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Cisco Router Load Balancing Mechanisms

In many network topologies, there may exist multiple paths to the same destination network. When multiple routes with the same Administrative Distance are available for a particular network, a router will install all the routes (with the lowest Administrative Distance) in its routing table.

If multiple routes are installed in a Routing Table for the same destination network, the router must choose one of the routes every time a packet needs to be routed to this destination network. By choosing different routes for different packets, the router can load-balance the traffic destined for the destination network.

Cisco routers offer 2 different mechanisms to perform load-balancing across multiple routes to the same destination network. Click on the links below for details on each mechanism.

Per-packet load balancing

Per-destination load balancing

Route load-balancing is covered in detail in Course 4: Static Routes on this site.

Cisco Dynamic Trunking Protocol

Layer 2 interfaces on Cisco devices support 4 trunking administrative modes. These are access, trunk, dynamic auto and dynamic desirable.

The switchport mode access command statically configures an interface in access mode.

The switchport mode trunk command statically configures an interface in trunk mode.

Cisco's proprietary Dynamic Trunking Protocol (DTP) allows a layer 2 interface to dynamically set its trunking configuration when not statically assigned.

Click on the link below to learn more about Cisco Dynamic Trunking Protocol:

Disabling DTP - switchport nonegotiate

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