HP manual 195

Table 56 Comparison process and result on each device

Device	Comparison process		Configuration BPDU on
			ports after comparison
	• Port AP1 receives the configuration BPDU of Device B {1, 0,
		1, BP1}. Device A finds that the configuration BPDU of the
		local port {0, 0, 0, AP1} is superior to the received
		configuration BPDU, and it discards the received
		configuration BPDU.
	• Port AP2 receives the configuration BPDU of Device C {2, 0,		•	AP1: {0, 0, 0, AP1}
Device A		2, CP1}. Device A finds that the BPDU of the local port {0, 0,
		0, AP2} is superior to the received configuration BPDU, and	•	AP2: {0, 0, 0, AP2}
		it discards the received configuration BPDU.
	• Device A finds that both the root bridge and designated
		bridge in the configuration BPDUs of all its ports are itself, so
		it assumes itself to be the root bridge. It does not make any
		change to the configuration BPDU of each port, and it starts
		sending out configuration BPDUs periodically.
	• Port BP1 receives the configuration BPDU of Device A {0, 0,
		0, AP1}. Device B finds that the received configuration BPDU
		is superior to the configuration BPDU of the local port {1, 0,
		1, BP1}, and it updates the configuration BPDU of BP1.	• BP1: {0, 0, 0, AP1}
	•	Port BP2 receives the configuration BPDU of Device C {2, 0,
			• BP2: {1, 0, 1, BP2}
		2, CP2}. Device B finds that the configuration BPDU of the
		local port {1, 0, 1, BP2} is superior to the received
		configuration BPDU, and it discards the received
		configuration BPDU.
	• Device B compares the configuration BPDUs of all its ports,
Device B		and determines that the configuration BPDU of BP1 is the
		optimum configuration BPDU. Then, it uses BP1 as the root
		port, the configuration BPDUs of which will not be changed.
	• Based on the configuration BPDU of BP1 and the path cost		• Root port BP1: {0, 0,
		of the root port (5), Device B calculates a designated port
				0, AP1}
		configuration BPDU for BP2 {0, 5, 1, BP2}.
			•	Designated port BP2:
	•	Device B compares the calculated configuration BPDU {0, 5,
				{0, 5, 1, BP2}
		1, BP2} with the configuration BPDU of BP2. If the calculated
		BPDU is superior, BP2 will act as the designated port, and
		the configuration BPDU on this port will be replaced with the
		calculated configuration BPDU, which will be sent out
		periodically.
	• Port CP1 receives the configuration BPDU of Device A {0, 0,
		0, AP2}. Device C finds that the received configuration
		BPDU is superior to the configuration BPDU of the local port
		{2, 0, 2, CP1}, and it updates the configuration BPDU of
		CP1.	• CP1: {0, 0, 0, AP2}
Device C	•	Port CP2 receives the configuration BPDU of port BP2 of

Device B {1, 0, 1, BP2} before the configuration BPDU is	• CP2: {1, 0, 1, BP2}
updated. Device C finds that the received configuration
BPDU is superior to the configuration BPDU of the local port
{2, 0, 2, CP2}, and it updates the configuration BPDU of
CP2.

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