How to configure two uplink for 3550?

[kcbell]

I am trying to use a access layer switch Cisco WS-C3550-48 and configure it with two uplink ports to the two Cisco 5500 core switches. One of the uplink would work as primary and the other uplink would work as secondary. This provides a redundancy uplink path from the access layer switch to the core switch.

Question: What is used to configure the 3550? Spanning tree or what? Please help.

 

[RookThis]

http://www.cisco.com/en/US/partner/...figuration_guide_chapter09186a008007ef45.html

http://www.cisco.com/en/US/partner/...s_configuration_example09186a008010f615.shtml

 

[kcbell]

RookThis:

Thanks for the reply. However, with my coo account as a customer, I cannot get to the "partner" area to see the examples. I got the "Unable to open //

http://...."

error message.

My question is "Is spanning tree the right method to use for two uplink but only one is working at any given time until the primary link failed then the secondary link with take over?"

kcbell

 

[rtfmdude]

bah - don't just trunk on the 2 ethernet links, aggregate them!

etherchannel config:

interface fastethernet0/1
switchport
switchport trunk encapsulation dot1q
switchport mode trunk
channel-group 1 mode on
channel-protocol pagp
!
interface fastethernet0/2
switchport
switchport trunk encapsulation dot1q
switchport mode trunk
channel-group 1 mode on
channel-protocol pagp

interface Port-channel1
switchport
switchport trunk encapsulation dot1q
switchport mode trunk

Double your pleasure, double your fun...

 

[kcbell]

rtfmdude:

I need to uplink to two separate routers. I will do etherchannel once I figured out how to do uplink to two routers. Any ideas?

kcbell

 

[rtfmdude]

kc,

looks like i need to read the freakin post! I thought you were just trunking 2 ethernets to the same device. whoops.

I think you're correct in assuming that spanning-tree is going to zap on of the ports on this 3550 once you have both links up. The config should be something like this:

3550:

int fast x/x
switchport
switchport trunk encapsulation dot1q
switchport mode trunk

int fast x/y
switchport
switchport trunk encapsulation dot1q
switchport mode trunk

on the 5500 it should be the same, unless it's set-based(i'm not a lan-switching guru). This should point you in the right direction:

http://cisco.com/en/US/products/hw/switches/ps700/products_tech_note09186a008012ecf3.shtml

Don't forget vtp, if you're using it:

http://cisco.com/en/US/tech/tk389/tk689/technologies_tech_note09186a0080094c52.shtml

 

[kcbell]

rtfmdude:

Thanks for the reply. I'll try to work on this and hopefully will remember to come back here to post my results.

kcbell

 

[kcbell]

Folks:

Following is what I did with the 3550. The two uplink went to two 1900 switches. That's why speed is 10. I am using the 1900 to prove the concept.

Port 24 is primary and port 23 is Secodary. It took about 40 seconds to switch from Primary to Secondary and about 20 seconds from Secondary back to the Primary when Primary was available again.

Port fast should be off for the uplink to the distribution layer switch.

I think what makes it works is 'cost'. Port-priority is not necessary.

!
interface FastEthernet0/23
switchport mode access
speed 10
spanning-tree vlan 1 port-priority 32
spanning-tree vlan 1 cost 18
!
interface FastEthernet0/24
switchport mode access
speed 10
spanning-tree vlan 1 port-priority 16
spanning-tree vlan 1 cost 17
!

 

[lambent]

are your distribution layer switches interconnecting each other? If yes then you can also set the "primary" distribution switch as a "primary root" of VLAN1. If you have multiple VLANs I suggest making odd VLANs as primary root on your primary switch, even VLANs as primary root on your secondary switch. In this case even when one of the uplinks fails, it won't cause interruption to all VLANs.

 

[kcbell]

lambent:

I don't have a core layer and the distribution layer has two 5500. What I am trying to do is to make the access layer switches to have two link to two 5500. If either one of the 5500 die or doing maintenance, the network is still up.

 

[lambent]

are your distribution layer switches interconnecting each other so that the access switch and your 2 5500 switches form a triangle topology?

 

[kcbell]

Yes, That is the idea!

 

[lambent]

hmm I'm not sure if 5500 supports per-vlan spanning-tree but if it supports, then you can do this

assuming you have a 5500A, 5500B and 3550 switch, and VLAN 1 to 6

1) configure 5500A as the root of VLAN 1,3,5 so that traffic for VLAN 1,3,5 from 3550 will be forwarded to 5500A as the other path is "blocked" and acts as a cold standby

2) configure 5500B as the root of VLAN 2,4,6 so that traffic for VLAN 2,4,6 from 3550 will be forwarded to 5500B as the other path is "blocked" and acts as a cold standby

not sure about the commands on 5500 but for those IOS switches, the command is like this:

switch(config)#spanning-tree vlan 1 root primary

or

switch(config)#spanning-tree vlan 1 priority 8192

The default priority is 32769. The switch with lowest priority will be the root.