[c-nsp] quick spanning tree question
Cord MacLeod
cordmacleod at gmail.com
Tue Mar 30 13:22:26 EDT 2010
On Mar 29, 2010, at 11:06 PM, Yuri Bank wrote:
> What about your other TOR switch? If it has elected Switch 3 as its root, that would explain why traffic is being forwarded over that link.
There is no traffic inbound on g0/46 as shown below.
>
>
> Can we see output from your other switches?
>
>
> -Yuri
>
> On Mon, Mar 29, 2010 at 9:58 PM, Cord MacLeod <cordmacleod at gmail.com> wrote:
>
> On Mar 29, 2010, at 9:06 PM, Octavio Alvarez wrote:
>
> > On Fri, 26 Mar 2010 23:47:47 -0700, Cord MacLeod <cordmacleod at gmail.com> wrote:
> >
> >> 3 days ago traffic started showing up on the trunk port connecting my top of rack switches. Each of these switches has it's own better trunk path to the root bridge. I can't see why any traffic at all would traverse these links unless the other trunk on g0/45 was down, which it isn't. Also, spanning tree doesn't claim any topology changes.
> >
> > There's very little information. I could even think your traffic is
> > real and STP doesn't have anything to do with it.
>
> Sorry for the late reply. Here is some more information. First, the traffic is over 50mbit, I don't think it's STP. Second:
>
> switch3#show spanning-tree interface g0/46
>
> Vlan Role Sts Cost Prio.Nbr Type
> ---------------- ---- --- --------- -------- --------------------------------
> VLAN0001 Desg FWD 4 128.46 P2p
> VLAN0100 Desg FWD 4 128.46 P2p
> VLAN0101 Desg FWD 4 128.46 P2p
> VLAN0102 Altn BLK 4 128.46 P2p
> VLAN0120 Desg FWD 4 128.46 P2p
> VLAN0200 Desg FWD 4 128.46 P2p
> VLAN0231 Desg FWD 4 128.46 P2p
> VLAN0250 Desg FWD 4 128.46 P2p
> VLAN0321 Desg FWD 4 128.46 P2p
> VLAN0450 Desg FWD 4 128.46 P2p
> VLAN0777 Desg FWD 4 128.46 P2p
> VLAN0888 Desg FWD 4 128.46 P2p
>
> switch3#sh spanning-tree root
>
> Root Hello Max Fwd
> Vlan Root ID Cost Time Age Dly Root Port
> ---------------- -------------------- --------- ----- --- --- ------------
> VLAN0001 24577 0017.e0d7.e180 4 2 20 15 Gi0/45
> VLAN0100 24676 0017.e0d7.e180 4 2 20 15 Gi0/45
> VLAN0101 24677 0017.e0d7.e180 4 2 20 15 Gi0/45
> VLAN0102 20582 0018.181b.d700 7 2 20 15 Gi0/45
> VLAN0120 24696 0017.e0d7.e180 4 2 20 15 Gi0/45
> VLAN0200 24776 0017.e0d7.e180 4 2 20 15 Gi0/45
> VLAN0231 24807 0017.e0d7.e180 4 2 20 15 Gi0/45
> VLAN0250 24826 0017.e0d7.e180 4 2 20 15 Gi0/45
> VLAN0321 24897 0017.e0d7.e180 4 2 20 15 Gi0/45
> VLAN0450 25026 0017.e0d7.e180 4 2 20 15 Gi0/45
> VLAN0777 25353 0017.e0d7.e180 4 2 20 15 Gi0/45
> VLAN0888 25464 0017.e0d7.e180 4 2 20 15 Gi0/45
>
> switch3#show spanning-tree summary
> Switch is in pvst mode
> Root bridge for: none
> Extended system ID is enabled
> Portfast Default is disabled
> PortFast BPDU Guard Default is disabled
> Portfast BPDU Filter Default is disabled
> Loopguard Default is disabled
> EtherChannel misconfig guard is enabled
> UplinkFast is disabled
> BackboneFast is disabled
> Configured Pathcost method used is short
>
> Name Blocking Listening Learning Forwarding STP Active
> ---------------------- -------- --------- -------- ---------- ----------
> VLAN0001 0 0 0 2 2
> VLAN0100 0 0 0 9 9
> VLAN0101 0 0 0 2 2
> VLAN0102 1 0 0 1 2
> VLAN0120 0 0 0 19 19
> VLAN0200 0 0 0 16 16
> VLAN0231 0 0 0 2 2
> VLAN0250 0 0 0 2 2
> VLAN0321 0 0 0 5 5
> VLAN0450 0 0 0 2 2
> VLAN0777 0 0 0 2 2
> VLAN0888 0 0 0 2 2
> ---------------------- -------- --------- -------- ---------- ----------
> 12 vlans 1 0 0 64 65
>
> switch3#show int g0/46
> GigabitEthernet0/46 is up, line protocol is up (connected)
> ...
> MTU 1500 bytes, BW 1000000 Kbit, DLY 10 usec,
> reliability 255/255, txload 5/255, rxload 1/255
> Encapsulation ARPA, loopback not set
> Keepalive not set
> Full-duplex, 1000Mb/s, link type is auto, media type is 10/100/1000BaseTX
> input flow-control is off, output flow-control is unsupported
> ARP type: ARPA, ARP Timeout 04:00:00
> Last input 00:00:00, output 00:00:00, output hang never
> Last clearing of "show interface" counters never
> Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 0
> Queueing strategy: fifo
> Output queue: 0/40 (size/max)
> 5 minute input rate 0 bits/sec, 0 packets/sec
> 5 minute output rate 59995000 bits/sec, 3555 packets/sec
> 1446844033 packets input, 479111376008 bytes, 0 no buffer
> Received 35695615 broadcasts (0 multicasts)
> 0 runts, 0 giants, 0 throttles
> 0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored
> 0 watchdog, 35604297 multicast, 0 pause input
> 0 input packets with dribble condition detected
> 10988444843 packets output, 4655746445035 bytes, 0 underruns
> 0 output errors, 0 collisions, 1 interface resets
> 0 babbles, 0 late collision, 0 deferred
> 0 lost carrier, 0 no carrier, 0 PAUSE output
> 0 output buffer failures, 0 output buffers swapped out
>
>
> Does this give enough information? From my understanding of spanning tree, g0/46 should not be used for any traffic. g0/45 is the root port for all vlans.
>
>
>
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