DTP and VTP Domain [7:64892]
Is VTP dependent of DTP or is DTP dependent of VTP?. >From the following statement I think DTP can still form a trunk even if VTP domain is different on both switches. But I have read opposite statements. Unfortunatelly I can not test it now. Any thoughts? "The VTP protocol communicates between switches using an Ethernet destination multicast MAC address (01-00-0c-cc-cc-cc) and SNAP HDLC protocol type Ox2003. It does not work over non-trunk ports (VTP is a payload of ISL or 802.1Q), so messages cannot be sent until DTP has brought the trunk online." http://www.cisco.com/en/US/products/hw/switches/ps663/products_tech_note09186a0080094713.shtml Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=64892&t=64892 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
RE: DTP and VTP Domain [7:64892]
Found the answer on the same page. "In desirable mode, DTP packets transfer the VTP domain name (which must match for a negotiated trunk to come up), plus trunk configuration and admin status." Thanks Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=64893&t=64892 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
RE: DTP and VTP Domain [7:64892]
[EMAIL PROTECTED] wrote: > > Is VTP dependent of DTP or is DTP dependent of VTP?. > > From the following statement I think DTP can still form a trunk > even if VTP > domain is different on both switches. I doubt that DTP can form a trunk if the VTP domains are different, though Cisco's documentation is rather unclear about this: "To autonegotiate trunking, the interfaces must be in the same VTP domain. Use the trunk or nonegotiate keywords to force interfaces in different domains to trunk. For more information on VTP domains, see "Configuring VTP. Trunk negotiation is managed by the Dynamic Trunking Protocol (DTP). DTP supports autonegotiation of both ISL and 802.1Q trunks." The URL is: cisco.com/univercd/cc/td/doc/product/lan/cat6000/ios127xe/config/layer2.htm I think it's saying that DTP won't trunk if the VTP domains differ, but if you don't negotiate with DTP, and instead use the "trunk" or "nonegotiate" keywords, you can get the switches to trunk even if they are in different domains. (I've never heard of that, but that's what they seem to be saying.) I haven't ever sniffed a DTP frame. I have sniffed DISL frames and they have the VTP domain name in them. I bet DTP does too? And if they disagreed, I think the trunking would fail. > But I have read opposite > statements. > Unfortunatelly I can not test it now. Any thoughts? > >"The VTP protocol communicates between switches using an > Ethernet destination multicast >MAC address (01-00-0c-cc-cc-cc) and SNAP HDLC protocol type > Ox2003. Oh, isn't that awful they would call this HDLC. Ouch. The original HDLC protocol architecture didn't even have a method for defining the encapsulated protocol! That was added by many of the derivatives of HDLC, including PPP, Cisco HDLC, and Logical Link Control (LLC), used on LANs. Obviously this is a LAN, so they could have easily said LLC and/or SNAP instead of HDLC. VTP uses an LLC Source Service Access Point (SSAP) and Destination Service Access Point (DSAP) of 0xAA, meaning that the frame has an additional header, called a Subnetwork Access Protocol (SNAP) header. SNAP has a vendor code and two-byte protocol type. For VTP the protocol type is indeed 2003. DISL is 2004. I don't know for DTP? Anyone know? Could we guess 2005? A VTP frame is a difficult frame to sniff, but I have caught one in the wild. The ISL was stripped before the frame was given to my analyzer port. But here's what the rest of the VTP frame looks like: DLC: - DLC Header - DLC: DLC: Destination = Multicast 01000CCC DLC: Source = Station 00B06426795B DLC: 802.3 length = 284 DLC: LLC: - LLC Header - LLC: LLC: DSAP Address = AA, DSAP IG Bit = 00 (Individual Address) LLC: SSAP Address = AA, SSAP CR Bit = 00 (Command) LLC: Unnumbered frame: UI LLC: SNAP: - SNAP Header - SNAP: SNAP: Vendor ID = Cisco1 SNAP: Type = 2003 (VTP) SNAP: VTP: - Cisco Virtual Trunk Protocol (VTP) Packet - VTP: VTP: Version = 1 VTP: Message type = 0x02 (Subset-Advert) VTP: Sequence number = 1 VTP: Management Domain Name length= 3 VTP: Management Domain Name = "Lab" VTP: Number of Padding bytes = 29 VTP: Configuration revision number= 0x0002 VTP: VTP: VLAN Information Field # 1: VTP: VLAN information field length= 28 VTP: VLAN Status = 00 (Operational) VTP: VLAN type= 1 (Ethernet) VTP: Length of VLAN name = 7 VTP: ISL VLAN-id = 1 VTP: MTU size = 1500 VTP: 802.10 SAID field= 11 VTP: VLAN Name= "default" VTP: # padding bytes in VLAN Name = 1 VTP: Reserved 8 bytes VTP: VTP: VLAN Information Field # 2: VTP: VLAN information field length= 24 VTP: VLAN Status = 00 (Operational) VTP: VLAN type= 1 (Ethernet) VTP: Length of VLAN name = 11 VTP: ISL VLAN-id = 10 VTP: MTU size = 1500 VTP: 802.10 SAID field= 100010 VTP: VLAN Name= "Engineering" VTP: # padding bytes in VLAN Name = 1 VTP: VTP: VLAN Information Field # 3: VTP: VLAN information field length= 24 VTP: VLAN Status = 00 (Operational) VTP: VLAN type= 1 (Ethernet) VTP: Length of VLAN name = 10 VTP: ISL VLAN-id = 50 VTP: MTU size = 1500 VTP: 802.10 SAID field= 100050 VTP: VLAN Name= "Accountin
RE: DTP and VTP Domain [7:64892]
DTP uses protocol type 2004 too, just like DISL. I guess it's just an update to DISL for use with 802.1Q rather than ISL? And, I figured out why you might want to tell DTP not to autonegotiate or be desirable and why in that case no VTP domain name is exchanged and the VTP domain names don't have to match. The main reason is that the other end might not be Cisco and might not care about VTP anyway. Does that make sense? Priscilla Priscilla Oppenheimer wrote: > > [EMAIL PROTECTED] wrote: > > > > Is VTP dependent of DTP or is DTP dependent of VTP?. > > > > From the following statement I think DTP can still form a > trunk > > even if VTP > > domain is different on both switches. > > I doubt that DTP can form a trunk if the VTP domains are > different, though Cisco's documentation is rather unclear about > this: > > "To autonegotiate trunking, the interfaces must be in the same > VTP domain. Use the trunk or nonegotiate keywords to force > interfaces in different domains to trunk. For more information > on VTP domains, see "Configuring VTP. Trunk negotiation is > managed by the Dynamic Trunking Protocol (DTP). DTP supports > autonegotiation of both ISL and 802.1Q trunks." > > The URL is: > > cisco.com/univercd/cc/td/doc/product/lan/cat6000/ios127xe/config/layer2.htm > > I think it's saying that DTP won't trunk if the VTP domains > differ, but if you don't negotiate with DTP, and instead use > the "trunk" or "nonegotiate" keywords, you can get the switches > to trunk even if they are in different domains. (I've never > heard of that, but that's what they seem to be saying.) > > I haven't ever sniffed a DTP frame. I have sniffed DISL frames > and they have the VTP domain name in them. I bet DTP does too? > And if they disagreed, I think the trunking would fail. > > > But I have read opposite > > statements. > > Unfortunatelly I can not test it now. Any thoughts? > > > >"The VTP protocol communicates between switches using an > > Ethernet destination multicast > >MAC address (01-00-0c-cc-cc-cc) and SNAP HDLC protocol type > > Ox2003. > > Oh, isn't that awful they would call this HDLC. Ouch. The > original HDLC protocol architecture didn't even have a method > for defining the encapsulated protocol! That was added by many > of the derivatives of HDLC, including PPP, Cisco HDLC, and > Logical Link Control (LLC), used on LANs. > > Obviously this is a LAN, so they could have easily said LLC > and/or SNAP instead of HDLC. VTP uses an LLC Source Service > Access Point (SSAP) and Destination Service Access Point (DSAP) > of 0xAA, meaning that the frame has an additional header, > called a Subnetwork Access Protocol (SNAP) header. SNAP has a > vendor code and two-byte protocol type. For VTP the protocol > type is indeed 2003. DISL is 2004. I don't know for DTP? Anyone > know? Could we guess 2005? > > A VTP frame is a difficult frame to sniff, but I have caught > one in the wild. The ISL was stripped before the frame was > given to my analyzer port. But here's what the rest of the VTP > frame looks like: > > DLC: - DLC Header - > DLC: > DLC: Destination = Multicast 01000CCC > DLC: Source = Station 00B06426795B > DLC: 802.3 length = 284 > DLC: > LLC: - LLC Header - > LLC: > LLC: DSAP Address = AA, DSAP IG Bit = 00 (Individual > Address) > LLC: SSAP Address = AA, SSAP CR Bit = 00 (Command) > LLC: Unnumbered frame: UI > LLC: > SNAP: - SNAP Header - > SNAP: > SNAP: Vendor ID = Cisco1 > SNAP: Type = 2003 (VTP) > SNAP: > VTP: - Cisco Virtual Trunk Protocol (VTP) Packet - > VTP: > VTP: Version = 1 > VTP: Message type = 0x02 > (Subset-Advert) > VTP: Sequence number = 1 > VTP: Management Domain Name length= 3 > VTP: Management Domain Name = "Lab" > VTP: Number of Padding bytes = 29 > VTP: Configuration revision number= 0x0002 > VTP: > VTP: VLAN Information Field # 1: > VTP: VLAN information field length= 28 > VTP: VLAN Status = 00 (Operational) > VTP: VLAN type= 1 (Ethernet) > VTP: Length of VLAN name = 7 > VTP: ISL VLAN-id = 1 > VTP: MTU size = 1500 > VTP: 802.10 SAID field= 11 > VTP: VLAN Name= "default" > VTP: # padding bytes in VLAN Name = 1 > VTP: Reserved 8 bytes > VTP: > VTP: VLAN Information Field # 2: > VTP: VLAN information field length= 24 > VTP: VLAN Status = 00 (Operational) > VTP: VLAN type= 1 (Ethernet) > VTP: Length of VLAN name = 11 > VTP: ISL VLAN-id = 10 >
Re: DTP and VTP Domain [7:64892]
Priscilla Oppenheimer wrote: > > DTP uses protocol type 2004 too, just like DISL. I guess it's just an update > to DISL for use with 802.1Q rather than ISL? > Yes. Step 1: negotiate whether to trunk. Step 2: if the result is yes, then negotiate which flavor. If both are indifferent, favor ISL. > And, I figured out why you might want to tell DTP not to autonegotiate or be > desirable and why in that case no VTP domain name is exchanged and the VTP > domain names don't have to match. The main reason is that the other end > might not be Cisco and might not care about VTP anyway. Does that make sense? > Or the other switch is a Cisco one that doesn't speak DTP. The 2900/3500XLs and the 2950 didn't speak DTP until recently. Skipping the DTP negotiation with a device that isn't capable eliminates one source of delay before STP is handed the port. I was told by someone in Cisco that the original reason for "nonegotiate" was that the early ISL NIC drivers in servers didn't gracefully ignore the DTP multicast, but crashed the server! - Marty Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=64985&t=64892 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: DTP and VTP Domain [7:64892]
As long as the native VLAN is the same on both ends so that the ends of the prospective trunk link can communicate, DTP will be able to form the trunk. The VTP domain is irrelevant. All DTP needs is layer 2 connectivity and the desire (on both ends) to trunk. :-) In fact, one of the requirements for a VTP domain to exist is that trunking must be enabled between the switches. In light of this, I would say that VTP is dependent on DTP or DISL but DTP and DISL are NOT dependent on VTP. Hope this helps, Karen *** REPLY SEPARATOR *** On 3/10/2003 at 12:30 PM [EMAIL PROTECTED] wrote: >Is VTP dependent of DTP or is DTP dependent of VTP?. > >From the following statement I think DTP can still form a trunk even if VTP >domain is different on both switches. But I have read opposite statements. >Unfortunatelly I can not test it now. Any thoughts? > > "The VTP protocol communicates between switches using an Ethernet >destination multicast > MAC address (01-00-0c-cc-cc-cc) and SNAP HDLC protocol type Ox2003. > It does not work over non-trunk ports (VTP is a payload of ISL or >802.1Q), > so messages cannot be sent until DTP has brought the trunk online." > > >http://www.cisco.com/en/US/products/hw/switches/ps663/products_tech_note09186a0080094713.shtml Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=64996&t=64892 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: DTP and VTP Domain [7:64892]
The link that follows also says VTP domain is one field on DISL and DTP. If the switches do not agree on the VTP domain and DTP (or DISL) are set to 'negotiate', the trunk will not come up. www.it.rit.edu/~netsyslb/icsa515/ ExtraResources/VTP.pdf Thanks to all Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=65044&t=64892 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: DTP and VTP Domain [7:64892]
Hi Karen, Are you back in the U.S.? Welcome back, if yes! I consider you a guru of campus networking technologies from the answers you give on GroupStudy. Alaerte and I have noticed that with DTP set to negotiate, the VTP domain name is exchanged and if it doesn't match the trunk doesn't form. Have you heard of that? The workaround is to use the trunk or nonegotiate keywords to force interfaces in different domains to trunk. Thanks, Priscilla Karen E Young wrote: > > As long as the native VLAN is the same on both ends so that the > ends of the prospective trunk link can communicate, DTP will be > able to form the trunk. The VTP domain is irrelevant. All DTP > needs is layer 2 connectivity and the desire (on both ends) to > trunk. :-) > > In fact, one of the requirements for a VTP domain to exist is > that trunking must be enabled between the switches. > > In light of this, I would say that VTP is dependent on DTP or > DISL but DTP and DISL are NOT dependent on VTP. > > Hope this helps, > Karen > > *** REPLY SEPARATOR *** > > On 3/10/2003 at 12:30 PM [EMAIL PROTECTED] wrote: > > >Is VTP dependent of DTP or is DTP dependent of VTP?. > > > >From the following statement I think DTP can still form a > trunk even if VTP > >domain is different on both switches. But I have read opposite > statements. > >Unfortunatelly I can not test it now. Any thoughts? > > > > "The VTP protocol communicates between switches using an > Ethernet > >destination multicast > > MAC address (01-00-0c-cc-cc-cc) and SNAP HDLC protocol type > Ox2003. > > It does not work over non-trunk ports (VTP is a payload of > ISL or > >802.1Q), > > so messages cannot be sent until DTP has brought the trunk > online." > > > > > >http://www.cisco.com/en/US/products/hw/switches/ps663/products_tech_note09186a0080094713.shtml > > Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=65112&t=64892 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: DTP and VTP Domain [7:64892]
Yes, I'm back. For now. I may be heading back to Amsterdam next month though. I hate looonnnggg flights. Boring. I had heard of the "negotiate" thing. However, I've had problems with that in the past. Kind of like using "auto" on a 10/100 port. Doesn't always work. Even when the config is perfect and both ends are in the same domain it may fail to establish the trunk, especially between a router and a switch. I usually end up idiotproofing it by forcing it to trunk. Unfortunately, that would have its own problems if trunking happens to go down anyway. Keeps you from accessing the switch remotely and you have to be connected either to a console poret or to a port configured with the same VLAN as the switch's management interface. Good thing that hasn't ever happened to me (so far). :-) *** REPLY SEPARATOR *** On 3/12/2003 at 12:00 AM Priscilla Oppenheimer wrote: >Hi Karen, > >Are you back in the U.S.? Welcome back, if yes! I consider you a guru of >campus networking technologies from the answers you give on GroupStudy. > >Alaerte and I have noticed that with DTP set to negotiate, the VTP domain >name is exchanged and if it doesn't match the trunk doesn't form. Have you >heard of that? > >The workaround is to use the trunk or nonegotiate keywords to force >interfaces in different domains to trunk. > >Thanks, > >Priscilla > > >Karen E Young wrote: >> >> As long as the native VLAN is the same on both ends so that the >> ends of the prospective trunk link can communicate, DTP will be >> able to form the trunk. The VTP domain is irrelevant. All DTP >> needs is layer 2 connectivity and the desire (on both ends) to >> trunk. :-) >> >> In fact, one of the requirements for a VTP domain to exist is >> that trunking must be enabled between the switches. >> >> In light of this, I would say that VTP is dependent on DTP or >> DISL but DTP and DISL are NOT dependent on VTP. >> >> Hope this helps, >> Karen >> >> *** REPLY SEPARATOR *** >> >> On 3/10/2003 at 12:30 PM [EMAIL PROTECTED] wrote: >> >> >Is VTP dependent of DTP or is DTP dependent of VTP?. >> > >> >From the following statement I think DTP can still form a >> trunk even if VTP >> >domain is different on both switches. But I have read opposite >> statements. >> >Unfortunatelly I can not test it now. Any thoughts? >> > >> > "The VTP protocol communicates between switches using an >> Ethernet >> >destination multicast >> > MAC address (01-00-0c-cc-cc-cc) and SNAP HDLC protocol type >> Ox2003. >> > It does not work over non-trunk ports (VTP is a payload of >> ISL or >> >802.1Q), >> > so messages cannot be sent until DTP has brought the trunk >> online." >> > >> > >> >>http://www.cisco.com/en/US/products/hw/switches/ps663/products_tech_note09186a0080094713.shtml Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=65125&t=64892 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: DTP and VTP Domain [7:64892]
I learned this lesson the hard way a few days ago. Had to drive out to the remote site and change the VTP name back so the trunk would come back up. After consulting CCO (which I probably should have done in the first place) I set all the trunks to nonegotiate on switches I planned to change the VTP domain name. Then I changed the VTP domain names. My users were happier the second time around. Is there a benefit to DTP? >>> "Priscilla Oppenheimer" 03/11/03 04:00PM >>> Hi Karen, Are you back in the U.S.? Welcome back, if yes! I consider you a guru of campus networking technologies from the answers you give on GroupStudy. Alaerte and I have noticed that with DTP set to negotiate, the VTP domain name is exchanged and if it doesn't match the trunk doesn't form. Have you heard of that? The workaround is to use the trunk or nonegotiate keywords to force interfaces in different domains to trunk. Thanks, Priscilla Karen E Young wrote: > > As long as the native VLAN is the same on both ends so that the > ends of the prospective trunk link can communicate, DTP will be > able to form the trunk. The VTP domain is irrelevant. All DTP > needs is layer 2 connectivity and the desire (on both ends) to > trunk. :-) > > In fact, one of the requirements for a VTP domain to exist is > that trunking must be enabled between the switches. > > In light of this, I would say that VTP is dependent on DTP or > DISL but DTP and DISL are NOT dependent on VTP. > > Hope this helps, > Karen > > *** REPLY SEPARATOR *** > > On 3/10/2003 at 12:30 PM [EMAIL PROTECTED] wrote: > > >Is VTP dependent of DTP or is DTP dependent of VTP?. > > > >From the following statement I think DTP can still form a > trunk even if VTP > >domain is different on both switches. But I have read opposite > statements. > >Unfortunatelly I can not test it now. Any thoughts? > > > > "The VTP protocol communicates between switches using an > Ethernet > >destination multicast > > MAC address (01-00-0c-cc-cc-cc) and SNAP HDLC protocol type > Ox2003. > > It does not work over non-trunk ports (VTP is a payload of > ISL or > >802.1Q), > > so messages cannot be sent until DTP has brought the trunk > online." > > > > > >http://www.cisco.com/en/US/products/hw/switches/ps663/products_tech_note09186a0080094713.shtml Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=65124&t=64892 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
RE: DTP and VTP Domain [7:64892]
*** REPLY SEPARATOR *** On 3/12/2003 at 12:00 AM Priscilla Oppenheimer wrote: >Hi Karen, > >Are you back in the U.S.? Welcome back, if yes! I consider you a guru of >campus networking technologies from the answers you give on GroupStudy. > Yes, that's absolutely true. When I hear about her name, it's almost synonymous with Kennedy Clark. I've enjoyed reading her posts since I "met" her on this list about 3 years ago. Best wishes to a great professional. Elmer Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=65159&t=64892 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
