10-13-2018 08:50 PM
According to the Cisco Nexus 5000 Series NX-OS Software Configuration Guide -
Port channels provide load balancing by default and the basic configuration uses the following criteria to select the link:
- For a Layer 2 frame, it uses the source and destination MAC addresses.
- For a Layer 3 frame, it uses the source and destination MAC addresses and the source and destination IP addresses.
- For a Layer 4 frame, it uses the source and destination MAC addresses, the source and destination IP addresses, and the source and destination port number.
My question is, how is the frame determined/classified as layer 2, 3 or 4? Or is it determined based on the configured load-balancing algorithm - src-dst-mac, src-dst-ip, src-dst-port?
10-14-2018 11:00 PM
Hello,
The frame type is determined by the Forwarding Engine based on an in-line lookup on the frame self. The FE has full visibility about all the header bits(payload as well but it's not relevant) so it can perform a logic computation to determine what kind of traffic that frame is transporting.
Based on this result it will apply the chosen hashing algorithm.
HTH,
ADP
10-15-2018 06:48 PM
Cisco NX-OS load balances traffic across all operational interfaces in a port channel by reducing part of the binary pattern formed from the addresses in the frame to a numerical value that selects one of the links in the channel. Port channels provide load balancing by default.
The basic configuration uses the following criteria to select the link:
For a Layer 2 frame, it uses the source and destination MAC addresses.
For a Layer 3 frame, it uses the source and destination MAC addresses and the source and destination IP addresses.
For a Layer 4 frame, it uses the source and destination MAC addresses and the source and destination IP addresses.
You have the option to include the source and destination port number for the Layer 4 frame.
For more details please refer the link below:-
https://www.cisco.com/c/en/us/td/docs/switches/datacenter/nexus5000/sw/interfaces/521_N11/b_5k_Interfaces_Config_Guide_Release_521N11/b_5k_Interfaces_Config_Guide_Release_521N11_chapter_0100.html
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