Last year, I posted a couple of articles on configuring and managing Cisco MDS Fibre Channel zones via the CLI:
New User’s Guide to Configuring Cisco MDS Zones via CLI
New User’s Guide to Managing Cisco MDS Zones via CLI
In those posts, I discussed the use of the fcalias command to create aliases for World Wide Port Names (WWPNs) on the fabric. A couple of people suggested via Twitter and blog comments that I should use device aliases instead of the the fcalias command. As a follow up to those posts, here is some information on using device aliases on a Cisco MDS Fibre Channel switch.
To create a device alias, you’ll use the device-alias database command in global configuration mode. Once you are in database configuration mode, you can create device aliases using the device-alias command, like this:
mds(config)# device-alias database
mds(config-device-alias-db)# device-alias name <Friendly name> pwwn <Fibre Channel WWPN>
mds(config-device-alias-db)# exit
mds(config)# end
There is an additional step required after defining the device aliases. You must also commit the changes to the device alias database, like this:
mds(config)# device-alias commit
This commits the changes to the device alias database and makes the device aliases active in the switch.
Once a device alias is created, it applies to that WWPN regardless of VSAN. This means that you only have to define a single device alias for any given WWPN, whereas with the fcalias command a different alias needed to be defined for each VSAN. All other things being equal (and they’re not equal, as you’ll see in a moment), that alone is worth switching to device aliases in my opinion.
Using device aliases also provides a couple other key benefits:
- Device aliases are automatically distributed to other Cisco-attached switches. For example, I defined the device aliases on a Cisco MDS 9134 that was attached to the Fibre Channel expansion port of a Cisco Nexus 5010 switch. The Nexus switch automatically picked up the device aliases. As best I can tell, this is controlled by the
device-alias distributeglobal configuration command (or its reverse, theno device-alias distribute, which would disable device alias distribution). - Once a device alias is defined for a WWPN, anytime the WWPN is displayed the device alias is also displayed. So in the output of various commands like
show flogi database,show fcns database, orshow zoneyou will see not only the WWPN, but also that WWPN’s associated device alias. - You can use the device alias as the destination with the
fcpingcommand.
All in all, I see a lot of value in using device aliases over simple Fibre Channel aliases. I’ll grant that some of this value is more readily apparent only in homogenous Cisco storage networks, but even in single-switch networks I personally would use device aliases.
To those who suggested I look at device aliases, I thank you! You’ve made my job easier.
As always, I welcome your feedback! Feel free to speak up in the comments with corrections, clarifications, or suggestions.
Tags: Cisco, FibreChannel, SAN, Storage
-
Hi Scott,
I was wondering if there was a way to track switchport info for a specific pwwn in a multiple MDS Switch environment. “show fcns database” doesn’t seem to map the switch/switchport info. I don’t seem to have access to “show alpa cache”.
Thanks,
Jeff -
As we are currently migrating to a pair of MDS9509′s, I’ve learned a lot of the commands hook into Cisco Fabric Services (CFS) which allows for the distribution of configuration data in a fabric.
Another cool ability of the switches is Dynamic Port VSAN Membership (DPVM) which allows you to assign VSAN membership to a device-alias and not a port. DPVM also uses CFS so you can take a connection move it anywhere in your fabric and it still retains connectivity to its VSAN.
-
Hi Guru,
Since we apply the device aliases instead of the the fcalias command,should the below CLI is the next step for the zoning?Kindly help me due to I’m still new with the cisco product..
switch(config)# zone name first-new-zone vsan XXX
switch(config-zone)# member device-alias stor-array-processor-a
switch(config-zone)# member device-alias server-hba
switch(config-zone)# exit
switch(config)#Thanks,
shidi -
Shidi, yes, that is correct. You use the “member device-alias” command to add device aliases to the zones instead of “member fcalias”.
I hope this helps!
-
ah thanks Scott…..you are awesome…
-
Hi Guru,
I have another concern when we create the device-alias zone.Should the below output correct ?
SELDSSW07# sh zone | include SELDCLU79B_SW701_B11
device-alias name SELDCLU79B_SW701_B11 vsan 3
pwwn 50:01:43:80:00:bf:9e:14 [SELDCLU79B_SW701_B11]P/s-I am manually replace the fcalias with the device-alias for my better understanding.Do correct me if my imagination is wrong since i’m still in a dumb category in Cisco SAN switch.Please…
Thanks,
Shidi -
Shidi, it looks like the output is correct, at least with regard to the “pwwn” statement. What you’ll see when using device aliases is that the MDS will show the pWWN followed by the device alias in brackets. So, it looks like your device alias is set correctly, based on the limited output above.
-
Hi,
What’s the defferent between fcalias and device-alias?
Best,
-
Matt, most of the differences are laid out in the article itself. For one, an fcalias is a per-VSAN setting, whereas a device alias is not. Refer back to the Cisco documentation for more details. If I get a chance, I’ll try to post something else about the differences between the two.
-
Hi Scott-
Wondering about the security implications of having Dev Aliases be seen by all VSANS.For example on a Cisco 9513 you can have a physical separation of VSANs…electronically.
So here is a scenerio:
The lawyers in a huge lawfirm have separate storage and SAN admins for courtroom and sensitive data and marketing and general office data on each VSAN. They bought the infrastructure using combined funding for infrastructure. They chose Cisco MDS do to it’s inherit physical separation of VSANs and for complying with regulations.VSAN112 (faba) and VSAN113 (fabb) contain sensitive courtroom data (say this is the lawyer’s super secrete secure stuff)
and
VSAN12(faba) and VSAN13(fabb) are hosts/systems that contain public websites, etc. (say this is the law office’s arrays and marketing things)I can see in this scenerio you would want to use FCalias over DevAliases for they are defined per-vsan.
Would it be a good idea to use Dev Aliases at this point? This could lead to someone accidentally putting one of these WWPN’s in the wrong vsan where as with fcalias’s things keep separate…. Or could you use a combination of both? And at that point would you want to do zoning using FCalias or Devalias?
Any thoughts? Thanks!
-
Brian, I personally don’t see any real concerns with the device alias being visible on multiple VSANs, since it’s “visible” only to the SAN administrator managing the MDS switch itself (or multiple MDS switches, depending on the SAN). Further, the presence of device aliases does not infer visibility across the fabric; you would still need to create zones and zonesets in order for initiators and targets to communicate. Finally, many hosts do not support F-port VSAN trunking, so they could only be part of one VSAN at a time anyway. Thus, the fact that a device alias exists for that host in another VSAN is a moot point since the host is in a different VSAN and can only communicate on a single VSAN at a time.
My 2 cents…
-
Awesome, thanks. The more I learn about device aliases the more I like the idea. Do you know of a tool that converts FC to Device? I figure that would be a very cool tool to have when migrating fabrics off of old non-Cisco hardware to Cisco.
This is good stuff… Would also like to hear opinions on single initiator -> single target vs. single initiator -> multi-target (same array) zoning as well. But that could be an entire blog post in itself. Both seem correct if done correctly (that is why I made the “same array” comment) but I am always going back and fourth of what would be the ‘best’ way. Especially in SANs that contain many Arrays and 100′s or 1000′s of hosts. Then again that is probably what multiple VSANs are for
Great blog…I refer to it a lot.
-
If you use device aliases make sure you enable the following if possible:
device-alias mode enhanced
Otherwise when it comes time to change the WWN of a device, eg due to HBA swap over, you will need to update the Device-Alias, and the associated zoning information.
In enhanced mode the WWN in the zone is subsituted for the device-alias. To change a HBA in a host you then only need to modify the WWN associated with a device-alias.
more info here:
http://www.cisco.com/en/US/docs/switches/datacenter/mds9000/sw/4_1/configuration/guides/fm_4_1/ddas.htmlCheers.
-
Brendon, is enhanced mode the default mode of operation for device aliases?
-
I don’t think so.
-
How does one properly chanage the wwpn of a device-alias? example an HBA fails and is replaced. I would like to just modify the definition. I’m found no way to do this in Fabric Manager. in cli I can do a “no device-alias hba-1″ than give it a new device alias but that does not appear to get reflected in my zones.
-
when you look at your zones are they built with device-alias members or wwn members? If you don’t have enhance device alias enabled then when you build your zones using the device-alias they get converted to use the wwn of the device-alias at the time.
-
Hello Scott,
I have MDS 9513 , I have zoned using pwwn for zoning, when I do show zoneset active it displays * [pWWN], is it normal? wheres in my other 9513 Switch it only displays Pwwn in show zoneset active
Thanks.
Ricky
-
Ricky, the “*” represents a pWWN that has logged into the fabric (as far as I know). If there is no asterisk then that pWWN hasn’t logged into the fabric.
-
Hi Scott,
I am currently setting up a pair of MDS 9148s. To save me from having to add new (virtual) WWNs everytime a new virtual HBA is added on the hardware nodes, I have added the Port-Channel group into the zone. Unfortunately, this is working for one fabric but not the other.
What would you use for setting this up so that the new WWNs are added into the zones automatically?
Thanks
-
Friends, I always have doubt… how would we differetiate the zones whether its created using device alias or pwwn? is there any clue to differentiate them?
Site Sponsors
21 comments
Comments feed for this article
Trackback link: http://blog.scottlowe.org/2010/12/08/using-device-aliases-on-a-cisco-mds/trackback/