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New Member

switching

hi!

If i've multiple L3 switches 3550 for inter vlan routing. Do i need to configure "Interface vlan XX " with IP in every L3 switches and L2 switches? or i just have to do it in one of the L3 switch?

If I've a router connected to these switches for the WAN connection to another location. Do i still need to do inter vlan routing(using subinterfaces) at the router if i already have L3 switching?

Thanks.

8 REPLIES

Re: switching

Hi

U just need to configure it on one of the L3 switches.Just configure the links of the other switches as trunk links which are connecting to this switch i.e which is permforming routing.

No u need not do any inter-vlan routing on u r router.Just assing the router in any of the vlans.Configure the a static router pointing to the SVI of the vlan in which u r router is connected.

Thanks

Mahmood

New Member

Re: switching

hi!

Will it be any problem if i add in the vlan interface in all the 3000 series switches? Any advantage or disadvantage of doing that?

If only one L3 switch is doing the routing, then what's the purpose of using L3 3000 series switches for most or all of their switches?

Does that mean that i can either add an IP in my physical switch's interface that's connected to the Router + One static route to the router interface connected to the L3 switch?(IP not in the configured vlan)

OR

Use 2 IP of the vlan created in the L3 switch for the serial link?

For this case, must the router connect to the L3 switch or any L2 switch?

Re: switching

Hi

yes you can add the vlan interface in all the switches.But it will depend on the default-gateway configured on the clients.U need to decide which switch u r going to use for intervlan routing.

U can use it for many ways.As u said u r having multiple L3 switches then why dnot u implement HSRP for your gateway redundency.

No just define the port connected to the ethernet interface of the router in any vlan.

configure static route in u r router pointing to u r internal networks to use the IP of the vlan interface in which u r router is assingned.

u can connect the router on any switch.better to connect it to the switch which is doing intervlan routing.

Thanks

Mahmood

New Member

Re: switching

Hi!

What if i;ve different vlan on different L3 switches? (eg. vlan 10-20 on L3 Switch 1 and vlan 30-40 on L3 switch 2). Will the vlan between these 2 switches be able to talk to each other without using a router?

Besides HSRP, what's the other reason of using full L3 switches in a network? for HSRP normall, i will only need 2 right?(1 active one standby).

Thanks.

Re: switching

David,

If you have different vlans on the L3 switches and you dont have a common vlan database across the network, then you have to do intervlan routing on each and every L3 switch which have different vlans. Taking you example:

On switch1, you will do inter-vlan routing for vlans 10-20 by creating the "interface vlan XXX" Layer-3 SVI for each vlan.

On switch2, you will do the same for vlan 30-40. Now, to have a communication between the switch1 and switch2 networks, you hhave to use either static routes or a routing protocol like RIP.

Depending your network design you can have multiple advantages of using a Layer3 switch. For example it can act as a router for a small network.You can have it as a distribution for a building where you will do inter-vlan routing for your vlans and have Layer-3 link to your core switch.

Let me know if you more questions.

HTH,Please rate if ti does.

-amit singh

New Member

Re: switching

Hi!

How do you configure Dynamic routing protocol such as RIP, EIGRP in a L3 Switch? Does this apply only when i need to do routing between switches? how about an standalone L3 siwtch with multiple vlan?

Thanks.

Re: switching

David,

This how you configure Routing protocol on a L2 switch.

RIP Config :

conf t

router rip

network x.x.x.x

Eigrp Config:

conf t

router eigrp 100

network x.x.x.x y.y.y.y

Please check the link below for configuring routing on 3550 switches:

http://www.cisco.com/univercd/cc/td/doc/product/lan/c3550/12225seb/scg/swiprout.htm

You need a routing protocl when you need to do routing between the switches. For example Switch1 with Vlan 10-20 and switch2 with vlans 30-40, then you need a routing protocol to have routing done between these two switches.

If you have a standalone switch with multiple vlans, you dont need a routing protocol on it. You can simply configure the L3 SVI interface to configure the inter-vlan routing on it.

HTH,

-amit singh

Re: switching

Hi

I suppose u r saying to have vlan interfaces on the different switches.if yes then u need to have link between these switches.i think u need to have a trunk link between them.

yes u r right u need to have 2 switches for HSRP.One active and other Standby.

U can make use of features link PBR etc.

Thanks

Mahmood

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