01-04-2014 02:51 AM - edited 03-07-2019 05:22 PM
1. What is the code for an "Summary Advertisement" whereas it is 0x03 for 'Advertisement Request'
2. Can someome please expain about the followers field in a 'Summary Advertisement' ? What does it holds?
I understood that inthis way:It tells the receiving switch that after this message you're going to receive summary advertisements. I'm i correct? If yes what value does it put's in that field.
3. If the switches exchanged the 'Summary Advertisement' if they found that the configuration revision value is same, even then will they sendout subset advertisement?
Regards,
Chandu
Solved! Go to Solution.
01-04-2014 03:26 AM
Hi Chandu,
the VTP message codes are:
0x01: Summary Advertisement
0x02: Subset Advertisement
0x03: Advertisement Request
0x04: Join (=> Pruning)
0x05: ? (VTPv3, I've captured such PDUs but couldn't find out what they are so far)
The Summary Advertisements are send in 5-minute intervals just to make sure that VLAN information keeps synchronized within the domain (e.g. for new devices). The followers field is set to zero in this case.
If a change is made in the VLAN configuration and the Configuration Revision increases, a Summary Advertisement is send with the followers fields set to one, which means that a Subset Advertisement will follow (containing the detail information), so that new information can will be populated within the domain immediately after the change.
You can see this sequence in the Wireshark capture file I've attached.
I don't know if PT supports debug commands, a "debug sw-vlan vtp events" provides some interesting output as well:
VTP LOG RUNTIME: Summary packet received, domain =VTPTEST , rev = 8, followers = 0, length 77, trunk Gi0/1
VTP LOG RUNTIME: Summary packet rev 8 equal to domain VTPTEST rev 8
VTP LOG RUNTIME: Summary packet rev 9 greater than domain VTPTEST rev 8
(...)
HTH
Rolf
01-04-2014 03:26 AM
Hi Chandu,
the VTP message codes are:
0x01: Summary Advertisement
0x02: Subset Advertisement
0x03: Advertisement Request
0x04: Join (=> Pruning)
0x05: ? (VTPv3, I've captured such PDUs but couldn't find out what they are so far)
The Summary Advertisements are send in 5-minute intervals just to make sure that VLAN information keeps synchronized within the domain (e.g. for new devices). The followers field is set to zero in this case.
If a change is made in the VLAN configuration and the Configuration Revision increases, a Summary Advertisement is send with the followers fields set to one, which means that a Subset Advertisement will follow (containing the detail information), so that new information can will be populated within the domain immediately after the change.
You can see this sequence in the Wireshark capture file I've attached.
I don't know if PT supports debug commands, a "debug sw-vlan vtp events" provides some interesting output as well:
VTP LOG RUNTIME: Summary packet received, domain =VTPTEST , rev = 8, followers = 0, length 77, trunk Gi0/1
VTP LOG RUNTIME: Summary packet rev 8 equal to domain VTPTEST rev 8
VTP LOG RUNTIME: Summary packet rev 9 greater than domain VTPTEST rev 8
(...)
HTH
Rolf
01-06-2014 10:43 PM
Thanks a lot Rolf.
And PT is supporting debug for vtp events, it was very helpful.
So the follower field is just to indicate if there are any subset advertiesements that are going to be transmitted or not. If yes then the count of the subset advertisement messages will be placed in the followers field.
Thanks again for the wireshark captures.
Regards,
Chandu
01-07-2014 05:25 AM
Chandu, you're welcome. Thanks for the feedback.
So the follower field is just to indicate if there are any subset advertiesements that are going to be transmitted or not. If yes then the count of the subset advertisement messages will be placed in the followers field.
That's actually a more precise description than what I wrote.
You're correct: When the vlan information cannot be storred in a single frame, more than one Subset Advertisement has to be sent and the number is indicated in the followers field:
VTP LOG RUNTIME: Summary packet received, domain = VTPTEST, rev = 1, followers = 2, length 77, trunk Fa0/0
VTP LOG RUNTIME: Summary packet rev 1 greater than domain VTPTEST rev 0
VTP LOG RUNTIME: Subset packet received, domain = VTPTEST, rev = 1, seq = 1, length = 1468
VTP LOG RUNTIME: Subset packet received, domain = VTPTEST, rev = 1, seq = 2, length = 1324
Cheers,
Rolf
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