You may be wondering how does a packet travel from my adapter through the UCS system to the upstream switch? The following commands can help you trace out the data path of a packet.
'show service-profile circuit server x/y' will show the VIFs associated to a particular blade:
Server: 1/1
Fabric ID: A
VIF vNIC Link State Overall Status Admin Pin Oper Pin Transport
---------- ---------- ---------- -------------- ---------- ---------- ---------
41 Unknown Unknown 0/0 0/0 Unknown
9158 Up Active 0/0 0/0 Ether
964 eth0 Up Active 0/0 0/3 Ether
966 fc0 Up Active 0/0 0/0 Fc
Fabric ID: B
VIF vNIC Link State Overall Status Admin Pin Oper Pin Transport
---------- ---------- ---------- -------------- ---------- ---------- ---------
42 Unknown Unknown 0/0 0/0 Unknown
9159 Up Active 0/0 0/0 Ether
965 eth1 Up Active 0/0 0/3 Ether
967 fc1 Up Active 0/0 0/0 Fc
Using these numbers, we can search for the active border interfaces on the system in order to determine which uplink an interface is using to reach the outside world:
'connect nxos'
'show pinning border-interfaces active'
--------------------+---------+----------------------------------------
Border Interface Status SIFs
--------------------+---------+----------------------------------------
Po3 Active veth961 veth965 veth973 veth977 veth981
veth985 veth989 veth993 veth997
veth1001 veth1005 veth1009 veth1013
veth1017 veth1021 veth1025 veth1029
veth1033 veth1037 veth1041 veth1045
veth1049 veth1053 veth1057 veth1061
veth1065 veth1069 veth1073 veth1081
veth1085
Total Interfaces : 1
We can see from the output that all traffic for virtual interfaces connected to FI B are being sent out port-channel 3. We can take this even further and see which uplink in the port-channel has been hashed to carry the uplink traffic for a particular source.
The following command shows the hashing algorithm that will determine what uplink is used:
'show port-channel load-balance'
Port Channel Load-Balancing Configuration:
System: source-dest-ip
Port Channel Load-Balancing Addresses Used Per-Protocol:
Non-IP: source-dest-mac
IP: source-dest-ip source-dest-mac
With this in mind, the following command can be used to determine the uplink. The source IP and destination MAC addresses are needed to complete this command:
show port-channel load-balance forwarding-path interface port-channel 3 <src ip> <dst-ip> <src-mac> <dst-mac>
In a later post, I will document how to determine the IOM backplane ports and fabric ports that a particular server is using to reach the upstream network.
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