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Portfast Behaviour

Hi Guys,

We have a 2950 running in rapid pvst mode. There are some 3 com switches connected to the first couple of ports, some running rstp and some stp. The ports are not trunk, they are access ports for vlan 4 on that floor without portfast:

show spanning-tree vlan 4

VLAN0004

Spanning tree enabled protocol rstp

Root ID Priority 4100

Address 0011.bbee.b580

Cost 4

Port 25 (GigabitEthernet0/1)

Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec

Bridge ID Priority 32772 (priority 32768 sys-id-ext 4)

Address 0012.0153.c640

Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec

Aging Time 300

Interface Role Sts Cost Prio.Nbr Type

---------------- ---- --- --------- -------- --------------------------------

Fa0/1 Desg FWD 19 128.1 P2p

Fa0/2 Desg FWD 19 128.2 P2p Peer(STP)

Fa0/3 Desg FWD 19 128.3 P2p Peer(STP)

Fa0/5 Desg FWD 19 128.5 P2p Peer(STP)

Fa0/6 Desg FWD 19 128.6 P2p

All the other ports on the 2950 is configured with portfast. However, when one of the ports configured with portfast goes to forwarding, connection to all workstations on the STP (not rstp) 3com switches are lost while STP converges and the following is seen:

.Apr 17 12:53:44: %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/9, changed state to down

.Apr 17 12:53:45: %LINK-3-UPDOWN: Interface FastEthernet0/9, changed state to down

.Apr 17 12:53:49: RSTP(4): syncing port Fa0/1

.Apr 17 12:53:49: RSTP(4): syncing port Fa0/2

.Apr 17 12:53:49: RSTP(4): syncing port Fa0/3

.Apr 17 12:53:49: RSTP(4): syncing port Fa0/5

.Apr 17 12:53:49: RSTP(4): syncing port Fa0/6

.Apr 17 12:53:49: RSTP(4): initializing port Fa0/9

.Apr 17 12:53:51: %LINK-3-UPDOWN: Interface FastEthernet0/9, changed state to up

.Apr 17 12:53:52: %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/9, changed state to up

.Apr 17 12:54:04: RSTP(4): Fa0/2 fdwhile Expired

.Apr 17 12:54:04: RSTP(4): Fa0/3 fdwhile Expired

.Apr 17 12:54:04: RSTP(4): Fa0/5 fdwhile Expired

.Apr 17 12:54:19: RSTP(4): Fa0/2 fdwhile Expired

.Apr 17 12:54:19: RSTP(4): Fa0/3 fdwhile Expired

.Apr 17 12:54:19: RSTP(4): Fa0/5 fdwhile Expired

My understanding was that portfast ports would not cause notifications, or is there something I am missing?

Thanks!

Jacques

1 REPLY
Silver

Re: Portfast Behaviour

Ports with the STP portfast feature enabled will not cause TCs when going to or from the forwarding state.

http://www.cisco.com/warp/public/473/170.html#topology_change

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