That was for Rapid PVST+ (cisco prop). MST doesn't use such timers, besides MST0/IST (probably for compatibility outside
the region).
switch(config)#spanning-tree mst 0 root primary diameter ?
<2-7> Maximum number of bridges between any two end nodes
switch(config)#spanning-tree mst 1 root primary ?
<cr>
Keep in mind that the diameter value is just an internal IOS kind-of-macro that just changes automatically all other stp
timers according to its value. So you can configure a diameter of 7, check the produced timers and then take the risk
and increase them further.
Also 802.1D-2004 proposes some values for max-age in accordance to other timers.
2 ? (Bridge_Forward_Delay -- 1.0 seconds) >= Bridge_Max_Age
Bridge_Max_Age >= 2 ? (Bridge_Hello_Time + 1.0 seconds)
--
Tassos
Ross Vandegrift wrote on 22/05/2009 17:15:
On Thu, May 21, 2009 at 04:54:40PM +0300, Tassos Chatzithomaoglou wrote:
switch(config)#spanning-tree vlan 7 root primary ?
diameter Network diameter of this spanning tree
<cr>
switch(config)#spanning-tree vlan 7 root primary diameter ?
<2-7> Maximum number of bridges between any two end nodes
Are those are numbers for classic PVST? RST allow for larger diameter
networks because TCNs don't have to propogate to the root and then
back down. My numbers come from the MST version:
lab(config)#spanning-tree mst max-hops ?
<1-255> maximum number of hops a BPDU is valid
Ross
--
Tassos
Tassos Chatzithomaoglou wrote on 21/05/2009 16:43:
I had the impression that STP diameter defined the max number of bridges
between 2 points.
And the recommended value by the IEEE was 7 (using default timers).
--
Tassos
?????? ???????? wrote on 21/05/2009 12:25:
Definitely not more than 20 in a ring. As far as I know, IOS limits
the value of max-hops to 20. This means you can't have a BPDU
traverse more than 20 hops without being thrown away. If one pair of
switches in the ring experienced a total cut, your network would have
a diameter of 20, end to end.
this is STP limitation: MaxAge is by default 20 hops.
for IOS, you can change this value:
Switch(config)#spanning-tree vlan 1 max-age ?
<6-40> maximum number of seconds the information in a BPDU is valid
or for MST
Switch(config)#spanning-tree mst max-age ?
<6-40> maximum number of seconds the information in a BPDU is valid
value 40 is maximum bpdu hopcount for 3560 switch, for other models
there can be other upper limit.
--
wbr
sergey khalavchuk
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