I seem to have an issue. The Root ID doesn't match when using a port-channel. Can someone help me out.
I would like to know why?
1. The root bridge MAC is showing as 6073.5c7b.e900, but the non-root thinks the MAC is 6073.5c7b.e941 (is this due to a port-channel)?
2. Why does the cost show as "3"?
3. How is the root ID and bridge ID MAC generated?
Core switch that shows the root bridge.
CGY-19-3750x-CSW1-RT#sh spanning-tree vlan 100
VLAN0100
Spanning tree enabled protocol ieee
Root ID Priority 8292
Address 6073.5c7b.e900
This bridge is the root
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Bridge ID Priority 8292 (priority 8192 sys-id-ext 100)
Address 6073.5c7b.e900
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Aging Time 300 sec
Interface Role Sts Cost Prio.Nbr Type
------------------- ---- --- --------- -------- --------------------------------
Po10 Desg FWD 4 128.584 P2p
Po11 Desg FWD 3 128.592 P2p
Po13 Desg FWD 3 128.608 P2p
Po14 Desg FWD 3 128.616 P2p
Gi2/0/23 Desg FWD 4 128.79 P2p
-----------------------------------------------------------------------------------------
-----------------------------------------------------------------------------------------
CGY-19-2960s-ASW1#show spanning vlan 100
VLAN0100
Spanning tree enabled protocol ieee
Root ID Priority 8292
Address 6073.5c7b.e900
Cost 3
Port 456 (Port-channel1)
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Bridge ID Priority 32868 (priority 32768 sys-id-ext 100)
Address 1c1d.8688.8180
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Aging Time 300 sec
Interface Role Sts Cost Prio.Nbr Type
------------------- ---- --- --------- -------- --------------------------------
Po1 Root FWD 3 128.456 P2p
CGY-19-2960s-ASW1#sh etherchannel port-channel
Port-channel: Po1
------------
Ports in the Port-channel:
Index Load Port EC state No of bits
------+------+------+------------------+-----------
0 00 Gi1/0/48 On 0
0 00 Gi2/0/48 On 0
CGY-19-2960s-ASW1#sh cdp neighbors gigabitEthernet 1/0/48 det
-------------------------
Device ID: CGY-19-3750x-CSW1-RT.o.local
Entry address(es):
IP address: 192.168.120.1
Platform: cisco WS-C3750X-24, Capabilities: Router Switch IGMP
Interface: GigabitEthernet1/0/48, Port ID (outgoing port): GigabitEthernet2/0/19
Management address(es):
IP address: 192.168.120.1
CGY-19-2960s-ASW1#sh cdp neighbors gigabitEthernet 2/0/48 det
-------------------------
Device ID: CGY-19-3750x-CSW1-RT.o.local
Entry address(es):
IP address: 192.168.120.1
Platform: cisco WS-C3750X-24, Capabilities: Router Switch IGMP
Interface: GigabitEthernet2/0/48, Port ID (outgoing port): GigabitEthernet1/0/19
Management address(es):
IP address: 192.168.120.1
CGY-19-2960s-ASW1#ping 192.168.120.1
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 192.168.120.1, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 1/5/11 ms
CGY-19-2960s-ASW1#
CGY-19-2960s-ASW1#sh arp | i 192.168.120.1
Internet 192.168.120.1 186 6073.5c7b.e941 ARPA Vlan100
Internet 192.168.120.19 - 1c1d.8688.81c1 ARPA Vlan100
