The BackboneFast functionality is provided in RSTP by immediately accepting any BPDU sent by the current designated switch on a segment on our Alternate Discarding port, even if the BPDU is worse than the previously received.The UplinkFast functionality is provided in RSTP by maintaining the evidence of Alternate ports, and moving the "best" Alternate port into Root Forwarding role/state once the current root port fails.First of all, the RSTP already intrinsically contains functionalities equivalent to Cisco's UplinkFast and BackboneFast which have been developed only and solely for Cisco's STP/PVST/PVST+, not for RSTP/RPVST/RPVST+. Regarding this "STP nonsense", well, I'd say that it would all run just fine if all vendors, including Cisco, would care to implement it properly and without doing obscure optimizations or per-VLAN instantiations in times where MSTP can do its work just fine. The pleasure of being in touch with you again is all mine. Content not informative enough to draw conclusions.
Installed same failure, but all switches now configured for 802.1Dįailover, as expected, was 50 seconds upon removal of A1 to D1 link and 50 seconds upon reconnection of A1 to D1 link.ĭisabled STP altogether from 6220 uplinks to 3550s.įailover was 50 seconds upon removal of A1 to D1 link and 50 seconds upon reconnection of A1 to D1 link.ĭebug on Ciscos reveal bi-directional BPDU exchanges with 6220 during reconvergence.
Not exactly a good practice to keep an inter-switch link set for portfast.
So, I configured D1’s 6220-facing port for portfast ( spanning-tree portfast trunk) and, of course, it transitioned immediately into FWD state and dropped only one PING when I reconnected the link. So, upon reconnecting the A1 to D1 link, the 3550 port facing the 6220 has to transition to LIS and LRN and then FWD – 2xfwd delay intervals. So, there is no “agreement” created between the 3550 and the 6224. Reconnect A1 to D1 link - > over 30 seconds to reconverge (about 18 PINGs dropped with a 2 sec timeout/PING)Ĭisco’s rstp includes uplinkfast and backbonefast, Dell does not offer them, of course. Started continuous PING from A1 to SVI IP of D1ĭisconnected A1 to D1 link - > failover to D2 link pretty fast (dropped one PING) Let me post it here.Ģ Cisco 3550s at the distro layer (D1 and D2), running 12.2(35)SE5.ġ Dell 6220 access switch (A1), running 2.2.0.3.Īll connections are dot1q trunks allowing all vlans (only VLAN 10 configured)ĭot1q trunk between D1 and D2 (deliberately installed loop)Ī1 to D2 link BLK (Cisco port blocked, Dell port in ALT) I did document my lab set up for future reference. But if it does indeed exist, why does the port have to go into the LIS and LRN states? The port that does it is the DP on the RB. If I recall right, the output of the show spanning tree command on the Cisco's indicated RSTP, not STP.īut I, too, was/am under the impression that the open standard version of RSTP has similar functionality (UF and BBF) either built in or that must be configured, but I dont see any counterpart to UF and BBF that I can configure, so if it exists, it must be built-in to the code. I will do it again either today or tomorrow and run my show commands again. Anyway, I also dont remember everything I did. Most of my life involves working with exciting, bleeding edge technologies, not this STP nonsense, which should disappear once TRILL is fully evolved. I am a sales engineer and I work for a data center solutions company. As an FYI, I dont do the day-to-day network engineering stuff anymore. I labbed this up about a month ago and have had so many things on my plate that I havent had a chance to play with it further.
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