RE: Token Ring Routing Control Field
What a great site! Thanks for the URL. Priscilla At 04:29 PM 3/22/01, COULOMBE, TROY wrote: >http://www.techfest.com/networking/lan/token.htm > >HTH, > >TroyC > >-Original Message- >From: John Neiberger [mailto:[EMAIL PROTECTED]] >Sent: Thursday, March 22, 2001 3:26 PM >To: [EMAIL PROTECTED] >Cc: [EMAIL PROTECTED] >Subject: Re: Token Ring Routing Control Field > > >True. So what does the third bit (from the left) do? I didn't see any >mention of the third bit doing anything so I assumed it was zero, hence >my confusion. If it's not doing anything, why would it be a one >sometimes and a zero other times? > >I've read a token ring FAQ also and still haven't found a mention of >what that bit is for. > >Thanks, >John > > >>> "John Mistichelli" <[EMAIL PROTECTED]> 3/22/01 4:17:59 PM >>> > >"A" also starts with 10 > >8 = 1000 > >A = 1010 > >B = 1011 > > > > > John Neiberger <[EMAIL PROTECTED]> wrote: >Okay, now I'm confused by something in the Sybex CCIE study guide in >the >token ring chapter. It says that if the first two bits of the routing >control field are 10 the frame is an all-routes explorer. If the first >two bits are 11 then it's a single-route explorer. > >In all of their examples, when they convert the first nibble to hex >they use A for allroutes explorer and C to indicate single route >explorer. I understand "C" because 1100 = C, but 1000 = 8, not A. >What's the deal? Am I losing my mind or is the book wrong? I've >noticed the book has been wrong in several other places but this is a >new topic for me. > > From what I can tell, a RIF that starts with 8 is an all-routes >explorer. If it starts with C it is a single-route explorer. If it >starts with zero it is a nonexplorer frame. Is this correct? > >Thanks, >John > >_ >FAQ, list archives, and subscription info: >http://www.groupstudy.com/list/cisco.html >Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] > > > > >John Mistichelli >CCSI #2, CCNP, CCDA, MCSE, CNE >[EMAIL PROTECTED] > > >- >Do You Yahoo!? >Yahoo! Mail Personal Address - Get email at your own domain with Yahoo! >Mail. > >_ >FAQ, list archives, and subscription info: >http://www.groupstudy.com/list/cisco.html >Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] > >_ >FAQ, list archives, and subscription info: >http://www.groupstudy.com/list/cisco.html >Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] Priscilla Oppenheimer http://www.priscilla.com _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
RE: Token Ring Routing Control Field
http://www.techfest.com/networking/lan/token.htm HTH, TroyC -Original Message- From: John Neiberger [mailto:[EMAIL PROTECTED]] Sent: Thursday, March 22, 2001 3:26 PM To: [EMAIL PROTECTED] Cc: [EMAIL PROTECTED] Subject: Re: Token Ring Routing Control Field True. So what does the third bit (from the left) do? I didn't see any mention of the third bit doing anything so I assumed it was zero, hence my confusion. If it's not doing anything, why would it be a one sometimes and a zero other times? I've read a token ring FAQ also and still haven't found a mention of what that bit is for. Thanks, John >>> "John Mistichelli" <[EMAIL PROTECTED]> 3/22/01 4:17:59 PM >>> "A" also starts with 10 8 = 1000 A = 1010 B = 1011 John Neiberger <[EMAIL PROTECTED]> wrote: Okay, now I'm confused by something in the Sybex CCIE study guide in the token ring chapter. It says that if the first two bits of the routing control field are 10 the frame is an all-routes explorer. If the first two bits are 11 then it's a single-route explorer. In all of their examples, when they convert the first nibble to hex they use A for allroutes explorer and C to indicate single route explorer. I understand "C" because 1100 = C, but 1000 = 8, not A. What's the deal? Am I losing my mind or is the book wrong? I've noticed the book has been wrong in several other places but this is a new topic for me. >From what I can tell, a RIF that starts with 8 is an all-routes explorer. If it starts with C it is a single-route explorer. If it starts with zero it is a nonexplorer frame. Is this correct? Thanks, John _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] John Mistichelli CCSI #2, CCNP, CCDA, MCSE, CNE [EMAIL PROTECTED] - Do You Yahoo!? Yahoo! Mail Personal Address - Get email at your own domain with Yahoo! Mail. _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: Token Ring Routing Control Field
True. So what does the third bit (from the left) do? I didn't see any mention of the third bit doing anything so I assumed it was zero, hence my confusion. If it's not doing anything, why would it be a one sometimes and a zero other times? I've read a token ring FAQ also and still haven't found a mention of what that bit is for. Thanks, John >>> "John Mistichelli" <[EMAIL PROTECTED]> 3/22/01 4:17:59 PM >>> "A" also starts with 10 8 = 1000 A = 1010 B = 1011 John Neiberger <[EMAIL PROTECTED]> wrote: Okay, now I'm confused by something in the Sybex CCIE study guide in the token ring chapter. It says that if the first two bits of the routing control field are 10 the frame is an all-routes explorer. If the first two bits are 11 then it's a single-route explorer. In all of their examples, when they convert the first nibble to hex they use A for allroutes explorer and C to indicate single route explorer. I understand "C" because 1100 = C, but 1000 = 8, not A. What's the deal? Am I losing my mind or is the book wrong? I've noticed the book has been wrong in several other places but this is a new topic for me. >From what I can tell, a RIF that starts with 8 is an all-routes explorer. If it starts with C it is a single-route explorer. If it starts with zero it is a nonexplorer frame. Is this correct? Thanks, John _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] John Mistichelli CCSI #2, CCNP, CCDA, MCSE, CNE [EMAIL PROTECTED] - Do You Yahoo!? Yahoo! Mail Personal Address - Get email at your own domain with Yahoo! Mail. _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: Token Ring Routing Control Field
There is confusion on this issue because there's more than one standard. IBM "standardized" source-route bridging in their Token Ring Architectural Reference Guide many years ago. The IEEE had nothing to do with this weirdness until the early 1990s when they standardized Source-Route Transparent bridging in Annex C of IEEE 802.1D. (Don't believe the books that claim it is in 802.5.) The IEEE document says this, where an X bit is undefined (can have any value): 0XX = specific route (non-broadcast) 10X = all routes explorer 11X = spanning-tree explorer IBM didn't originally define a spanning-tree explorer, but they did define the following: 110 = single-route broadcast, all routes broadcast return 111 = single-route broadcast, non-broadcast return Without a spanning tree, administrators had to manually configure redundant bridges to make sure a 11x explorer only took one path. Later IBM introduced automatic and spanning-tree features. Anyway, to make a long story short, C or A would be right according to IEEE since the third bit is undefined. Priscilla At 03:32 PM 3/22/01, John Neiberger wrote: >Okay, now I'm confused by something in the Sybex CCIE study guide in the >token ring chapter. It says that if the first two bits of the routing >control field are 10 the frame is an all-routes explorer. If the first >two bits are 11 then it's a single-route explorer. > >In all of their examples, when they convert the first nibble to hex >they use A for allroutes explorer and C to indicate single route >explorer. I understand "C" because 1100 = C, but 1000 = 8, not A. >What's the deal? Am I losing my mind or is the book wrong? I've >noticed the book has been wrong in several other places but this is a >new topic for me. > > From what I can tell, a RIF that starts with 8 is an all-routes >explorer. If it starts with C it is a single-route explorer. If it >starts with zero it is a nonexplorer frame. Is this correct? > >Thanks, >John > >_ >FAQ, list archives, and subscription info: >http://www.groupstudy.com/list/cisco.html >Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] Priscilla Oppenheimer http://www.priscilla.com _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
