Jeffrey J. Kosowsky wrote at about 17:00:45 -0500 on Monday, January 16, 2012:
 > The laptops I back up have both a wired and wireless Ethernet
 > connection with (different) MAC addresses.
 > 
 > I use static DNS so that when the laptops are attached at home they
 > are given a fixed (known) IP address so that BackupPC can find them
 > using my /etc/hosts file.
 > 
 > On my old D-Link router, I used to assign the same static DNS address
 > to both MAC addresses so that no matter which connection was used, I
 > had the same fixed IP address.
 > 
 > The problem is that my new Verizon router does not allow the same IP
 > address to be correlated with different MAC addresses.
 > 
 > So now it seems that I can only match the laptop name (used by
 > BackupPC) against only one of the IP addresses so that it will only
 > get backed up on one of the two interfaces?
 > 
 > Is there any simple way to overcome this problem?
 > 
 > For example would it be possible to match 2 IP/names addresses against
 > the same host backup so that if one fails then it tries the other?
 > (this is in a sense the opposite of ClientNameAlias that allows you to
 > map multiple hosts to one IP address)
 > 

Just was thinking that the following simple hack should probably
work...

1. Set up two different static IPs, one for each network interface.
2. Enter both IPs (or equivalent names as defined in /etc/hosts) in
   the BackupPC/hosts file -- call them 'hostA' and 'hostB'
3. Create a *symlink* from TopDir/pc/hostB to TopDir/pc/hostA

Then whenever the *common* backup host ages, BackupPC will launch a
new backup -- either hostA or hostB depending on which NIC is
currently active (note: I am assuming that only one interface is
active at a time). That way if one IP addressdidn't back up then the
other would back up in place using the same history of numbered full
and incremental backups. Once either backup completed then both hosts
would look updated since they both point to the same common pc host
subdirectory of backups. Note that the host name doesn't appear at all
except as the name of the top level directory in the pc tree, so it
makes no difference whether the backup is initiated as hostA or
hostB.

The only potential issue would be collisions but even that typically shouldn't
happen since I assume that only one IP address is ever active at one
time. Potentially there might be issues if the user switched interfaces in
the middle of a backup before the first version complete or timed out
but hopefully the new backup would catch the other as a partial backup
and either continue from there or erase it... still I imagine there
could be weird edge cases though they would only occur if you switched
network interfaces mid-backup...


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