I have two pairs of ACEs, both are running redundancy. I've got shared-vlan-hostid set to different pools on both. However, it wasn't set initially, and the Admin context administrative alias IPs, as well as user contexts alias IPs, are still using the same VMAC addresses on both pairs.
ACE pair 1: 00.0b.fc.fe.1b.01
ACE pair 2: 00.0b.fc.fe.1b.01
Rebooting, removing the alias and re-adding it, removing a context, nothing seems to prevent the MAC address collisions.
Version: system: Version A3(2.2) [build 3.0(0)A3(2.2) adbuild_20:56:50-2009/04/03_/a
Has anyone seen anything like this?
When contexts share a VLAN, the ACE assigns a different MAC address to the VLAN on each context. The MAC addresses reserved for shared VLANs are 0x001243dc6b00 to 0x001243dcaaff, inclusive. All ACE modules derive these addresses from a global pool of 16k MAC addresses. This pool is divided into 16 banks, each containing 1,024 addresses. Thus, there can be 16 ACEs per subnet.
Each ACE supports 1,024 shared VLANs, and uses only one bank of MAC addresses out of the pool. Thus, a shared MAC address is associated with a shared VLAN interface.
By default, the bank of MAC addresses that the ACE uses is randomly selected at boot time. However, if you configure two ACE modules in the same Layer 2 network and they are using shared VLANs, the ACEs may select the same address bank, resulting in the use of the same MAC addresses. To avoid this conflict, you need to configure the bank that the ACEs will use.
To configure a specific bank of MAC addresses for an ACE, use the shared-vlan-hostid command in configuration mode in the Admin context. The syntax for this command is:
The number argument indicates the bank of MAC addresses that the ACE uses. Enter a number from 1 to 16. For example, to configure bank 2 of MAC addresses, enter:
host1/Admin(config)# shared-vlan-hostid 2
To remove the configured bank of MAC addresses and allow the ACE to randomly select a bank, use the no shared-vlan-hostid command. For example, enter:
host1/Admin(config)# no shared-vlan-hostid