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VMs on same network, only one seeing forwarded broadcast

 
kitkatneko
Occasional Contributor

VMs on same network, only one seeing forwarded broadcast

The problem: 2 VMs on the same network - vlan 1. Both's IP set as dhcp relay (ip helper) for a number of vlans (let's name a few: 1:servers, 2:workstations, 3:voip)

 

Here is the design:

1 procurve switch (A) where workstations (vlan 2) untagged on their respective vlans are

trunk between A-B, A side: tagged on vlan 1, B side: tagged on vlan 1

 

1 comware switch (B) where some servers are

trunk between B-C, B side:tagged on vlan 1, C side: untagged on vlan 1

 

1 procurve switch (C) where ESX-C hosts are. hosts being untagged on vlan 1

 

1 procurve switch (D) where other ESX-D hosts are. hosts being untagged on vlan1

trunk between A-D, A side: tagged on vlan 1, D side: unttaged on vlan 1

 

The virtual switches of all hosts is not set with any vlan for port groups.

 

VMA on host ESX-D: a windows 2012 as DHCP server

VMB on host ESX-C: a winwdows 2008 as DHCP server

 

Thanks to routing all workstations and servers can ping eachother.

VMA being an ip-helper sees bootp traffic forwarded and answers back as expected. Somehow VMB being an ip-helper is not shown anything.

 

the difference seems to be the comware on the middle, using tagged vlan on trunks.

 

yes, ip-helper ips are correct, and can be pinged from any devices on the network. ip-helpers are on vlan 1. so what I am missing?

3 REPLIES
Vince-Whirlwind
Honored Contributor

Re: VMs on same network, only one seeing forwarded broadcast

You would need to provide info about the subnets, the hosts' configured default GW, and where that address is configured in the design.

 

" B side:tagged on vlan 1, C side: untagged on vlan 1"

That's wrong.

If it's tagged on one side, it needs to be tagged on the other.

 

You should probably provide the interface configs either side of your switch-to-switch links.

 

Best not to use VLAN1 at all.

 

Seeing as you have a Comware switch in the middle, best to create a nothing-VLAN that can be the untagged VLAN on each of your switch-to-switch links, and not used by any subnet or device on your network.
The COmware interfaces should be configured as "trunks" with the PVID set to the nothing-VLAN.

kitkatneko
Occasional Contributor

Re: VMs on same network, only one seeing forwarded broadcast

you are right, I wrongly described that indeed, both ends are tagged on matching vlans.

 

All trunks are tagged for every vlan, no lacp.

 

As for default GW, all servers (on vlan 1, I wish I had seen that prior to tagging the job) are the A switch vlan 1 ip interface. Same thing for the other vlans.

 

 

I am not sure I understand the nothing-vlan idea.

Are you talking about a vlan, which replaced any PVID for trunks on comware - and hence untagged on the other side as well. a vlan that as no vlan ip interfaces?

 

Vince-Whirlwind
Honored Contributor

Re: VMs on same network, only one seeing forwarded broadcast

Yes, that's it.

 

I'm not a fundamentalist on this issue, but it is better to replace the default untagged VLAN1 on trunks with a different one, and use a different null-VLAN on each trunk, so it is recommended.