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New Member

Alot of traffic on a blocked Spanning Tree port

Hi to all!

I have two WS-C4507R (Version 12.2(25)EWA9) connected in redundancy using HSRP and i've noticed that in the ports that are blocked by spanning tree on the secondary switch are having alot of traffic, for example there are moments that a blocked interface has more than 65Mbps of traffic volume. I understand that in blocked ports there is some BPDU traffic but I don't believe it's going to be this amount. Here are some outputs of the switch:

VLAN0601

Spanning tree enabled protocol ieee

Root ID Priority 4697

Address 001b.54bd.c9c0

Cost 4

Port 129 (GigabitEthernet3/1)

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

Bridge ID Priority 4697 (priority 4096 sys-id-ext 601)

Address 001b.d473.95c0

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

Aging Time 300

Interface Role Sts Cost Prio.Nbr Type

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

Te1/1 Desg FWD 2 128.1 P2p

Gi3/1 Root FWD 4 128.129 P2p

Gi3/3 Desg FWD 4 128.131 P2p

Gi3/5 Desg FWD 4 128.133 P2p

Gi3/6 Desg FWD 4 128.134 P2p

Gi5/1 Desg FWD 4 128.257 P2p

Gi5/2 Desg FWD 4 128.258 P2p

Gi5/3 Desg FWD 4 128.259 P2p

Gi5/4 Desg FWD 4 128.260 P2p

Gi5/5 Desg FWD 4 128.261 P2p

Gi5/6 Desg FWD 4 128.262 P2p

Gi7/18 Desg FWD 4 128.402 P2p

Gi7/41 Altn BLK 4 128.425 P2p

Gi7/45 Desg FWD 4 128.429 P2p

Gi7/46 Desg FWD 4 128.430 P2p

GigabitEthernet7/41 is up, line protocol is up (connected)

Hardware is Gigabit Ethernet Port, address is 001b.d4b6.2a58 (bia 001b.d4b6.2a58)

Description: TO-DB-SWITCH1

MTU 1500 bytes, BW 1000000 Kbit, DLY 10 usec,

reliability 255/255, txload 1/255, rxload 1/255

Encapsulation ARPA, loopback not set

Keepalive set (10 sec)

Full-duplex, 1000Mb/s, link type is auto, media type is 10/100/1000-TX

input flow-control is on, output flow-control is on

ARP type: ARPA, ARP Timeout 04:00:00

Last input 00:00:00, output never, output hang never

Last clearing of "show interface" counters 24w3d

Input queue: 0/2000/0/0 (size/max/drops/flushes); Total output drops: 0

Queueing strategy: fifo

Output queue: 0/40 (size/max)

5 minute input rate 80000 bits/sec, 70 packets/sec

5 minute output rate 0 bits/sec, 0 packets/sec

1371903409 packets input, 298989812674 bytes, 0 no buffer

Received 1214261962 broadcasts (821127917 multicast)

0 runts, 0 giants, 0 throttles

0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored

0 input packets with dribble condition detected

7007883 packets output, 634785274 bytes, 0 underruns

0 output errors, 0 collisions, 0 interface resets

0 babbles, 0 late collision, 0 deferred

0 lost carrier, 0 no carrier

0 output buffer failures, 0 output buffers swapped out

I'll appreciate your help...

Thanks in advance...

4 REPLIES
New Member

Re: Alot of traffic on a blocked Spanning Tree port

This most likely a broadcast traffic. If you notice the traffic is just "input" not "output". My suggestion is to "sniff" that port and find out what kind of traffic is going thru.

Hall of Fame Super Silver

Re: Alot of traffic on a blocked Spanning Tree port

Hello,

you are right see:

1371903409 packets input, 298989812674 bytes, 0 no buffer

Received 1214261962 broadcasts (821127917 multicast)

88% of received frames are broadcast or multicast sent out by the designated port

Best Regards

Giuseppe

New Member

Re: Alot of traffic on a blocked Spanning Tree port

Hi to all!

Yes i noticed that...

Thanks for your help...

Re: Alot of traffic on a blocked Spanning Tree port

can you paste the show processes cpu on your secondary switch?

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