Amazing !!! Thanks maestro :) On Fri, Mar 28, 2008 at 11:30 PM, Scott Morris <[EMAIL PROTECTED]> wrote:
> Well.... Something has to be blocking, right? :) > > Look at Cat4. > > SW4 > > Port 18 (FastEthernet0/16) of VLAN0020 is blocking > Port path cost 19, Port priority 128, Port Identifier 128.18. > Designated root has priority 24596, address 001e.be93.8a80 > Designated bridge has priority 32788, address 001e.be93.b080 > Designated port id is 128.21, designated path cost 19 > Timers: message age 2, forward delay 0, hold 0 > Number of transitions to forwarding state: 2 > Link type is point-to-point by default > BPDU: sent 14887, received 3185 > > Port 21 (FastEthernet0/19) of VLAN0020 is forwarding > Port path cost 19, Port priority 128, Port Identifier 128.21. > Designated root has priority 24596, address 001e.be93.8a80 > Designated bridge has priority 32788, address 001e.be93.9b00 > Designated port id is 128.21, designated path cost 19 > Timers: message age 2, forward delay 0, hold 0 > Number of transitions to forwarding state: 1 > Link type is point-to-point by default > BPDU: sent 2, received 581 > > > Per your own show command there, the local path cost is the same, the > local port priority is the same... Port ID's are different (in case we > care) . > > Designated Root has the same MAC on both ports (this is a good thing!), > and Designated port MACs are different. Although Designated Path Cost > (received path cost) is the same. > > So the election process: > > 1. Total accumulated path cost to the root bridge. This is received cost > (designated path cost) + local path cost (Port path cost). Here, this is > equal either way. > 2. If a tie, look at received bridge-id. F0/19 = 001e.be93.9b00 whereas > F0/16 = 001e.be93.b080. Here we have two different values. Lower value > is preferred. That would be F0/19. > 3. If there were still a tie, we'd get into port cost/port-id information > but we had no need to get that far. > > Spanning tree is doing what it's supposed to! > > Cheers, > > > > Scott Morris, *CCIE**4** (R&S/ISP-Dial/Security/Service Provider) #4713, > JNCIE-M #153**, JNCIS-ER, CISSP, et al. > **CCSI/JNCI-M/JNCI-ER > *VP - Technical Training - IPexpert, Inc. > IPexpert Sr. Technical Instructor > > [EMAIL PROTECTED] > > > > Telephone: +1.810.326.1444 > Fax: +1.810.454.0130 > http://www.ipexpert.com > > > > ------------------------------ > *From:* amit chopra [mailto:[EMAIL PROTECTED] > *Sent:* Friday, March 28, 2008 1:51 PM > *To:* [email protected]; [EMAIL PROTECTED] > *Subject:* Spanning-tree election problem in SW4 > > Problem : Spanning-tree election: > > Switch topology > > SW1 (f0/16)-----------------(f0/13)--SW3 > | | > (f0/13) (f0/19) > | | > > | | > | | > | | > (f0/13) (f0/19) > | | > SW2 (f0/19)----------------(f0/16)---SW4 > > > > Guys - Can anybody help me :- The problem is that I am not able to find > out the answer why port f0/16 of SW4 is in > blocking stage towards to SW2. > > Please not the primary root for vlan 20 is SW1. The cost of all the > links is 19. > > > SW1#show spanning-tree vlan 20 > > VLAN0020 > Spanning tree enabled protocol ieee > Root ID Priority 24596 > Address 001e.be93.8a80 > This bridge is the root > Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec > > Bridge ID Priority 24596 (priority 24576 sys-id-ext 20) > Address 001e.be93.8a80 > Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec > Aging Time 15 > > Interface Role Sts Cost Prio.Nbr Type > ---------------- ---- --- --------- -------- > -------------------------------- > Fa0/13 Desg FWD 19 128.15 P2p > Fa0/16 Desg FWD 19 128.18 P2p > > > > SW2#show spanning-tree vlan 20 > > VLAN0020 > Spanning tree enabled protocol ieee > Root ID Priority 24596 > Address 001e.be93.8a80 > Cost 19 > Port 15 (FastEthernet0/13) > Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec > > Bridge ID Priority 32788 (priority 32768 sys-id-ext 20) > Address 001e.be93.b080 > Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec > Aging Time 15 > > Interface Role Sts Cost Prio.Nbr Type > ---------------- ---- --- --------- -------- > -------------------------------- > Fa0/13 Root FWD 19 128.15 P2p > Fa0/19 Desg FWD 19 128.21 P2p > > > SW3#show spanning-tree vlan 20 > > VLAN0020 > Spanning tree enabled protocol ieee > Root ID Priority 24596 > Address 001e.be93.8a80 > Cost 19 > Port 15 (FastEthernet0/13) > Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec > > Bridge ID Priority 32788 (priority 32768 sys-id-ext 20) > Address 001e.be93.9b00 > Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec > Aging Time 300 > > Interface Role Sts Cost Prio.Nbr Type > ---------------- ---- --- --------- -------- > -------------------------------- > Fa0/13 Root FWD 19 128.15 P2p > Fa0/19 Desg FWD 19 128.21 P2p > > > SW4#show spanning-tree vlan 20 > > VLAN0020 > Spanning tree enabled protocol ieee > Root ID Priority 24596 > Address 001e.be93.8a80 > Cost 38 > Port 21 (FastEthernet0/19) > Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec > > Bridge ID Priority 32788 (priority 32768 sys-id-ext 20) > Address 001e.be93.a100 > Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec > Aging Time 300 > > Interface Role Sts Cost Prio.Nbr Type > ---------------- ---- --- --------- -------- > -------------------------------- > Fa0/16 Altn BLK 19 128.18 P2p > Fa0/19 Root FWD 19 128.21 P2p > > *Here is the spanning-tree deatils for all 4 switch.* > > SW1 : > > Port 15 (FastEthernet0/13) of VLAN0020 is forwarding > Port path cost 19, Port priority 128, Port Identifier 128.15. > Designated root has priority 24596, address 001e.be93.8a80 > Designated bridge has priority 24596, address 001e.be93.8a80 > Designated port id is 128.15, designated path cost 0 > Timers: message age 0, forward delay 0, hold 0 > Number of transitions to forwarding state: 1 > Link type is point-to-point by default > BPDU: sent 18082, received 3 > Port 18 (FastEthernet0/16) of VLAN0020 is forwarding > Port path cost 19, Port priority 128, Port Identifier 128.18. > Designated root has priority 24596, address 001e.be93.8a80 > Designated bridge has priority 24596, address 001e.be93.8a80 > Designated port id is 128.18, designated path cost 0 > Timers: message age 0, forward delay 0, hold 0 > Number of transitions to forwarding state: 1 > Link type is point-to-point by default > BPDU: sent 18089, received 11 > > SW2 : > > Port 15 (FastEthernet0/13) of VLAN0020 is forwarding > Port path cost 19, Port priority 128, Port Identifier 128.15. > Designated root has priority 24596, address 001e.be93.8a80 > Designated bridge has priority 24596, address 001e.be93.8a80 > Designated port id is 128.15, designated path cost 0 > Timers: message age 2, forward delay 0, hold 0 > Number of transitions to forwarding state: 1 > Link type is point-to-point by default > BPDU: sent 3, received 18036 > > Port 21 (FastEthernet0/19) of VLAN0020 is forwarding > Port path cost 19, Port priority 128, Port Identifier 128.21. > Designated root has priority 24596, address 001e.be93.8a80 > Designated bridge has priority 32788, address 001e.be93.b080 > Designated port id is 128.21, designated path cost 19 > Timers: message age 0, forward delay 0, hold 0 > Number of transitions to forwarding state: 1 > Link type is point-to-point by default > BPDU: sent 3157, received 14887 > > > SW3 : > > Port 15 (FastEthernet0/13) of VLAN0020 is forwarding > Port path cost 19, Port priority 128, Port Identifier 128.15. > Designated root has priority 24596, address 001e.be93.8a80 > Designated bridge has priority 24596, address 001e.be93.8a80 > Designated port id is 128.18, designated path cost 0 > Timers: message age 1, forward delay 0, hold 0 > Number of transitions to forwarding state: 1 > Link type is point-to-point by default > BPDU: sent 11, received 18059 > > Port 21 (FastEthernet0/19) of VLAN0020 is forwarding > Port path cost 19, Port priority 128, Port Identifier 128.21. > Designated root has priority 24596, address 001e.be93.8a80 > Designated bridge has priority 32788, address 001e.be93.9b00 > Designated port id is 128.21, designated path cost 19 > Timers: message age 0, forward delay 0, hold 0 > Number of transitions to forwarding state: 1 > Link type is point-to-point by default > BPDU: sent 569, received 2 > SW4 > > Port 18 (FastEthernet0/16) of VLAN0020 is blocking > Port path cost 19, Port priority 128, Port Identifier 128.18. > Designated root has priority 24596, address 001e.be93.8a80 > Designated bridge has priority 32788, address 001e.be93.b080 > Designated port id is 128.21, designated path cost 19 > Timers: message age 2, forward delay 0, hold 0 > Number of transitions to forwarding state: 2 > Link type is point-to-point by default > BPDU: sent 14887, received 3185 > > Port 21 (FastEthernet0/19) of VLAN0020 is forwarding > Port path cost 19, Port priority 128, Port Identifier 128.21. > Designated root has priority 24596, address 001e.be93.8a80 > Designated bridge has priority 32788, address 001e.be93.9b00 > Designated port id is 128.21, designated path cost 19 > Timers: message age 2, forward delay 0, hold 0 > Number of transitions to forwarding state: 1 > Link type is point-to-point by default > BPDU: sent 2, received 581 > > > > > > > > > > > > > > >
