While dual-homing individual devices such as servers and top of rack switches using MLAG provides fault-tolerant, active-active connectivity across a single device pair, larger networks require two tier architectures to provide fully meshed capacity both between the spine and leaf layers of the network and for onward connection to servers. MLAG’s simple yet versatile implementation makes it possible to provide high levels of redundancy with scalability of up to 64 interfaces per channel between multiple pairs of devices enabling significant network expansion without resorting to Spanning Tree.
LAG or link aggregation is a way of bonding multiple physical links into a combined logical link. MLAG or multi-chassis link aggregation extends this capability allowing a downstream switch or host to connect to two switches configured as an MLAG domain. This provides redundancy by giving the downstream switch or host two uplink paths as well as full bandwidth utilization since the MLAG domain appears to be a single switch to Spanning Tree (STP). Because the MLAG domain appears to STP as a single switch there are no blocked ports.
There is no real difference. PEM and PS are the modules that supply power to the switch/router. In some cases they also perform the AC to DC conversion as required by some platforms.
For example, PEM was replaced by PS after it became EOL in case of 7600 routers.
End-of-Sale Product Part Number
Power Entry Module for CISCO7606 (1900W Pwr Sup)
Replacement Product Part Number
2700W AC power supply for CISCO7606
In case of some routers (10k series), the power unit is still called PEM.
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IEEE 802.3ad link aggregation enables you to group Ethernet interfaces at the physical layer to form a single link layer interface, also known as a link aggregation group (LAG) or bundle. For more information, see IEEE Standard 802.3ad, Link Aggregation.
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