Virtual
LANs or VLANs are virtual separations within a switch that provide
distinct logical LANs that each behave if there were configured on a
separate physical switch. Some Important points about VLANS.
-
All the servers connected with in a VLAN will have same broadcasting domain, and can connect to each other directly
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Servers belongs to different VLANs has to communicate with each other using external Routing device.
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To Expand the VLAN across multiple physical switches, physical switches needs to be interconnected using links called Trunks
How VLAN knowledge Hhlps for System Administration?
The
majority of the problems that a system administrator experience, in
his daily job, are related to network Connectity. The troubleshooting
procedure for Network Connectivity issues related to any server starts
with two basic questions, and they are
- Whether the server able to connect with the servers from same VLAN?
- Whether the server able to connect with the Servers from Different VLAN?
Based
on the answers from this question, the system administrator further
troubleshoots the problem interms of cabling issues, switch connection
issues, IP related issues or gateway related issues.
How to identify the VLAN configured for a server network interface?
The
VLAN configuration happens at Switch port side, and it is completely
invisible for System administrators. But Still system admin can identify
the server network segment by using the network tracing utilities to
look at the network packets receieved by the the network interface.
some
Sample tools that can be used to identify network traffic are snoop
utility Solaris, tcpdump for linux ..etc. ( if you want to know about
the usage of snoop / tcpdump, please refer the post “Network physcial connectivity Checks for Solaris and Linux“ )
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