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Webcast-Catalyst9k
New Member

RSTP loop diameter

Hi,

The IEEE recommendation is to consider a maximum diameter of seven bridges for the default STP timers, but does someone knows what is the diameter limit for RSTP ? What should we expect from a RSTP loop with a diameter more than 7 hops ? I am asking this because I have seen networks running RSTP with diameter >= 9 bridges causing not any problems.

Thks

2 REPLIES
Cisco Employee

Re: RSTP loop diameter

Hi Kian,

AFAIK the recommended network diameter of a RSTP network (802.1w) is still 7 per the specification.

HTH

Ankur

Re: RSTP loop diameter

There is no problem going beyond 7. Even for STP, 7 was extremely conservative considering current hw. RSTP more or less use the age as a hop count. You can expect the age to be incremented by one at each hop and your BPDU is going to be aged out when it reaches 20. If you don't like that, you can still increase the max-age because it will have no impact on convergence time with RSTP.

Regards,

Francois

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