port-channel flapping when two more links are added!?

[m-abooali]

Hello,

I have two Core 6509E SUP2T configued as VSS and has two 48 ports fiber blades. I have two 3750s, I have two gig on each 3750 port-channle to po1 and connected to both the core, one link to each core.

Now, I was asked ot add two more links on each 3750 switch to make it a total of 4 gigs on each 3750s (all 4 gig ports/uplinks will be in used an dtwo links to core one an dtwo links to core 2).

when i added two additional links on 3750s and bundled them to po1, I created another port channel on core and bundeled the additional two gigs on each core to accomodate for the two additional links (ports on core switches are not consequtives).

adding these two additional ports makes the 3750 switches flap between managemnet vlan and po1.

now, i am not sure if I must have added the two additional links on the core to teh current port-channel or core!? I have created another port-channel on core to accomodate for this currently!?

any thoughts on this is greatly appreciated.

Thanks,

Masood

[Reza Sharifi · Accepted solution]

do you think I must use Gi1/1/22 and Gi1/1/22 or any available gig interfaces on the core fiber blade will do?

No, they don't have to be consecutive, they can be any interface from the module, but if you can keep it consecutive, it makes it easier to remember.

The only restirication is that you can not have links with different speed in a portchannel.

example

you can't have a portchannel with one 1Gig interface and one 10Gig interface.  All interfaces in a portchannel must have the same speed and duplex.

HTH

[m-abooali]

Thank you Reza. I will keep you posted.

This is what i wanted to hear. I have all as 1 gig interfaces with all other parameters the same. this makes my job easier. they just decided to have two additional links all the suddent! I have no choice but to make these 4 uplinks NOT Consequtive but conventions are kept on the rest.

I really appreciate your help this late at night!.

Best Regards,

Masood

[Reza Sharifi]

No problem Masood.  Glad to help

I hope, everything goes well for you

Good Luck and keep me posted

Reza

[m-abooali]

Dear Reza,

I have not tried the stuff we discussed today because I have faced a different problem and this must get resolved before I can work on the stuff we discussed last night.

Building A has two core 6509s SUP 2T, VSS pair and large number of stacks 3750s.

Building B has a stack of two 3750s with 12 port Fiber blades which is acting as Distro or Core for Building B. this stack has three switches, single switch 3750s hanging off it.

So, when I don't have the link between the two buildings, each building cores switch can ping all other closets and vice versa.

The link between the two bulding is between Bulding A 6506 VSS pair int gi 1/1/23 and 2/1/23 and on teh core/dtsro for building B on int gi 1/1/4 and int go 2/1/4 over PO 41 (same at both ends of these two links).

one of the Links Fiber was bad so one link doesn't work until we chnage the fiber which has been ordered tomorrow first thing.

when I have link connected, some closet switches ping not working (three of 4 closets) but when I remove or disconnect this one active link, each building core can ping everwhere and Vice Versa.

It is my understanding at this point that may be the Spanning-Tree is blocking the return signal for the ping so ping doesn't know how to get back to the ping originating device. I beleive that replacing the bad fiber link with a good one must resolve this issue!? but yet to be seen!?

I was wondering what you cna please tell me about this situation?

what can i check as for Spanning-Tree (has been left at default) to see what uplink has been placed in blocking mode?

what wopuld be the best commands to check so this and sould it be on teh main Core VSS pair or the core/distro on Buildinig B or both?

Please advise,

Best Regards,

Masood

[Reza Sharifi]

Hi Masood,

How are the switches in the closets connected to the distro/core switches in building B?  If each switch in the closet has 2 uplinks to a none vss pair of switches (I know you have vss in one building), than you need to run spanning tree.

Can you provide a diagram showing how physically the switches in different building connected to core?

Also, is VSS configured correctly in building A?  If VSS is configured incorrectly, there can spanning tree issues.

Can you post the vss config and also post the output of

sh switch virt

Reza

[m-abooali]

Reza,

switches in building B use Po3, po4 and PO26 each on uplinks

int gi 1/1/1 and int gi 1/1/4 boundled to coressponding Port-channel listed above and cna be seen in config below:

Current configuration : 4491 bytes

!

! Last configuration change at 20:39:48 UTC Wed May 5 1993

!

version 15.0

no service pad

service timestamps debug datetime msec

service timestamps log datetime msec

no service password-encryption

!

hostname Building B

!

boot-start-marker

boot-end-marker

!

!

no aaa new-model

switch 1 provision ws-c3750x-12s

switch 2 provision ws-c3750x-12s

system mtu routing 1500

ip routing

!

!

!

!

!

!

!

!

spanning-tree mode pvst

spanning-tree extend system-id

!

!

!

!

vlan internal allocation policy ascending

!

!

!

!

!

!

interface Port-channel41

description to Port-channel for uplinks to Closets BUILDING a CORE vsS PAIR

switchport trunk encapsulation dot1q

switchport mode trunk

shutdown

!

interface Port-channel3

switchport trunk encapsulation dot1q

switchport mode trunk

!

interface Port-channel4

switchport trunk encapsulation dot1q

switchport mode trunk

!

interface Port-channel26

switchport trunk encapsulation dot1q

switchport mode trunk

!

interface FastEthernet0

no ip address

no ip route-cache

shutdown

!

interface GigabitEthernet1/0/1

description uplink to floor 9 Gi1/1/1

switchport trunk encapsulation dot1q

switchport mode trunk

channel-group 4 mode on

!

interface GigabitEthernet1/0/2

description uplink to floor 25 Gi1/1/1

switchport trunk encapsulation dot1q

switchport mode trunk

channel-group 3 mode on

!

interface GigabitEthernet1/0/3

description uplink to floor 26 Gi1/1/1

switchport trunk encapsulation dot1q

switchport mode trunk

channel-group 26 mode on

!

interface GigabitEthernet1/0/4

!

interface GigabitEthernet1/0/5

!

interface GigabitEthernet1/0/6

!

interface GigabitEthernet1/0/7

!

interface GigabitEthernet1/0/8

!

interface GigabitEthernet1/0/9

!

interface GigabitEthernet1/0/10

!

interface GigabitEthernet1/0/11

!

interface GigabitEthernet1/0/12

!

interface GigabitEthernet1/1/1

!

interface GigabitEthernet1/1/2

!

interface GigabitEthernet1/1/3

!

interface GigabitEthernet1/1/4

description UPLINK to Core-6509

switchport trunk encapsulation dot1q

switchport mode trunk

channel-group 41 mode on

!

interface TenGigabitEthernet1/1/1

!

interface TenGigabitEthernet1/1/2

!

interface GigabitEthernet2/0/1

description uplink to floor 9 to Gi1/1/4

channel-group 4 mode on

!

interface GigabitEthernet2/0/2

description uplink to floor 25 Gi1/1/4

channel-group 3 mode on

!

interface GigabitEthernet2/0/3

description uplink to floor 26 Gi1/1/4

channel-group 26 mode on

!

interface GigabitEthernet2/0/4

!

interface GigabitEthernet2/0/5

!

interface GigabitEthernet2/0/6

!

interface GigabitEthernet2/0/7

!

interface GigabitEthernet2/0/8

!

interface GigabitEthernet2/0/9

!

interface GigabitEthernet2/0/10

!

interface GigabitEthernet2/0/11

!

interface GigabitEthernet2/0/12

!

interface GigabitEthernet2/1/1

shutdown

channel-group 1 mode on

!

interface GigabitEthernet2/1/2

!

interface GigabitEthernet2/1/3

!

interface GigabitEthernet2/1/4

description UPLINK to Core-6509

switchport trunk encapsulation dot1q

switchport mode trunk

channel-group 41 mode on

!

interface TenGigabitEthernet2/1/1

!

interface TenGigabitEthernet2/1/2

!

interface Vlan1

no ip address

shutdown

!

interface Vlan50

description Data_SW-MGMT

ip address 156.x.x.55 255.255.255.128

!

ip http server

ip http secure-server

!

!

!DEFAULT GATEWAY TO ALL WHICHIS VSS IP ADDRESS

ip route 0.0.0.0 0.0.0.0 156.x.x.1

!

logging esm config

!

banner motd ^C

.^C

!

line con 0

password XXXX

login

line vty 0 4

passwordXXXX

login

line vty 5 15

login

!

end

Also, I am having problem ooening a Viso that i had created for this Building B.

it shows how core stack with 12 port fiber blade in each (config above) connecte to three switches hanging off it and to the VSS pair in Building A which is over PO41 and uplinks int gi 1/1/4 and int gi 2/1/4.

we have left Spanning-tree as default.

if it has to be configured, can you please tell me where and how?

Regards,

Masood

[m-abooali]

[m-abooali]

Reza,

can the distro switches uplink be connected to the vSs pair as VLAN 50 access? instead of trunk?

Thanks,

Masood

[Reza Sharifi]

Masood,

Can the distro switches uplink be connected to the vSs pair as VLAN 50 access? instead of trunk?

No, because if you have multiple vlan connecting from building B to building A that that link needs to be trunk.

Looking at you diagram since the 2 12 port 3750s are stacked and you are using portchannel from each switch to the stack, I don't see any loop.  Right now all the SVIs for all the vlans are located on the VSS and since the default gateway for all switches is vss.

One thing I can suggest is that you can terminate all the SVIs for building B on the 3750 stack and also terminate all SVIs for building A on the 6500 VSS.  Than have a layer-3 link between the 6500 and the 3750 stack.  This will basically keep each building on their own and if the connection between the 2 building go down, the vlans in each building can locally communicate. Also, you don't have to worry about spanning tree at all.

Reza

[m-abooali]

Dear Reza,

I see what you are suggesting and that was what i initially suggested too but we are only responsible for L1 and L2 including the L3 SVIs and a whole different team that I don;t know will do L3 routing + Voice.

Unfortunately I have to deal with it as is , a trunk and Spanning-Tree, i would hope that adding the second uplink to building B from VSs pair would resolve the blocking!?

if I need to configure the Spanning-Tree, based on what you so far know from the stuff I sent an dfrom what we have discussed where and how you would suggest for me to have the Spanning-tree (basic to allow not any blockig) configured?

bare minimum.

this will help me alot as I only need to show I can ping everywhere back and forth and I will be done!.

Best Regards,

Masood

[m-abooali]

Hi Reza,

if I wanted to set spanning-tree, should I do it per vlan?

is there a way to make 6509 root (say with lower priority) so it stay sroot no matter what fro all vlans?

Thanks,

Masood

[m-abooali]

Reza,

I added these gog interfaces to po1 on both 3750s

interface GigabitEthernet1/1/2

switchport trunk encapsulation dot1q

shutdown

!

interface GigabitEthernet1/1/3

switchport trunk encapsulation dot1q

shutdown

and added respective uplinks on teh cores like gi1/1/17 and 1/1/18 and 2/1/17 and 2/1/18 on core and boundled to po5 and po6. that was all I did and it brok teh system.

Thanks,

Masood