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Community Member

mix PVST+ and RSTP

Hi ,

attachments is network diagram .

Cisco 6509 run PVST+,

Cisco nexus 5010 run RSTP .

S5 is root bridge .

stp loops will occur ?

https://supportwiki.cisco.com/ViewWiki/index.php/STP_loops_occur_between_the_Cisco_Catalyst_6513_Series_switch_and_the_Sun_Fire_B1600_Blade_System_chassis_switch_connected_with_redundant_links

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Hall of Fame Super Blue

Re: mix PVST+ and RSTP

Liuguiging

PVST+ and RSTP will work fine together but you need to be aware that any vlan that exists on both the 6500 and Nexus switches will revert to standard 802.1d timers ie. you lose the benefit of RSTP.

Apart from that you should be fine. One thing though, the 6500 supports RSTP, is there any reason why you cannot use RSTP on all the switches ?

Jon

5 REPLIES
Hall of Fame Super Blue

Re: mix PVST+ and RSTP

Liuguiging

PVST+ and RSTP will work fine together but you need to be aware that any vlan that exists on both the 6500 and Nexus switches will revert to standard 802.1d timers ie. you lose the benefit of RSTP.

Apart from that you should be fine. One thing though, the 6500 supports RSTP, is there any reason why you cannot use RSTP on all the switches ?

Jon

Community Member

Re: mix PVST+ and RSTP

Thanks

we run pvst+ on all the switches .

Nexus switches is belog to our ISP . they provide trunk link for us , and

they run RSTP on their newtork .

Hall of Fame Super Blue

Re: mix PVST+ and RSTP

Liuguiging

That makes sense but it is fairly trivial to upgrade your switches to use RSTP and with the topology you are using you could see real benefits if you have a link failure. RSTP reconverges within seconds rather than the 50 seconds with standard 802.1d timers.

Attached is a link to a doc on how to migrate from PVST+ to RSTP -

http://www.cisco.com/en/US/products/hw/switches/ps708/products_configuration_example09186a00807b0670.shtml

Jon

Community Member

Re: mix PVST+ and RSTP

Hi Jon,

Thanks again for your replies.

I readed the doc that i got confused .

stp detect the loop base on BPDU .

1.Cisco 6509 (non-root bridge) will not send 802.1d bpdu to Nexus .

2.Cisco 6509 (root bridge) will send 802.1d bpdu to Nexus .

3. Nexus send 802.1w BPDU to Cisco 6509 .

These will cause problem ?

when the Nexus RSTP port receive 802.1d bpdu packet ,Does it able to handle this bpdu packet ?

when the cisco 6509 PVST+ port receive 802.1w bpdu packet , how does it handle this packet ?

Re: mix PVST+ and RSTP

The interaction STP/RSTP is specified in the standard, it is not specific to Cisco (even if here, PVST modes are cisco proprietary). Basically, STP bridges drop RSTP BPDUs. As a result, they send BPDUs to their RSTP neighbors. An RSTP bridge that receives an STP BPDU know that it's connected to a legacy device and start sending STP BPDUs itself.

This mechanism will happen on a per-vlan basis with Cisco PVST/Rapid-PVST.

Regards,

Francois

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