You also want an ePaper? Increase the reach of your titles
YUMPU automatically turns print PDFs into web optimized ePapers that Google loves.
• Static configuration is used when connecting the switch to an external switch that does not support the<br />
exchange of LACP PDUs.<br />
A LAG can offer the following benefits:<br />
• Increased reliability and availability — if one of the physical links in the LAG goes down, traffic will<br />
be dynamically and transparently reassigned to one of the other physical links.<br />
• Better use of physical resources — traffic can be load-balanced across the physical links.<br />
• Increased bandwidth — the aggregated physical links deliver higher bandwidth than each individual<br />
link.<br />
• Incremental increase in bandwidth — A LAG may be used when a physical upgrade would produce a<br />
10-times increase in bandwidth, but only a two- or five-times increase is required.<br />
LAGs:<br />
• Behave like any other Ethernet link to a VLAN<br />
• Can be a member of a VLAN: See VLANs on page 215.<br />
• Are treated as physical ports with the same configuration parameters, spanning tree port priority, path<br />
cost, etc.<br />
• Can have a router port member, but routing will be disabled while it is a member. For information on<br />
LAG routing, see Link Aggregation on page 277 in the Routing chapter.<br />
• Can be comprised of interfaces from different units of an S-Series stack.<br />
LAG Load Distribution<br />
Traffic is distributed (load-balanced) over links in a LAG using a hashing algorithm. Since the<br />
packet-forwarding ASICs differ among the S-Series platforms, the load-balancing algorithm is also<br />
different. Currently, the CLI does not include a command to change the algorithm.<br />
• S50:<br />
IPv4 packets: The hash is based on the eXclusive OR (XOR) of the 3 least significant bits (LSB) of<br />
the source and destination IP addresses.<br />
Non-IP packets: The hash is based on the XOR of the 3 LSBs of the source and destination MAC<br />
addresses.<br />
• S50V, S50N, S25P:<br />
IPv4 and IPv6 packets: The hash is based on the XOR of the source IP (v4 or v6) address and Layer<br />
4 port with the destination IP (v4 or v6) address and Layer 4 port.<br />
Non-IP packets: The hash is based on the source and destination MAC addresses, VLAN, type,<br />
ingress ASIC, and ingress port.<br />
• S2410:<br />
All packets: The hash is based on the source and destination MAC addresses, type, VLAN, VLAN<br />
priority, and ingress port..<br />
On all platforms, MAC addresses must be learned for hashing to work. Broadcast, unknown unicast, and<br />
multicast packets are sent to a single port (the lowest numbered port) in the LAG.<br />
174 Link Aggregation
Change language