How to update VTP client safely

[q-le]

Hi All,

We have in production a VTP server Nexus 7k  and say 30 xVTP clients Cat3550 switches all behaving correctly except one client.

ie it got only say 195 vlans instead of 200 vlans in the server and other clients and it has MD5 number digest different from others

I find a couple of ways from Google such as:

1)

Change the domain of the client and rechange it back to the same domain this should reset the VTP counter

and now the client will get the VLANS from the VLAN server

or

2)

change the switch that needs the update to Transparent mode which resets

the counter to Zero and then put it back into client mode or server mode.

the Client switch is in production and I am worry that it will cause issues.

Any help is very much appreciated.

Thanks

Leq

[glen.grant]

  Does the nexus indicate any kind of problem with that particular vpc.  Nexus does a lot of compatability checking on a number of parameters when you are using a VPC.   Is there 2 uplinks to 2 different Nexus boxes ?   Are you using LACP to form the channels ?  Also check this ,  something I didn't know until I looked it up on nexus .  don't see it allowed on either side. kind of contrary to what they usually tell you where they do not want vlaN 1 propagated all over . Notice above where you show the one that works has vlan 1 in the trunk and the one that does not does not have vlan 1 in the trunk . If none of these work I'm out of ideas. 

Note

---

VLAN  1 is required on all trunk ports used for switch interconnects if VTP  is supported in the network. Disabling VLAN 1 from any of these ports  prevents VTP from functioning properly.

---

[wpalumbo06]

One thing that looks odd from your output is the date on the client switch - several months off from the VTP server.  Not real sure how critical that is but I have seen plenty of weird issues when NTP wasn't working correctly - usually when there is some kind of replication like VTP.  Are the other client switches working with their time set like the problem switch?

Bill

[paul driver]

Hello

Try renaming the vlan.dat file on the switch and letting it creeate another

Client vtp switch:

dir flash:vlan.dat

rename flash:vlan.dat vlan.datOLD

Server vtp switch

Create dummy vlan

vlan xx

exit

Client vtp switch

sh vlan brief

:

res

Paul

Please don't forget to rate any posts that have been helpful.

Thanks.

[q-le]

Hi Paul,

Tried rename VLAN.dat as suggested but make no different.

Please see output from a working switch:

LAS-SDESK#sh vtp status

VTP Version                     : running VTP2

Configuration Revision          : 254

Maximum VLANs supported locally : 1005

Number of existing VLANs        : 128

VTP Operating Mode              : Client

VTP Domain Name                 : QNC

VTP Pruning Mode                : Enabled

VTP V2 Mode                     : Enabled

VTP Traps Generation            : Enabled

MD5 digest                      : 0xE1 0x9B 0xD1 0xD1 0x82 0x1F 0x3B 0xE2

Configuration last modified by 172.17.254.251 at 2-13-14 13:11:12

The IP address 172.17.254.251 is the loopback address of the Server Nexus

Output from a non-working client:

LAS-WFS#sh vtp status

VTP Version                     : running VTP2

Configuration Revision          : 0

Maximum VLANs supported locally : 1005

Number of existing VLANs        : 123

VTP Operating Mode              : Client

VTP Domain Name                 : QNC

VTP Pruning Mode                : Enabled

VTP V2 Mode                     : Enabled

VTP Traps Generation            : Enabled

MD5 digest                      : 0x1F 0xC4 0x32 0xC1 0x02 0x2C 0x2F 0x4B

Configuration last modified by 172.18.100.1 at 7-21-13 23:11:39

The IP address 172.18.100.1 is the VLAN 100  address of the Core Nexus another IP address.

so HOW do we tell the Client to point to the Correct Server IP address which is 172.17.254.251

Thanks

Leq

[glen.grant · Accepted solution]

     Did you add vlan 1 to the allowed vlans on both sides of the link , it is a requirement when using nexus in a vtp environment for it to work correctly.I would add it to both sides and bounce the link.See previous  post.

[paul driver · Accepted solution]

Hello Glen,

Having not had  little exposure to nexus so wasnt aware of this vtp requirment - Nice to know - Cheers!

Configuring VTP

You can configure VTP on Cisco NX-OS devices.

Note	VLAN 1 is required on all trunk ports used for switch  interconnects if VTP is supported in the network. Disabling VLAN 1 from  any of these ports prevents VTP from functioning properly.

res

Paul

Please don't forget to rate any posts that have been helpful.

Thanks.

[q-le]

Hi Glen,

You are star !!!!

Thank you so much - it works perfectly the minutues I add VLAN 1 in the Client.

All VTP are flowing again.

Thanks so much all - very much appreciated.

Leq

[Kevin Dorrell]

That is really interesting Glen. On Catalysts, I have often trimmed VLAN 1 off the trunks (and also my "dummy" native VLAN) with no ill effect on the VTP. But I have never so on the Nexus. So thanks, you have probably saved me from problems in the future.

It reminds me of the old CatOS switches, which if the native VLAN got pruned from a trunk then the control protocols would stop working.

Kevin Dorrell
Luxembourg



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