| Ok. I don't think STP std has mentioned this propagation, As far as I know this prorogation is wrong. I think this must be a bug in Netgear switch. >>> My setup is PC1( Windows PC) ----Switch------PC2 ( Windows PC) Using Colasoft builder tool, i captured one STP packet modified the bridge priority such that it becomes root bridge , put all invalid values for timers as 255 and sent to the switch. My switch is linux PC, netgear switch and dlink switch for comparison purposes. As switch receives the better BID packet it stop advertising it self as bridge and take values of timers from root bridge which is 255 for bridge, hello and forward delay in my case. So the switch receives this packet and updates its cost, root information and sends out on another port on which PC2 is connected and where i am seeing it on wireshark with all timer values as received from root bridge. This is all fine, the only problem is, its not validating the timer values which seems a bug to me , as the timer values are defined within the limit in standard. If Netgear is doing validation of the hello timer and is putting the maximum allowed value seems fine to me and not a bug. But still, i think forward delay and max age should also be validated before accepting new BPDU as root bridge. As in linux/dlink it is not doing any validation and sending bpdu with 255 values, which is not correct as it could lead to delay of convergence time in case of root failure. In netgear switch the command display before and after are as follows: ========================================= (FSM726V3) #show spanning-tree Bridge Priority................................ 32768 Bridge Identifier.............................. 80:00:00:26:F2:AF:93:A5 Time Since Topology Change..................... 0 day 0 hr 42 min 14 sec Topology Change Count.......................... 1 Topology Change in progress.................... FALSE Designated Root................................ 80:00:00:26:F2:AF:93:A5 Root Path Cost................................. 0 Root Port Identifier........................... 00:00 Bridge Max Age................................. 20 Bridge Max Hops................................ 20 Bridge Tx Hold Count........................... 6 Bridge Forwarding Delay........................ 15 Hello Time..................................... 2 Bridge Hold Time............................... 6 CST Regional Root.............................. 80:00:00:26:F2:AF:93:A5 Regional Root Path Cost........................ 0 --More-- or (q)uit Associated FIDs Associated VLANs --------------- ---------------- 1 1 100 100 200 200 (FSM726V3) #show spanning-tree summary Spanning Tree Adminmode........... Enabled Spanning Tree Version............. IEEE 802.1d BPDU Guard Mode................... Disabled BPDU Filter Mode.................. Disabled Configuration Name................ 00-26-F2-AF-93-A5 Configuration Revision Level...... 0 Configuration Digest Key.......... 0xac36177f50283cd4b83821d8ab26de62 Configuration Format Selector..... 0 No MST instances to display. ======================================= After sending the invalid timer packet: (FSM726V3) # (FSM726V3) # (FSM726V3) #show spanning-tree summary Spanning Tree Adminmode........... Enabled Spanning Tree Version............. IEEE 802.1d BPDU Guard Mode................... Disabled BPDU Filter Mode.................. Disabled Configuration Name................ 00-26-F2-AF-93-A5 Configuration Revision Level...... 0 Configuration Digest Key.......... 0xac36177f50283cd4b83821d8ab26de62 Configuration Format Selector..... 0 No MST instances to display. (FSM726V3) #show spanning-tree Bridge Priority................................ 32768 Bridge Identifier.............................. 80:00:00:26:F2:AF:93:A5 Time Since Topology Change..................... 0 day 0 hr 0 min 12 sec Topology Change Count.......................... 2 Topology Change in progress.................... TRUE Designated Root................................ 10:00:00:20:A1:F0:88:50 Root Path Cost................................. 200004 Root Port Identifier........................... 80:01 Bridge Max Age................................. 255 Bridge Max Hops................................ 20 Bridge Tx Hold Count........................... 6 Bridge Forwarding Delay........................ 255 Hello Time..................................... 10 Bridge Hold Time............................... 6 CST Regional Root.............................. 80:00:00:26:F2:AF:93:A5 Regional Root Path Cost........................ 0 --More-- or (q)uit Associated FIDs Associated VLANs --------------- ---------------- 1 1 100 100 200 200 (FSM726V3) # ========================================= As Cisco doesnt accept this type of BPDU it means that it is a bug to be fixed on Linux, as i conclude. Please let me know if you think otherwise. Regards, Sujata --- On Fri, 6/15/12, Sasikanth babu <sasikanth.v19@xxxxxxxxx> wrote:
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