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Default Gateway

i am a little confused about the concept of default-gateway and management ip's / VLAN's in L2 and L3 switches.

i can understand the importance of a DGW on a switch when a switch is sending traffic to its GW, but whats its role while we are accessing / telnetting into a switch.A switch doesnt allow access if its DGW is not correctly set.

What is the purpose of Management IP's / VLAN on a switch??

What do cisco means when it says that following switch is transparent ?

4 REPLIES
Hall of Fame Super Blue

Re: Default Gateway

Hi

When the switch is acting as a layer 2 switch then you can have on L3 vlan interface on that switch. So as an example

switch(config)# int vlan 1

switch(config-if)# ip address 192.168.5.2 255.255.255.0

Then you need to set the default-gateway on the switch. So in this example lets say the default-gateway is 192.168.5.1 which is on a l3 switch.

ip default-gateway 192.168.5.1

If you didn't add the gateway then you could still telnet to the switch but only from another switch/machine in the 192.168.5.0/24 network.

So if you want to manage the switch from your desktop and your desktop is in the 192.168.5.0/24 network the switch would not need a default-gateway.

But if your desktop was in a different subnet then the switch needs to know how to get to that subnet and it does that by sending traffic to it's default-gateway.

A transparent switch can mean a number of things. Can you provide some context.

Jon

Re: Default Gateway

Default-gateway is generally added on L2 switches which are not capable of doing routing. This is a way of telling them to fwd the traffic for all non-connected hosts to the DG.

Management IP's are used to manage a device i.e. you could telnet to a device from remote when you have assigned switch an IP. otherwise you need to connect thru console everytime & need to be near the device to be able to configure it.

So, DG is something to do with traffic & Managmnt IP is something to do with management.

hope that helps.

pls rate all helpful posts.

New Member

Re: Default Gateway

A L3 switch do has some IP on its physical or logical interface, through which we can telnet it.But the main purpose of using mgnt IP is that if some time the interface goes down we can access the switch via mgt IP....Am i right ??

Re: Default Gateway

The main purpose to create a separate management vlan is to separate the switch or any other device to get access by unauthorised person.

You have access lists defined for this.Some times the management valn is the native vlan which carries the sensitive traffic such as VTP STP etc.

regards,

shri :)

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