OSPF Virtual Link

In OSPF Multi Area, all area must be connected to the backbone area (area 0), in order to communicate each other. Inter area routing will through the backbone area (area 0). If there’s area that isn’t connected to the backbone area we can setup a virtual link.

OSPF, Virtual Link, Cisco, Routing Protocol, GNS3

Based on topology above, area 2 doesn’t have connection/route to other area, since it’s not connected to the backbone area (area 0).

In this case, we can setup a Virtual Link from R4 to R2 and vice versa, from R2 to R4.

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EtherChannel – Port Link Aggregation

EtherChannel or other vendors call this Smartgroup, is  a port link aggregation technology. In other words, a technology which is used to combine several physical links between switches or routers into one logical connection and treat them as single link.

A connection with a single link.

switch, etherchannel

Add another link to get more than 1 Gbps will not work, because Spanning-tree protocol (STP) will block redundant links to prevent a loop.

etherchannel, stp, spanning-tree

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Configuring an EtherChannel Link

etherchannel

Here’s an example of EtherChannel configuration.

SW1 SW2
Port fa0/21 to port fa0/21 SW2 Port fa0/21 to port fa0/21 SW1
Port fa0/22 to port fa0/22 SW2 Port fa0/22 to port fa0/22 SW1
Port fa0/23 to port fa0/23 SW2 Port fa0/23 to port fa0/23 SW1
Port fa0/24 to port fa0/24 SW2 Port fa0/24 to port fa0/24 SW1
Port fa0/1 to PC1 Port fa0/1 to PC3
Port fa0/2 to PC2 Port fa0/2 to PC4

PC1 : 10.10.10.1/24 – VLAN 10
PC2 : 10.10.20.1/24 – VLAN 20
PC3 : 10.10.10.2/24 – VLAN 10
PC4 : 10.10.20.2/24 – VLAN 20

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