Some questions

Unanswered Question
Feb 13th, 2008

Hi

1. Why use ISL and dot1q ?

2. What is the function of native VLAN ?

3. What is the diff b/w trunk and access link?

4. How to create Etherchannel and what is the purpose of use?

5. How do we check process speed and memory utilization in switch?

6. What is the conversion speed of RSTP? Exm: STP is 50 second.

7. There is a two link connected to ISP and I want to send only HTTP traffic to any one particular line what is the setup ?

8. How many times vlan has modified/changed how do we check in the switch?

9. There are 10 switchs and one switch I made has a server and other 9 switches are client and all the switches are created vlan's ,if server switch will fails ….any changes will happen ?

I have this problem too.
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Hi Manjunath,

I suggest you to remove these doubts one by one:

7. There is a two link connected to ISP and I want to send only HTTP traffic to any one particular line what is the setup ?

== use policy based routing : route maps: just chk ==> http://www.cisco.com/warp/public/732/Tech/plicy_wp.htm

This is quite easy to understand but be careful while applying route-maps/ACL's.

keep in touch for rest of the answers.

--gaurav

8. How many times vlan has modified/changed how do we check in the switch?

== In what sense do youi seek vlan modification information? The changes in VTP domain/VTP messages can be tracked through configuration revision number of the switch. Each server switch under a vtp domain has it, it represents the updated-ness of the vtp messages. higher the conf rev no. A higher conf rev no. will cause change the vtp domain/vlan database of every client.

--gaurav

5. How do we check process speed and memory utilization in switch?

== 1. Just cinfigure NetFlow in your device (at least 4500 series) and export the netflow traffic to a netflow-server. You will get a very good analysis of memory/cpu/processes/traffic etc.

2. OR, just try 'sho processes cpu history' 'sho proces memory' etc commands for live details.

--gaurav

3. What is the diff b/w trunk and access link?

==> Trunk link terminated by trunk-enabled ports, carry information of more than one vlans. The switchports which take part in trunk formation are configured to be either 'trunk--> forceful' or trunk on negotiation or request from peer port.

==> access link: just one vlan across the link, depending upon vlan association of the switchport which take part in making a access link. When you dont have vlan configured across your LAN, you prefer to have access links (just one vlan association i.e. vlan 1)

ISL and dot1q are actually two trunking protocols which multiplex the more than one vlan information across the same trunk-link.

Its the switchport configuration which decides te link to be access or trunk.

--gaurav

2. What is the function of native VLAN ?

==> Native vlan is actually a vlan which is called default vlan or teh vlan which we do not want to get tagged across the trunk. Think of a situation: you have one switch (which knows vlans/tagging) and a hub (which does not know vlans). Now you would like to connect the hub with switchport. Most definitely you would keep the corresponding switchport in default settings as hub won't be able to understand vlans associated ports (other than vlan 1 or default). So in order to make this flexibility

of using a vlan aware and vlan unaware device simultaneously, native vlan/ default vlans are used. I hope I'm clear.

--gaurav

muthumohan Fri, 02/15/2008 - 13:22

9. There are 10 switchs and one switch I made has a server and other 9 switches are client and all the switches are created vlan's ,if server switch will fails ….any changes will happen ?

Ok. I assume that you are talking about VTP servers and clients. VLANs can only be created on the switches that are VTP servers. VTP servers then pass on this VLAN information to the VTP client switches. You cannot create VLANs on a VTP client.

OK. You have created the VLANs on the VTP server and they are all propagated to the 9 clients. All is working fine. If the VTP server fails, nothing will happen to the VLANs on the clients. Client switches will function as normal. Only thing is you will not be able to make any changes to the VLANs in the VTP domain because you do not have your server anymore. If you want to make any changes to the VLAN database, configure one of the clients to be the server.

CAUTION: Be very cautious while adding a new switch to the VTP domain. If the new switch has a cofiguration revision number greater than the exisiting number in the domain, it will overwrite the existing VLAN database. See here for more information about this:

http://www.cisco.com/en/US/tech/tk389/tk689/technologies_tech_note09186a0080094c52.shtml

http://www.cisco.com/en/US/docs/switches/lan/catalyst2940/software/release/12.1_19_ea1/configuration/guide/swvtp.html#wp1223658

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