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MC-LAG Packet Flow
MC-LAG Packet Flow
Layer 2 Switching over MC-LAG
Since hosts A and B are within the same IP subnet and VLAN, host A has a directly connected route to
reach B through the outgoing interface connected to switch S1. Host A needs to determine the MAC
address of host B.
MAC Table
⇒ L
MAC
A
A
ARP Req.
PC
1
Since both hosts are in the same IP subnet, host A will send an ARP request as follows:
•
Source MAC = MAC
•
Destination MAC = ff:ff:ff:ff:ff:ff (Broadcast)
•
Target IP = IP
B
Depending on the hash algorithm or use of a fixed primary port for non-unicast traffic, switch S
select a different port of the aggregate MC-LAG A to send the ARP request. In this example, assume that
the request goes through one of the ports connected to M1 represented by L
2
Loop Prevention
•
The broadcast packet is simply flooded within the system as indicated by the arrows.
•
The MC-LAG will prevent the flooded packets received by M
being sent out its local MC-LAG ports.
•
This way, S
will not get duplicate copies of the original packet that would otherwise flow through two
2
distinct paths: S
1
3
Step 3: MAC
Learning
A
•
Switch M
will learn MAC@= MAC
1
•
Switch M
will learn MAC@= MAC
2
page 8-18
M
1
L
A 1
L
A 2
MC-LAG-A
S
1
ARP Request Over MC-LAG
A
==> M
==> S
and S
==> M
1
2
1
on the MC-LAG aggregate L
A
on the MC-LAG aggregate L
A
OmniSwitch AOS Release 7 Network Configuration Guide
Configuring Multi-chassis Link Aggregation
M
2
L
B2
L
B1
MC-LAG-B
S
2
A1
through the Virtual Fabric Link from
2
==> M
==> S
.
1
2
2
.
A
as well.
A
MAC Table
⇒ L
MAC
A
A
Host B
(MAC
, IP
)
B
B
PC
will
1
.
March 2011
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