VTP domain

Mikdilly

Does the revision number matter when you change the vtp domain name on a switch? As in, does the domain name propagate to all other trunked switches in client or server mode if the revision number on the switch used to change the name has a revision number lower than the rest of the switches?

elvant

The link below will help you to understand vtp problem (someone post this link before)

http://www.cisco.com/warp/public/473/vtp_flash/

rjbarlow

Mikdilly wrote:

Does the revision number matter when you change the vtp domain name on a switch? As in, does the domain name propagate to all other trunked switches in client or server mode if the revision number on the switch used to change the name has a revision number lower than the rest of the switches?

Mmh, maybe I understood well your question; my answer is:
switches thsat do not share the same VTP domain name, do not advertise from each other VLAN information.

Netstudent

In that flash tutorial that weng posted, it states that you can configure the VTP domain name on the server, and that domain name will propagate the trunk and automatically configure the client with the new domain name via Summary advertisement and subset advertisement frames. Now I see this as bringing a client switch from NULL to the new domain name. I did not know this was an option. Can anyone verify that?

Also what if the client is not NULL and is already configured with a domain name. Then when that domain name is changed on the server, the Rev.# increments. So in this case, will the clients still update their Domain name?

This has sparked some questions for me too.

Guess I'll have to lab this one up tonight.

elvant

Switch will dynamically change its domain (when receive the ads) only if the domain name is NULL, if the domain is something other than NULL, it will not change its domain name either in server or in client mode.

Mikdilly

I've read that by default catalyst 3550/3560 switches are a member of a domain called NULL and will not propagate vlan information from one switch to another, but once the domain is changed the vtp domain name is propagated to other switches. So would think that if all switches had an existing domain name other than NULL and one of those switches had it's domain name changed then that domain name would be propagated to all other trunked switches.

elvant

When a switch received a ads from neighboring switch, it will first look at the domain name. If the domain is different than its own, it will ignore and discard the ads. (except the NULL case)

taken from the flash's example, you have 2 switches A and B connected with the same domain name ( vlans info is syn ), then you add a switch C with a different domain name between A and B. Becoz a switch will ignore ads from a neighboring switch with a different domain name. Any changes in A will not syn to B becoz the ads send by A is discard by C and unable to reach B.
rather than the C will dynamically change its domain name identical to A and B or vice versa.

If a domain name can be dynamically changed (again, except NULL), then eventually all the domain name in a LAN will only have a domain name, which is not true.

Mikdilly

wengyau wrote:

When a switch received a ads from neighboring switch, it will first look at the domain name. If the domain is different than its own, it will ignore and discard the ads. (except the NULL case)

taken from the flash's example, you have 2 switches A and B connected with the same domain name ( vlans info is syn ), then you add a switch C with a different domain name between A and B. Becoz a switch will ignore ads from a neighboring switch with a different domain name. Any changes in A will not syn to B becoz the ads send by A is discard by C and unable to reach B.
rather than the C will dynamically change its domain name identical to A and B or vice versa.

If a domain name can be dynamically changed (again, except NULL), then eventually all the domain name in a LAN will only have a domain name, which is not true.

Thanks

Netstudent

wengyau wrote:

When a switch received a ads from neighboring switch, it will first look at the domain name. If the domain is different than its own, it will ignore and discard the ads. (except the NULL case)

taken from the flash's example, you have 2 switches A and B connected with the same domain name ( vlans info is syn ), then you add a switch C with a different domain name between A and B. Becoz a switch will ignore ads from a neighboring switch with a different domain name. Any changes in A will not syn to B becoz the ads send by A is discard by C and unable to reach B.
rather than the C will dynamically change its domain name identical to A and B or vice versa.

If a domain name can be dynamically changed (again, except NULL), then eventually all the domain name in a LAN will only have a domain name, which is not true.

Good Point. Ya I could see it dynamically going from NULL to some value, even though I did not know that, but dynamically going from a value to another value, didn't sound right. Had to ask though. Thanks Weng.

networker050184

Yes weng is right. If you would like to see it just plugg up two switches with no domain names. If you change one and telnet to the other it will already have the new domain name.

mikearama

I went one step further...

My lab has 3 2950's. I changed all domain names to NULL to clear everything. Then I gave one a domain name (CCNP). As networker said, all three were now Servers in CCNP... so I had to change two into clients.

Next, I changed the name of the domain on the Server to something new (CCSP). Both Clients stayed with the CCNP name... meaning I now had a vtp domain without a Server. Interesting.

Lastly, after making one of the Clients in CCNP into a Server, I took the new standalone CCSP Server from the network... played with it until it had a far higher revision, and added it back. Sure enough, no change to the CCNP domain at all. So then I took it off the network, added more vlans, and change the domain name to CCNP and added it back. Instantly (well, as quick as I could telnet to the other two) they had the information from the new Server.

This stuff is right out of the BCMSN material. Well, mostly. Very neat stuff.

Netstudent

COOL! Ya I was going to lab it up myself, but never got around to it.