 00:39:52: ST: FastEthernet0/14 become designated port 00:39:52: ST: Topology Change rcvd on FastEthernet0/14 vlan 1 00:39:53: ST: Topology Change rcvd on FastEthernet0/14 vlan 1

3550#sh span

MST00 Spanning tree enabled protocol mstp Root ID Priority 0 Address 0050.54a1.57c0 Cost 200000 Port 11 (GigabitEthernet0/11) Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec

Bridge ID Priority 32768 (priority 32768 sys-id-ext 0) Address 000b.4601.8200 Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec Aging Time 0

Interface Port ID Designated Port ID Name Prio.Nbr Cost Sts Cost Bridge ID Prio.Nbr ---------------- -------- --------- --- --------- -------------------- -------- Gi0/11 128.11 200000 FWD 0 0 0050.54a1.57c0 128.27 Gi0/12 128.12 200000 FWD 200000 32768 000b.4601.8200 128.12

>> a change for the vlan 1 priority in 2900 has made it root for vlan 1, and root for all mst 0 instances in 3550 this also includes vlan 2.

now i could make 2900 root for vlan 2..which is not what we wanted.. and 3550 is still the root for vlan251 and it is on instance mst-1.

so now we got a trick.. if you want to make a pvst switch to be root for any specific vlan, make sure those vlans are assigned to mst-0 (ist) on the mst switch.

MST01 Spanning tree enabled protocol mstp Root ID Priority 32769 Address 000b.4601.8200 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 000b.4601.8200 Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec Aging Time 0

GXC1#sh span vlan 2

Spanning tree 2 is executing the IEEE compatible Spanning Tree protocol Bridge Identifier has priority 32768, address 0050.54a1.57c1 Configured hello time 2, max age 20, forward delay 15 We are the root of the spanning tree

GXC1#sh span vlan 251

Spanning tree 251 is executing the IEEE compatible Spanning Tree protocol Bridge Identifier has priority 32768, address 0050.54a1.57c6 Configured hello time 2, max age 20, forward delay 15 We are the root of the spanning tree

now it is weired..

the spanning tree is running between 3550 and 2900..

2900 is the root for vlan 2 and vlan 251

3500 accepts 2900 is the root for vlan 2 (mst-0)

but it says it is the root for vlan 251..

so it i listen to the spantree vlan interface status

3550#sh span vlan 2 int g0/11 Interface Port ID Designated Port ID Name Prio.Nbr Cost Sts Cost Bridge ID Prio.Nbr ---------------- -------- --------- --- --------- -------------------- -------- Gi0/11 128.11 200000 FWD 0 0 0050.54a1.57c0 128.27 3550#sh span vlan 251 int g0/11 Interface Port ID Designated Port ID Name Prio.Nbr Cost Sts Cost Bridge ID Prio.Nbr ---------------- -------- --------- --- --------- -------------------- -------- Gi0/11 128.11 200000 FWD 0 32769 000b.4601.8200 128.11 3550# 3550# 3550#sh span int g0/11

Mst Instance Port ID Designated Port ID Name Prio.Nbr Cost Sts Cost Bridge ID Prio.Nbr ---------------- -------- --------- --- --------- -------------------- -------- MST00 128.11 200000 FWD 0 0 0050.54a1.57c0 128.27 MST01 128.11 200000 FWD 0 32769 000b.4601.8200 128.11

-- now the trunk port g0/11 is in forwarding mode for both vlans - vlan 2 and vlan 251

but

3550#sh span vlan 251

MST01 Spanning tree enabled protocol mstp Root ID Priority 32769 Address 000b.4601.8200 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 000b.4601.8200 Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec Aging Time 0

GXC1#sh span vlan 251

Spanning tree 251 is executing the IEEE compatible Spanning Tree protocol Bridge Identifier has priority 32768, address 0050.54a1.57c6 Configured hello time 2, max age 20, forward delay 15 We are the root of the spanning tree

Interface Fa0/14 (port 27) in Spanning tree 251 is FORWARDING Port path cost 19, Port priority 128 Designated root has priority 32768, address 0050.54a1.57c6 Designated bridge has priority 32768, address 0050.54a1.57c6

GXC1#sh cdp nei f0/14 Capability Codes: R - Router, T - Trans Bridge, B - Source Route Bridge S - Switch, H - Host, I - IGMP, r - Repeater

Device ID Local Intrfce Holdtme Capability Platform Port ID 3550 Fas 0/14 132 S I WS-C3550-1Gig 0/11

also

Spanning tree 2 is executing the IEEE compatible Spanning Tree protocol Bridge Identifier has priority 32768, address 0050.54a1.57c1 Configured hello time 2, max age 20, forward delay 15 We are the root of the spanning tree

MST00 Spanning tree enabled protocol mstp Root ID Priority 0 Address 0050.54a1.57c0 Cost 200000 Port 11 (GigabitEthernet0/11) Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec

>. this show what ever you set as the switch priority in 2900.. it is taken as the same for all common vlans that are present in 3550 mst-0 and in the pvst switch...

*** this doesnt make any sense... spanning tree is opeartional..but loop is formed.

the trunk between both switches are working in forward mode for both vlan.

but for vlan 2 (mst0) - 2900 is the root as it has low priority for vlan 1 (switch priority)

but for vlan 251 - 3500 and 2900 are roots...

what does this mean???

does this mean you cannot have the same vlan on both 2900 3500, when running mst on 3550 and pvst on 2900 and do load balancing..

because in this scenario either 3550 should be the root for all vlans, or 2900.

can you pls confirm this if you had tested this in your setup. i'll be thankful for any of your help in this regard..as it doesnt seem to be working right.

>>>>>>>>>>>>>>> i'm happy if i am asked to run mst on one switch and pvst on the other.. have same vlans on both..and let one bet the root.

and /or

have some more vlans on mst switch and let it not talk to any vlans in pvst switch.

or/

have seperate vlans on each switches..and let them not talk to eachother..

or/ run pvst on both..or run mst on both..

i might try with MSTP version of an os for my 2900 test switch. to see how mst helps do load balancing.

>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>...

Next message: Brian McGahan: "RE: bgp bestpath med missing-as-worst :-("
Previous message: elping: "Re: CCIE # 10474"
Messages sorted by: [ date ] [ thread ] [ subject ] [ author ] [ attachment ]

This archive was generated by hypermail 2.1.4 : Tue Nov 05 2002 - 08:35:50 GMT-3