STP

Spanning Tree Protocol

Transcript

1. STP P A
 N N I
 N
 G
 R
 O T O C O L
 R E E

2. S S S S S S
3. S S S S S S
4. S S S S S S
5. S S S PC PC To:
6. S S S PC PC To:
7. S S S PC PC To:
8. S S S PC PC To:
9. S S S PC PC To: To: To: To: To: To: To: To: To: To: To: To:
10. S S S PC PC
11. STP VARIANTS
12. STP old, do not use RSTP STP, but faster MSTP does VLANs
13. STP old, do not use RSTP STP, but faster MSTP does VLANs You are here.
14. Designate a root For each switch, find the shortest path to the root For each cable, determine which end has the shorter path to root On each switch, disable all other ports that lead to root
15. Switches need to communicate.
16. Bridge Protocol Data Unit
17. S S S S
18. S S S S I am root with priority 2.
19. S S S S 2 5 4 3 2 3 4 5
20. S S S S 2 5 4 3 2 3 4 5
21. S S S S 2 5 4 2 3 4
22. S S S S 2 5 2 3 4
23. S S S S 2 2 3 4
24. S S S S 2 2 3
25. S S S S 2 2 3
26. Designate a root For each switch, find the shortest path to the root For each cable, determine which end has the shorter path to root On each switch, disable all other ports that lead to root ✓
27. BPDU FORMAT
28. Protocol ID Version Type Flags Root ID Path cost Bridge ID Port ID Age Max Age Hello Fwd Delay 2 B 1 B 1B 1 B 8 B 4 B 8 B 2 B 2 B 2 B 2 B 2 B always zero (for classic STP)
29. Protocol ID Version Type Flags Root ID Path cost Bridge ID Port ID Age Max Age Hello Fwd Delay 2 B 1 B 1B 1 B 8 B 4 B 8 B 2 B 2 B 2 B 2 B 2 B config topology change topology change ack
30. Protocol ID Version Type Flags Root ID Path cost Bridge ID Port ID Age Max Age Hello Fwd Delay 2 B 1 B 1B 1 B 8 B 4 B 8 B 2 B 2 B 2 B 2 B 2 B 2 B priority + 6 B MAC address
31. Protocol ID Version Type Flags Root ID Path cost Bridge ID Port ID Age Max Age Hello Fwd Delay 2 B 1 B 1B 1 B 8 B 4 B 8 B 2 B 2 B 2 B 2 B 2 B total “cost” to root 100 MBit/s: 200k 1 GBit/s: 20k
32. Protocol ID Version Type Flags Root ID Path cost Bridge ID Port ID Age Max Age Hello Fwd Delay 2 B 1 B 1B 1 B 8 B 4 B 8 B 2 B 2 B 2 B 2 B 2 B 2 B priority + 6 B MAC address
33. Protocol ID Version Type Flags Root ID Path cost Bridge ID Port ID Age Max Age Hello Fwd Delay 2 B 1 B 1B 1 B 8 B 4 B 8 B 2 B 2 B 2 B 2 B 2 B physical port of sender
34. Protocol ID Version Type Flags Root ID Path cost Bridge ID Port ID Age Max Age Hello Fwd Delay 2 B 1 B 1B 1 B 8 B 4 B 8 B 2 B 2 B 2 B 2 B 2 B hops since initial BPDU from root
35. Protocol ID Version Type Flags Root ID Path cost Bridge ID Port ID Age Max Age Hello Fwd Delay 2 B 1 B 1B 1 B 8 B 4 B 8 B 2 B 2 B 2 B 2 B 2 B max TTL
36. Protocol ID Version Type Flags Root ID Path cost Bridge ID Port ID Age Max Age Hello Fwd Delay 2 B 1 B 1B 1 B 8 B 4 B 8 B 2 B 2 B 2 B 2 B 2 B interval between periodic config BPDUs
37. Protocol ID Version Type Flags Root ID Path cost Bridge ID Port ID Age Max Age Hello Fwd Delay 2 B 1 B 1B 1 B 8 B 4 B 8 B 2 B 2 B 2 B 2 B 2 B time spent learning/listening
38. Designate a root For each switch, find the shortest path to the root For each cable, determine which end has the shorter path to root On each switch, disable all other ports that lead to root ✓ ✓ ✓ ✓
39. SOME TERMINOLOGY
40. RSTP PORT STATES DISCARDING Only BPDUs are transmitted. LEARNING Like DISCARDING, but learns MAC addresses. FORWARDING Regular data is transmitted.
41. RSTP PORT ROLES ROOT Best path to root bridge. DESIGNATED Points away from root. ALTERNATE Worse (and thus disabled) path to root bridge. BACKUP Leads to same segment as another DESIGNATED port.
42. ROLE ASSIGNMENTS
43. S S S S
44. S S S S 2 3 8 9
45. S S S S 2 3 8 9 20,000 20,010 10,000 10,000
46. Designate a root For each switch, find the shortest path to the root For each cable, determine which end has the shorter path to root On each switch, disable all other ports that lead to root
47. S S S S 2 3 8 9 20,000 20,010 10,000 10,000
48. S S S S 2 3 8 9 20,000 20,010 10,000 10,000 root bridge
49. Designate a root For each switch, find the shortest path to the root For each cable, determine which end has the shorter path to root On each switch, disable all other ports that lead to root
50. S S S S 2 3 8 9 20,000 20,010 10,000 10,000 root bridge R R R
51. Designate a root For each switch, find the shortest path to the root For each cable, determine which end has the shorter path to root On each switch, disable all other ports that lead to root
52. S S S S 2 3 8 9 20,000 20,010 10,000 10,000 root bridge R R R D D D D
53. Designate a root For each switch, find the shortest path to the root For each cable, determine which end has the shorter path to root On each switch, disable all other ports that lead to root
54. S S S S 2 3 8 9 20,000 20,010 10,000 10,000 root bridge R R R D D D D A
55. S S S S 2 3 8 9 20,000 20,010 10,000 10,000 root bridge R R R D D D D A port discarding
56. DEALING WITH FAILURE
57. S S S S root bridge S port discarding
58. S S S root bridge S port discarding I just lost my root port :’(
59. S S S root bridge S port discarding Now I can be root myself \o/
60. S S S root bridge S port discarding I’m root.
61. S S S root bridge S port discarding I’m root.
62. S S S root bridge S port discarding NOPE
63. S S S root bridge S port discarding NOPE
64. S S S root bridge S port discarding OK :/ TCN
65. S S S root bridge S TCN
66. S S S root bridge S TCN TCN ACK
67. S S S root bridge S TCN ACK
68. S S S root bridge S TCN ACK
69. S S S root bridge S TCN ACK
70. ALWAYS configure bridge priorities configure path costs if you have redundant links use RSTP instead of STP
71. PDU 1 SRV-2 SRV-1 SW-2 SW-4 PDU 2 SW-3 SW-1
72. SRV-2 SRV-1 SW-2 SW-4 PDU 2 SW-3 SW-1
73. That’s (R)STP. Further reading: http://blog.ine.com/wp-content/uploads/2010/04/understanding-stp-rstp-convergence.pdf http://blog.ine.com/2010/02/22/understanding-mstp/ Slides: https://speakerdeck.com/trehn/stp