I would connect to the server or blade using the iLO or iDRAC console and adjust your network settings there to ensure that they have the correct IP, gateway, and VLAN information.  If you don't have iLO or iDRAC cabled in your environment that you could connect directly with a KVM console and look at the ESXi Management settings.

Good luck!
Tom

You will need to get access to the console, login as root, and checkout the vSwitch settings

use esxcfg-vswitch -l

~ # esxcfg-vswitch -l
Switch Name      Num Ports   Used Ports  Configured Ports  MTU     Uplinks
vSwitch0         64          20          64                1500    vmnic0,vmnic1

  PortGroup Name        VLAN ID  Used Ports  Uplinks
  Management Network    0        1           vmnic0,vmnic1
  VM Network            0        16          vmnic0,vmnic1

Switch Name      Num Ports   Used Ports  Configured Ports  MTU     Uplinks
vSwitch1         128         1           128               9000

  PortGroup Name        VLAN ID  Used Ports  Uplinks
  VLAN 2                2        0
  VLAN 5                5        0

and

esx-cfg -nics -l

~ # esxcfg-nics -l
Name    PCI           Driver      Link Speed     Duplex MAC Address       MTU    Description
vmnic0  0000:03:06.00 tg3         Up   1000Mbps  Full   00:00:00:00:44:b8 1500   Broadcom Corporation NC7782 Gigabit Server Adapter (PCI-X, 10,100,1000-T)
vmnic1  0000:03:06.01 tg3         Down 0Mbps     Half   00:00:00:00:44:b7 1500   Broadcom Corporation NC7782 Gigabit Server Adapter (PCI-X, 10,100,1000-T)

If it's ESX, post the results of the following commands when ran in the service console:
 esxcfg-nics -l
 esxcfg-vswif -l
 esxcfg-vswitch -l

They will also work om esxi if the previous post doesn't help

these commands esxcfg-nics and esxcfg-vswitch will list the NICs and vSwitches, and then we will be able to add/remove nics to switches etc

in the examples posted, the output from esx-nics -l shows the physical NICs in the server, these are labelled as:-

esxcfg-nics -l

vmnic0
vmnic1

the results from the command esxcfg-vswitch -l shows the virtual switches

I have two

vSwitch0
vSwitch1

vSwitch0 has two physical nics assocaited with it, and no nics associated with vSwitch1.

two port groups Management Network and VM Network have been created on vSwitch0

two port groups VLAN 2 and VLAN 5 have been created on vSwitch1

Realistically you probably changed the default gateway while you were configuring the new switch.  
Not that I am a mind reader, but go into the local gui and validate your configuration there.

Now if you had configured this server in a HA cluster there is the whole added situation potentially created by the isolation mode.

So is this standalone, or HA.
Can you gain access through the console to verify your management info?

-Virt

Hmm. Not sure about all this. if amending the Vswitches has caused the management interface to fail I can only see one of two causes:
a) you accidentally amended the management Vswitch.
b) you added a new vswitch which conflicts with the managemment IPs.

Quickest option is to get to the ESxi box physically. log into the console (monitor & keyboard)and log in. You can amend the IP details of the management interface there and even restart the management system without restarting the host.
If necessary, set the management network to a different IP/subnet that you KNOW is not in use. you can then connect to the ESXi via vsphere and look into what went wrong.

The vswitch that has your mananagment port group..is it a trunked vswitch or standard vmware teaming?

Thanks for all the replies.

@thomasdietrich, @hanccocka and @danm66

esxcfg-nics -l

vmnic0
vmnic1
vmnic2
vmnic3
vmnic4 (down - shutdown on interface on cisco switch)
vmnic5 (down - shutdown on interface on cisco switch)

esxcfg-vswitch -l

vSwitch0
vSwitch1 (the problems started when i created this)

vSwitch has 4 physical nics(vmnic0-3) associated with it, and vSwitch has 2 (vmnic4 and 5).

1 port group have been created on vSwitch0, including mgmt network and VM Network.
2 port groups have been created on vSwitch1.

Can I delete vSwitch1(esxcfg-vswitch -d vSwitch1)? Do I have to delete the port groups first(esxcfg-vswitch -D "VMkernel-iSCSI-1" vSwitch1)?

esxcfg-vswif: not found

@Virtalicious and @totallytonto: You are probably right, I'll double check these settings asap, It's a standalone server.

@paulsolov: It's trunked.

esxcfg-vswif: not found - it doesn't exist on ESXi

do you have any live VMs on this server?

you can do a esxcfg-vswitch -d vSwitch1)

you don't need to delete the port groups first.

if your VMs are still working through the VM Network on vSwitch0

it would seem that the Management settings have been changed as my fellow Experts stated above.

http://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=1006710

check your IP settings from the console.

F2 to examine default configuration.

see kb above.

Thanks hanccocka!

Yes, I have live VM's on the server, and they are running fine.
I'll try deleting vSwitch1 and reconfigure the ESXi mgmt network.

When running "esxcfg-vswitch -d vswitch1" i get:
Failed to remove vswitch: vswitch1, Error; PortGroup "VMkernel-iSCSI-1" on VirtualSwitch "vSwitch1" is still in use: 1 active ports, VM Kernel NIC

When running "esxcfg-vswitch -d VMkernel-iSCSI-1 i get:
Not a valid virtual switch or it is a DVSwitch: VMkernel-iSCSI-1

I've checked the Mgmt IP settings, they are correct.

Okay, it appears that vSwitch1 is in use, with an attached port group.

Can you cut and paste output from the commands, so we can check

I forgot capital D, but when I try to remove the portgroup or vswitch1, it says unable to delete, 1 active ports, VM Kernel NIC.

Need the piped output from esxcfg-vswitch -l and esxcfg-nics -l to workout what's going on here.

Add > vswitch.log to the end of line, and same with > nics.log

Just looking back the the support call here, did you also create the vmkernel iscsi port group?

Do you think it was possible this was given same ip address as management network?

Okay try the following

Esxcfg-vswitch -A test vSwitch1

Esxcfg-vswitch -D test vSwitch1

This will create a port group and delete a port group to check you can create and delete a pg, got another command coming for you to try

Thanks for the tips hanccocka.

Need the piped output from esxcfg-vswitch -l and esxcfg-nics -l to workout what's going on here.

esxcfg-vswitch -l
Switch Name Num Ports Used Ports Configured Ports MTU Uplinks
vSwitch0       64             10               64                        9000

vmnic0,vmnic1,vmnic2,vmnic3

PortGroup Name VLAN ID Used Ports Uplinks
ISCSI                   140         0                 vmnic0,vmnic1,vmnic2,vmnic3
vlan13                 13           1                 vmnic0,vmnic1,vmnic2,vmnic3
VM Machine Network149  3                 vmnic0,vmnic1,vmnic2,vmnic3
Management Network12   1                 vmnic0,vmnic1,vmnic2,vmnic3


Switch Name Num Ports Used Ports Configured Ports MTU Uplinks
vSwitch1       64             2               64                        1500

PortGroup Name VLAN ID Used Ports Uplinks
VMkernel-iSCSI-1 140       1

-----------------------------------------------------------------------------------
esxcfg-nics -l
Name PCI Driver Link Speed Duplex MAC Address MTU Description
vmnic0 03:00.00 bnx2 Up 1000Mbps Full xx:xx:xx:xx:xx:xx 9000 Broadcom Corporation NC373i Integrated Multifunction Gigabit Server Adapter
vmnic1 05:00.00 bnx2 Up 1000Mbps Full xx:xx:xx:xx:xx:xx 9000 Broadcom Corporation NC373i Integrated Multifunction Gigabit Server Adapter
vmnic2 13:00.00 e1000e Up 1000Mbps Full xx:xx:xx:xx:xx:xx 9000 Intel Corporation NC360T PCI Express Dual Port Gigabit Server Adapter
vmnic3 13:00.01 e1000e Up 1000Mbps Full xx:xx:xx:xx:xx:xx 9000 Intel Corporation NC360T PCI Express Dual Port Gigabit Server Adapter
vmnic4 0b:00.00 e1000e Down 0Mbps Full xx:xx:xx:xx:xx:xx 1500 Intel Corporation NC360T PCI Express Dual Port Gigabit Server Adapter
vmnic5 0b:00.01 e1000e Down 0Mbps Full xx:xx:xx:xx:xx:xx 1500 Intel Corporation NC360T PCI Express Dual Port Gigabit Server Adapter

Just looking back the the support call here, did you also create the vmkernel iscsi port group?

That is correct, I forgot to mention this, sorry.

Do you think it was possible this was given same ip address as management network?

Don't think so, but I could have given it a ip address in the VM Network.

Okay try the following

Esxcfg-vswitch -A test vSwitch1

Esxcfg-vswitch -D test vSwitch1

This will create a port group and delete a port group to check you can create and delete a pg, got another command coming for you to try

The portgroup was created and deleted successfully.

The vmkernel port group that you created is not being used is it, are your vms on iscsi.

I created the portgroup VMkernel-iSCSI-1 on vSwitch1, the vms are not on iSCSI.

Followed by exact port group name

as advised above, the quickest way is to use the console in person and change the management IP to ip/subnet you KNOW is free and connect using Vsphere console. once you are connected using the GUI its much easier to work out where it all went wrong. I still suspect you have used the managements IP/subnet somewhere else and caused a conflict.

As I stated above these settings can get out of whack and if HA is in play then isolation can make coming back impossible without a reboot (I have seen this STILL happens in ESXi 4.1 sadly).

So taking our advice to reconfig your management network may be a good move.

Can you get in and examine the esxcfg-info -n and take a good look at the gateway and routing sections.  This command will give you everything as VMware sees it in relation to nuts and bolts of the network configuration.

-Virt

Try the following

Esxcfg-vmknic -l to list

And -d to delete it.

This did the trick :) The new vmknic had IP in the VM Network (not sure why this should cause problems with the mgmt network?!).

Thanks for good response :)

After deleting the new vmknic I could delete the portgroup and vswitch,

And are u back in business? Can u connect?

Ah, sorry missed the first response. Glad u got it fixed, I took my iPad to meetings today so I could respond and help you!

I really appreciate your help, well earned points hanccocka :)
Have a nice weekend!

thanks, you are not the first to do this, and not the last!