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Vlan Support question

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Dec 25th, 2007
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all the swicthes support no of vlans....like for example cisco 4500 support 4096 vlans.....what does that mean........how come we can create 4096 vlans in a swicth as it has max 48 ports per blade and can fit for example 5 blades......what doe sactually mean that this swicth support this no of vlans....can some one ecplain it in plian language.....secondly we use the word instances in vlans like in rpvst every vlan has oits own instance....what does instance means i kno wthe concept of RPVST but what does instance mean......thanks in advance

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nambi_gct Tue, 12/25/2007 - 06:11
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1) Think about multiple switches chained and connected with trunk ports.You would definitely need more vlans.Think about service providers who connect their customers over an L2 network.

2) You can think of instance as a process.In other words one spanning tree process for each vlan.An anology is two people executing copy command at the same time in an unix system.This implies that you create two instances of copy command(otherwise two processes) and each has its own data to work with.



The_guroo_2 Tue, 12/25/2007 - 07:23
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Thanks nambi very nicely explained.....can u please help m ewith another thing as well....why would i make a swicth client not tranparent in my network this question was asked from me in interview......

nambi_gct Tue, 12/25/2007 - 20:51
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There can be two scenarios.

1) You want to minimise the vlan managment work.You dont want to logon to each switch and do the configuration.In this case you can have one or two vtp servers and the rest of the switches as vtp clients.

2) You want to have full control of each and every switch and what vlans are configured on them.In this case you put the switches in transparent mode.

Transparent mode avoids unintentional/intentioanal deletion of vlans in the vtp domain.For example bringing up a client with higher VTP revision number.


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