Netw206 Wek 5

A loop has 2 or more switches interconnected by a minimum of 2 physical links. This occurs when one is trying to create a redundant network and accidentally (or purposefully) creates a loop path. This compromises network integrity and presents a few problems:

1) MAC address instability: Switches are constantly updating their MAC address tables and a loop can cause one or more to appear unreachable.

2) 2) Frame Duplication: Because multiple paths can lead to a single MAC address, a frame could become a duplicate, which would send all paths back to that MAC.

These issues can be addressed by applying an STP and implementing VLANs that use VTP protocols. By separating large layer domains into smaller ones, VLANS will improve network performance. By using the STP roots for VLANs, they will follow the basic rules of spanning STP. MAC address will also be used as the priority and the switch with the lowest ID will become the root.

Using Rapid VLAN mode is recommended because it supports path redundancy and reduces undesirable loops so it improves convergence time. Running RPVST also can fall back to 802.1D when accessing legacy STP switches.

With these protocols applied, a highly available network topology will utilize STP and UDLD. STP will block interface to loop free topologies in redundant networks. IEEE 802.1Q is recommended for trunking needs as it will be backwards compatible for above mentioned legacy STP switches.

An ether channel will provide bundling of individual Ethernet links into a single logical link that provides bandwidth of 8 physical links.

References

http://www.cisco.com/c/en/us/products/collateral/switches/catalyst-6500-series-switches/prod_white_paper0900aecd805457cc.html

http://www.cisco.com/c/en/us/td/docs/switches/metro/me3400/software/release/12-2_60_ez/configuration/guide/ME3400_scg/swethchl.html...