combine two switches

Unanswered Question
Mar 28th, 2008

Hi, I want to connect my both 3560 switch togather.

1stswitch:

3 vlans but all server are attached to only one vlan8(ip 192.168.5.1/27

2ndswitch:3 Vlans but server are conneted to one vlan8(192.168.4.1/32

only 1st switch is connected to internet:

Requirement:

I want server with diff. subnet connected on both switches can ping each other n 192.168.4.0 series server can access internet too.

Pls. suggest a method with commands.

I have this problem too.
0 votes
  • 1
  • 2
  • 3
  • 4
  • 5
Overall Rating: 0 (0 ratings)
Loading.
Jon Marshall Fri, 03/28/2008 - 01:57

Hi

You can connect your two switches together with either

1) a L2 trunk

2) a routed P2P link.

Deciding which one to use depends on the existing setup.

You have 3 vlans on each switch. How is the routing between the vlans on each switch done ?

Jon

blue4ciscome Fri, 03/28/2008 - 02:08

I will go for L2 trunk, out of 3 vlans my production vlan is only one that's vlan 8 on both switches.

I need guidance in depth as how to trunk n any specify commands since I do not want to disturb both switch functionality

Jon Marshall Fri, 03/28/2008 - 02:16

Okay

If you trunk these switches there will be a blip while STP reconverges so you should not do this in production hours.

A L3 connection should have less effect than a L2 trunk.

Assuming we go with a L2 trunk - what are the VTP settings on the switches at the moment ? If the 3 vlans on switch1 and the 3 vlans on switch2 are different then we need to be careful otherwise we could end up deleting the vlans off one switch. So

1) Can you post a "sh vtp status" off each switch

2) Can you confirm whether yur 3560 switches are acting as purely L2 or do they route between their vlans.

Jon

blue4ciscome Fri, 03/28/2008 - 02:39

1st2S04L3CS354SD02#sh vtp status

VTP Version : 2

Configuration Revision : 2

Maximum VLANs supported locally : 1005

Number of existing VLANs : 7

VTP Operating Mode : Server

VTP Domain Name :

VTP Pruning Mode : Disabled

VTP V2 Mode : Disabled

VTP Traps Generation : Disabled

MD5 digest : 0x38 0x5C 0x38 0x49 0xE3 0x72 0x6F 0xFF

Configuration last modified by 192.168.5.19 at 3-22-93 23:46:56

Local updater ID is 97.208.97.33 on interface Vl8 (lowest numbered VLAN interface found)

2nd2S04L3CS354SD01#sh vtp status

VTP Version : 2

Configuration Revision : 2

Maximum VLANs supported locally : 1005

Number of existing VLANs : 7

VTP Operating Mode : Server

VTP Domain Name :

VTP Pruning Mode : Disabled

VTP V2 Mode : Disabled

VTP Traps Generation : Disabled

MD5 digest : 0x9D 0x72 0x08 0x56 0xE8 0x0D 0xC4 0x13

Configuration last modified by 197.208.16.27 at 6-30-93 22:52:08

Local updater ID is 197.208.16.27 on interface Vl8 (lowest numbered VLAN interface found)

let me tell you currently I am using routing(internet cloud) between both switch to connect each other .

Jon Marshall Fri, 03/28/2008 - 03:02

Thanks for this.

Apologies for all the questions but are the vlans on these 2 switches the same. The VTP shows the same configuration revision number as well.

I just want to make sure we don't break your network.

Jon

Jon Marshall Fri, 03/28/2008 - 04:24

To create a trunk

sw1

int gi0/1

switchport trunk encapsulation dot1q

switchport mode trunk

sw2

int gi0/1

switchport trunk encapsulation dot1q

switchport mode trunk

Connect using cross-over cable or fibre.

BUT - still not sure we have the full picture here. You have the same vlan number on both switches using different subnets - not really sure how you envision this routing.

And i'm still not clear on whether you want to use one of your 3560's to route between vlans or not.

Jon

blue4ciscome Fri, 03/28/2008 - 04:37

good, but I want to access vlan8(implemented) on both switches but with different ip

gojericho0 Fri, 03/28/2008 - 07:10

Hi blue4ciscome, quick question for you. Is there a reason you want VLAN 8 on different networks? If there is i think your best bet will be to use a p2p link and have a directly connected router between the two switches. Otherwise if you use a trunk I believe any broadcast traffic will transverse the switch and try to talk to any connection on VLAN 8 even if both switches have them defined as independent networks.

Someone please correct me if i'm wrong

blue4ciscome Fri, 03/28/2008 - 21:47

Yes thr is a reason for different subnets. currently I have been connected thru a router(cloud) in mid of both switch, but it increases latency since we can't afford > 0.300 MS latency between both side servers connected on both switches.

gojericho0 Sun, 03/30/2008 - 10:44

ok, so is your current setup, switch - router - router - switch between these two sites? I'm kind of confused where the trunking would come in if their are routers between the two switches

blue4ciscome Mon, 03/31/2008 - 00:08

setup is switch--router----cloud--router--switch. but thr is bandwidth limitation on router ports .. that's y I am looking to combine both switch without any router as direct trunking so that I can utilize all 1000 mbps port speed instead going thru routers.

Jon Marshall Mon, 03/31/2008 - 00:25

If you have the same vlan numbers but using different IP's then forget about a trunk. Use a L3 routed link between your 2 switches ie.

sw1

int gi0/1

no switchport

ip address 192.168.5.1 255.255.255.252

sw2

int gi0/1

no switchport

ip address 192.168.5.2 255.255.255.252

You need to make sure that the 2 switches are either running a routing protocol or you can use static routes on each switch.

Jon

blue4ciscome Mon, 03/31/2008 - 04:32

Good Jon,

one question Do I need to connect both switch phycially first for your solution to work like switch1--gi01---cross cable---gi01--switch2 ?

pls guide

Jon Marshall Mon, 03/31/2008 - 00:27

One other thing. If you haven't already you will need to enable ip routing on the switches.

Jon

blue4ciscome Mon, 03/31/2008 - 04:40

Jon,

You mean I do not need to use any trunk command on both switch ports I just attach them with a cross cable n put those ip using routing enabled on both interfaces as directed by you.. is that right all ?

Tell, finally i goona go this now..

Jon Marshall Mon, 03/31/2008 - 04:41

Yes but you need to make sure that the routing between your vlans on the switches goes via the new link.

Urfan Khaliq Thu, 04/10/2008 - 21:10

So how did it go?

Im just curious, if both switches are close to each other (im assuming they are if you will connect them via a cable) then why were they going through 2 routers and a cloud before??

Actions

This Discussion