Hi all, I am working as a protocol / feature developer in L2 / L3 layers........I have come across equipments ( L3 switches) that have the facility of giving a MAC address to a VLAN. I would like to know what is the use of assigning a MAC address to a VLAN??? Thanks in advance Rohit
The connected device can move between ports without configuration change.
best regards Patrick
I think you need to take a step back.
There are port based VLANs in which you specify the switch ports to associate with a given VLAN. Devices connected to those ports will be in a common VLAN (provided they don't fail to meet other criteria like Cisco's Port Security).
There are MAC address based VLAN's (less common) where you associate the MAC addresses of hosts with the VLAN. The point being the host could be moved to a different port, and still access the VLAN to which its MAC address is associated.
VLANs are configured in different networks or subnets. Routing is required for devices in one VLAN to communicate with devices in another VLAN.
Your notion of IP addresses being "assigned" to VLANs instead of ports is off base.
ARP is used to resolve a hosts IP address into its corresponding MAC address.
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snipped-for-privacy@gmail.com wrote:
Yes you're right.........ARP is only for hosts and not for networks or in this case Virtual Networks i.e. VLANs....please kindly go a step further and explain then why are IP addresses assigned to VLANs and not to ports Thanks Rohit
Did you see my earlier comment - "Your notion of IP addresses being "assigned" to VLANs instead of ports is off base."?
Perhaps it is just a matter of semantics.
Hosts are assigned IP addresses, and all hosts within a given VLAN will share a common network number and mask (e.g.: 192.168.1.0 /24).
Each VLAN uses separate address space (e.g.: VLAN 1 - 192.168.1.0 /24, VLAN 2 - 192.168.2.0 /24, VLAN 3 - 192.168.3.0 /24).
Separate DHCP pools/scopes may exist, and may align with address space boundaries of VLANs.
You may see references to a VLAN interface in a switch's config. This administrative interface is assigned to a given VLAN, and is therefore on the same broadcast domain as other participants of that VLAN.
Best Regards, News Reader
I think there may be a DHCP option (82) that facilitates the communication of additional switch port information to a DHCP server. This option may provide the ability to limit the number of DHCP addresses that can be assigned to hosts on a given switch port, and perhaps control over the specific IP's that can be assigned to hosts on a given switch port. ISPs would probably be most familiar with this feature. I recommend that you research that option.
In the environments I have worked in, IP addresses have not been "assignable" to a port, only to a host connected to a port.
If you were using a port-based VLAN, and your desire was to have a specific host, on a specific port, configured with a specific IP address, then consider the following:
You could statically configure the host's IP address, and not relocate the host to a different port.
You could "reserve" an IP address in a DHCP pool (by mapping the host's MAC address to the desired IP address), and not relocate the host to a different port.
With a specific host IP address committed to a given port, you could then use that IP address in ACLs (Access Control Lists) configured on that port.
If you relocated the host, you would lose the "port to IP mapping" you were after. In addition, the host would have to be moved to another port that was assigned to the same VLAN in order to access anything.
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