[c-nsp] 3750 Metro internal vlan allocation for loopback?

[Jared Gillis]

Hello,

I just upgraded one of my 3750ME switches from 12.2(46) (c3750me-i5k91-mz.122-46.SE.bin) to 12.2(58) (c3750me-i5k91-mz.122-58.SE2.bin) and suddenly the switch has allocated an internal vlan for the loopback address:

#show vlan internal usage 

VLAN Usage
---- --------------------
1006 Loopback1

interface Loopback1
 description Primary Management/Peering IP
 ip address a.b.c.d 255.255.255.255

This internal vlan usage did not occur on the older code, and is a problem because I've got 80+ of these out in the field, and I've manually used 1006 on almost all of them. When the router reloaded from the code upgrade, it blew away my manually configured vlan 1006.

I need to find some way to work around this new "feature". The 3750 won't let me change the vlan allocation model to start high and count down, and I can't find any way to manually assign a vlan to the loopback address.

Additionally, I am curious why this behavior changed suddenly. I can find no mention of this in Google or on Cisco's site.

Does anyone have any suggestions for this? 

Thanks,
Jared Gillis