BGP Dampening, What is a flap? [7:1128]
Greetings All I am in the process of writing a BGP class, at present I am specifically working on a section covering dampening. My question is "what is a flap" The two possible answers are: Answer one A flap is whenever path information changes for a route. By this definition if a route goes away, that would be a flap. When the route comes back, that would be another flap. So a route going away then coming back would be 2 flaps. Answer two A flap is a route transition from up to down back to up. So a route going away then coming back would count as one flap. I am mucking with this in my lab and the lab would seem to indicate that answer two is the correct one, but when I read the Sam Halabi copyright 1997 internet routing architectures book, page 440 and 441 it says the answer is Answer one. I am at best confused Any help? Tom Pruneau Trainer Network Operations GENUITY 3 Van de Graff Drive Burlington Ma. 01803 24 Hr. Network Operations Center 800-436-8489 If you need to get a hold of me my hours are 8AM-4PM ET Mon-Fri --- This email is composed of 82% post consumer recycled data bits --- "Once in a while you get shown the light in the strangest of places if you look at it right" Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=1128&t=1128 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: BGP Dampening, What is a flap? [7:1128]
My vote would be #2. Simply based on the definition of the verb 'flap': "To wave ... up *and* down." [emphasis added] http://www.dictionary.com/cgi-bin/dict.pl?term=flap ---JRE--- ""Tom Pruneau"" wrote in message [EMAIL PROTECTED]">news:[EMAIL PROTECTED]... > Greetings All > > I am in the process of writing a BGP class, at present I am specifically > working on a section covering dampening. > > My question is "what is a flap" > > The two possible answers are: > > > Answer one > A flap is whenever path information changes for a route. By this definition > if a route goes away, that would be a flap. When the route comes back, that > would be another flap. > So a route going away then coming back would be 2 flaps. > > > Answer two > A flap is a route transition from up to down back to up. So a route going > away then coming back would count as one flap. > > > > I am mucking with this in my lab and the lab would seem to indicate that > answer two is the correct one, but when I read the Sam Halabi copyright > 1997 internet routing architectures book, page 440 and 441 it says the > answer is Answer one. > > I am at best confused > > Any help? > Tom Pruneau > Trainer Network Operations > > GENUITY > 3 Van de Graff Drive Burlington Ma. 01803 > 24 Hr. Network Operations Center 800-436-8489 > If you need to get a hold of me my hours are 8AM-4PM ET Mon-Fri > > -- - > This email is composed of 82% post consumer recycled data bits > -- - > > "Once in a while you get shown the light > in the strangest of places if you look at it right" > FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html > Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=1132&t=1128 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: BGP Dampening, What is a flap? [7:1128]
A flap occurs when a router receives an advertisement for a prefix and then subsequently receives a "withdraw" update. That is one flap. If it comes up and goes back down again, that is two flaps total. At least, that's how I remember it. Someone please correct me if I'm wrong. Regards, John >>> "Jim Erickson" 4/18/01 1:52:18 PM >>> My vote would be #2. Simply based on the definition of the verb 'flap': "To wave ... up *and* down." [emphasis added] http://www.dictionary.com/cgi-bin/dict.pl?term=flap ---JRE--- ""Tom Pruneau"" wrote in message [EMAIL PROTECTED]">news:[EMAIL PROTECTED]... > Greetings All > > I am in the process of writing a BGP class, at present I am specifically > working on a section covering dampening. > > My question is "what is a flap" > > The two possible answers are: > > > Answer one > A flap is whenever path information changes for a route. By this definition > if a route goes away, that would be a flap. When the route comes back, that > would be another flap. > So a route going away then coming back would be 2 flaps. > > > Answer two > A flap is a route transition from up to down back to up. So a route going > away then coming back would count as one flap. > > > > I am mucking with this in my lab and the lab would seem to indicate that > answer two is the correct one, but when I read the Sam Halabi copyright > 1997 internet routing architectures book, page 440 and 441 it says the > answer is Answer one. > > I am at best confused > > Any help? > Tom Pruneau > Trainer Network Operations > > GENUITY > 3 Van de Graff Drive Burlington Ma. 01803 > 24 Hr. Network Operations Center 800-436-8489 > If you need to get a hold of me my hours are 8AM-4PM ET Mon-Fri > > -- - > This email is composed of 82% post consumer recycled data bits > -- - > > "Once in a while you get shown the light > in the strangest of places if you look at it right" > 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] Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=1136&t=1128 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: BGP Dampening, What is a flap? [7:1128]
I think from BGP's point of view a flap is a withdrawal and announcement of a routing prefix. Howard Berkowitz will know for sure. Did you check his BGP papers at http://www.certificationzone.com. Also there's a good paper here: http://www.ripe.net/ripe/docs/ripe-178.html Cisco often uses the word "flapping" in a generic sense for a route or interface going up and down repeatedly. That could be cause for some confusion. In your class, you might want to be clear about whether you are using the term generically or with reference to parameters to route dampening commands. Good luck. Let us know what you find out for sure! Thanks. Priscilla At 03:35 PM 4/18/01, Tom Pruneau wrote: >Greetings All > >I am in the process of writing a BGP class, at present I am specifically >working on a section covering dampening. > >My question is "what is a flap" > >The two possible answers are: > > >Answer one >A flap is whenever path information changes for a route. By this definition >if a route goes away, that would be a flap. When the route comes back, that >would be another flap. >So a route going away then coming back would be 2 flaps. > > >Answer two >A flap is a route transition from up to down back to up. So a route going >away then coming back would count as one flap. > > > >I am mucking with this in my lab and the lab would seem to indicate that >answer two is the correct one, but when I read the Sam Halabi copyright >1997 internet routing architectures book, page 440 and 441 it says the >answer is Answer one. > >I am at best confused > >Any help? >Tom Pruneau >Trainer Network Operations > >GENUITY >3 Van de Graff Drive Burlington Ma. 01803 >24 Hr. Network Operations Center 800-436-8489 >If you need to get a hold of me my hours are 8AM-4PM ET Mon-Fri > >--- >This email is composed of 82% post consumer recycled data bits >--- > >"Once in a while you get shown the light >in the strangest of places if you look at it right" >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 Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=1148&t=1128 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: BGP Dampening, What is a flap? [7:1128]
I always thought of a "Flap" as a generic term meaning when a route/interface/serial-line goes full-circle. from:- workingdowninitialisingup i have always treated the "whole" as one flap? Am i going mad. Cheers steve >From: "Priscilla Oppenheimer" >Reply-To: "Priscilla Oppenheimer" >To: [EMAIL PROTECTED] >Subject: Re: BGP Dampening, What is a flap? [7:1128] >Date: Wed, 18 Apr 2001 18:09:50 -0400 > >I think from BGP's point of view a flap is a withdrawal and announcement of >a routing prefix. Howard Berkowitz will know for sure. Did you check his >BGP papers at http://www.certificationzone.com. Also there's a good paper >here: > >http://www.ripe.net/ripe/docs/ripe-178.html > >Cisco often uses the word "flapping" in a generic sense for a route or >interface going up and down repeatedly. That could be cause for some >confusion. In your class, you might want to be clear about whether you are >using the term generically or with reference to parameters to route >dampening commands. > >Good luck. Let us know what you find out for sure! Thanks. > >Priscilla > >At 03:35 PM 4/18/01, Tom Pruneau wrote: > >Greetings All > > > >I am in the process of writing a BGP class, at present I am specifically > >working on a section covering dampening. > > > >My question is "what is a flap" > > > >The two possible answers are: > > > > > >Answer one > >A flap is whenever path information changes for a route. By this >definition > >if a route goes away, that would be a flap. When the route comes back, >that > >would be another flap. > >So a route going away then coming back would be 2 flaps. > > > > > >Answer two > >A flap is a route transition from up to down back to up. So a route going > >away then coming back would count as one flap. > > > > > > > >I am mucking with this in my lab and the lab would seem to indicate that > >answer two is the correct one, but when I read the Sam Halabi copyright > >1997 internet routing architectures book, page 440 and 441 it says the > >answer is Answer one. > > > >I am at best confused > > > >Any help? > >Tom Pruneau > >Trainer Network Operations > > > >GENUITY > >3 Van de Graff Drive Burlington Ma. 01803 > >24 Hr. Network Operations Center 800-436-8489 > >If you need to get a hold of me my hours are 8AM-4PM ET Mon-Fri > > > >--- > >This email is composed of 82% post consumer recycled data bits > >--- > > > >"Once in a while you get shown the light > >in the strangest of places if you look at it right" > >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] _ Get Your Private, Free E-mail from MSN Hotmail at http://www.hotmail.com. Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=1193&t=1128 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: BGP Dampening, What is a flap? [7:1128]
I always thought of a "Flap" as a generic term meaning when a route/interface/serial-line goes full-circle.regardless of protocol i use the term interchangeably with OSPF,PpP,LEASED lines,BGP,ISDN from:- workingdowninitialisingup i have always treated the "whole" as one flap? Am i going mad. Cheers steve "my mum always said it`s only an exam...PAH...what the heck do she know" >From: "Priscilla Oppenheimer" >Reply-To: "Priscilla Oppenheimer" >To: [EMAIL PROTECTED] >Subject: Re: BGP Dampening, What is a flap? [7:1128] >Date: Wed, 18 Apr 2001 18:09:50 -0400 > >I think from BGP's point of view a flap is a withdrawal and announcement of >a routing prefix. Howard Berkowitz will know for sure. Did you check his >BGP papers at http://www.certificationzone.com. Also there's a good paper >here: > >http://www.ripe.net/ripe/docs/ripe-178.html > >Cisco often uses the word "flapping" in a generic sense for a route or >interface going up and down repeatedly. That could be cause for some >confusion. In your class, you might want to be clear about whether you are >using the term generically or with reference to parameters to route >dampening commands. > >Good luck. Let us know what you find out for sure! Thanks. > >Priscilla > >At 03:35 PM 4/18/01, Tom Pruneau wrote: > >Greetings All > > > >I am in the process of writing a BGP class, at present I am specifically > >working on a section covering dampening. > > > >My question is "what is a flap" > > > >The two possible answers are: > > > > > >Answer one > >A flap is whenever path information changes for a route. By this >definition > >if a route goes away, that would be a flap. When the route comes back, >that > >would be another flap. > >So a route going away then coming back would be 2 flaps. > > > > > >Answer two > >A flap is a route transition from up to down back to up. So a route going > >away then coming back would count as one flap. > > > > > > > >I am mucking with this in my lab and the lab would seem to indicate that > >answer two is the correct one, but when I read the Sam Halabi copyright > >1997 internet routing architectures book, page 440 and 441 it says the > >answer is Answer one. > > > >I am at best confused > > > >Any help? > >Tom Pruneau > >Trainer Network Operations > > > >GENUITY > >3 Van de Graff Drive Burlington Ma. 01803 > >24 Hr. Network Operations Center 800-436-8489 > >If you need to get a hold of me my hours are 8AM-4PM ET Mon-Fri > > > >--- > >This email is composed of 82% post consumer recycled data bits > >--- > > > >"Once in a while you get shown the light > >in the strangest of places if you look at it right" > >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] _ Get Your Private, Free E-mail from MSN Hotmail at http://www.hotmail.com. Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=1194&t=1128 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
RE: BGP Dampening, What is a flap? [7:1128]
Please let me quote from sitamoth.com: Route dampening is a BGP feature designed to minimize the propagation of flapping routes across an internetwork. A route is considered to be flapping when it is repeatedly available, then unavailable, then available then unavailable..and so on. A route that is flapping receives a penalty of 1000 for each flap. When the accumulated pelanlty reaches a configurable limit, BGP surpresses advertisement of the route EVEN if the route is UP. The accumulated penalty is decremented by the half-life time. When the accumulated penalty is less than the reuse limit, the route is advertised again (if it is still UP). Hope this can help :) Andy -Original Message- From: Stephen Skinner [mailto:[EMAIL PROTECTED]] Sent: Thursday, April 19, 2001 3:53 PM To: [EMAIL PROTECTED] Subject: Re: BGP Dampening, What is a flap? [7:1128] I always thought of a "Flap" as a generic term meaning when a route/interface/serial-line goes full-circle.regardless of protocol i use the term interchangeably with OSPF,PpP,LEASED lines,BGP,ISDN from:- workingdowninitialisingup i have always treated the "whole" as one flap? Am i going mad. Cheers steve "my mum always said it`s only an exam...PAH...what the heck do she know" >From: "Priscilla Oppenheimer" >Reply-To: "Priscilla Oppenheimer" >To: [EMAIL PROTECTED] >Subject: Re: BGP Dampening, What is a flap? [7:1128] >Date: Wed, 18 Apr 2001 18:09:50 -0400 > >I think from BGP's point of view a flap is a withdrawal and announcement of >a routing prefix. Howard Berkowitz will know for sure. Did you check his >BGP papers at http://www.certificationzone.com. Also there's a good paper >here: > >http://www.ripe.net/ripe/docs/ripe-178.html > >Cisco often uses the word "flapping" in a generic sense for a route or >interface going up and down repeatedly. That could be cause for some >confusion. In your class, you might want to be clear about whether you are >using the term generically or with reference to parameters to route >dampening commands. > >Good luck. Let us know what you find out for sure! Thanks. > >Priscilla > >At 03:35 PM 4/18/01, Tom Pruneau wrote: > >Greetings All > > > >I am in the process of writing a BGP class, at present I am specifically > >working on a section covering dampening. > > > >My question is "what is a flap" > > > >The two possible answers are: > > > > > >Answer one > >A flap is whenever path information changes for a route. By this >definition > >if a route goes away, that would be a flap. When the route comes back, >that > >would be another flap. > >So a route going away then coming back would be 2 flaps. > > > > > >Answer two > >A flap is a route transition from up to down back to up. So a route going > >away then coming back would count as one flap. > > > > > > > >I am mucking with this in my lab and the lab would seem to indicate that > >answer two is the correct one, but when I read the Sam Halabi copyright > >1997 internet routing architectures book, page 440 and 441 it says the > >answer is Answer one. > > > >I am at best confused > > > >Any help? > >Tom Pruneau > >Trainer Network Operations > > > >GENUITY > >3 Van de Graff Drive Burlington Ma. 01803 > >24 Hr. Network Operations Center 800-436-8489 > >If you need to get a hold of me my hours are 8AM-4PM ET Mon-Fri > > > >--- > >This email is composed of 82% post consumer recycled data bits > >--- > > > >"Once in a while you get shown the light > >in the strangest of places if you look at it right" > >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] _ Get Your Private, Free E-mail from MSN Hotmail at http://www.hotmail.com. FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=1195&t=1128 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
RE: BGP Dampening, What is a flap? [7:1128]
hooray . it looks like as thought i was right about the term flap..just wrong about BGP ..thanks for the info chhers steve >From: Andy Prima >To: "'Stephen Skinner'" , [EMAIL PROTECTED] >Subject: RE: BGP Dampening, What is a flap? [7:1128] >Date: Thu, 19 Apr 2001 16:19:26 +0700 > > >Please let me quote from sitamoth.com: > >Route dampening is a BGP feature designed to minimize the propagation of >flapping routes across an internetwork. A route is considered to be >flapping >when it is repeatedly available, then unavailable, then available then >unavailable..and so on. >A route that is flapping receives a penalty of 1000 for each flap. When the >accumulated pelanlty reaches a configurable limit, BGP surpresses >advertisement of the route EVEN if the route is UP. >The accumulated penalty is decremented by the half-life time. When the >accumulated penalty is less than the reuse limit, the route is advertised >again (if it is still UP). > > >Hope this can help :) > >Andy > >-Original Message- >From: Stephen Skinner [mailto:[EMAIL PROTECTED]] >Sent: Thursday, April 19, 2001 3:53 PM >To: [EMAIL PROTECTED] >Subject: Re: BGP Dampening, What is a flap? [7:1128] > > >I always thought of a "Flap" as a generic term meaning when a >route/interface/serial-line goes full-circle.regardless of protocol >i use the term interchangeably with OSPF,PpP,LEASED lines,BGP,ISDN > >from:- workingdowninitialisingup > >i have always treated the "whole" as one flap? > >Am i going mad. > >Cheers > >steve > >"my mum always said it`s only an exam.......PAH...what the heck do she >know" > > > >From: "Priscilla Oppenheimer" > >Reply-To: "Priscilla Oppenheimer" > >To: [EMAIL PROTECTED] > >Subject: Re: BGP Dampening, What is a flap? [7:1128] > >Date: Wed, 18 Apr 2001 18:09:50 -0400 > > > >I think from BGP's point of view a flap is a withdrawal and announcement >of > >a routing prefix. Howard Berkowitz will know for sure. Did you check his > >BGP papers at http://www.certificationzone.com. Also there's a good paper > >here: > > > >http://www.ripe.net/ripe/docs/ripe-178.html > > > >Cisco often uses the word "flapping" in a generic sense for a route or > >interface going up and down repeatedly. That could be cause for some > >confusion. In your class, you might want to be clear about whether you >are > >using the term generically or with reference to parameters to route > >dampening commands. > > > >Good luck. Let us know what you find out for sure! Thanks. > > > >Priscilla > > > >At 03:35 PM 4/18/01, Tom Pruneau wrote: > > >Greetings All > > > > > >I am in the process of writing a BGP class, at present I am >specifically > > >working on a section covering dampening. > > > > > >My question is "what is a flap" > > > > > >The two possible answers are: > > > > > > > > >Answer one > > >A flap is whenever path information changes for a route. By this > >definition > > >if a route goes away, that would be a flap. When the route comes back, > >that > > >would be another flap. > > >So a route going away then coming back would be 2 flaps. > > > > > > > > >Answer two > > >A flap is a route transition from up to down back to up. So a route >going > > >away then coming back would count as one flap. > > > > > > > > > > > >I am mucking with this in my lab and the lab would seem to indicate >that > > >answer two is the correct one, but when I read the Sam Halabi copyright > > >1997 internet routing architectures book, page 440 and 441 it says the > > >answer is Answer one. > > > > > >I am at best confused > > > > > >Any help? > > >Tom Pruneau > > >Trainer Network Operations > > > > > >GENUITY > > >3 Van de Graff Drive Burlington Ma. 01803 > > >24 Hr. Network Operations Center 800-436-8489 > > >If you need to get a hold of me my hours are 8AM-4PM ET Mon-Fri > > > > > > >--- > > >This email is composed of 82% post consumer recycled data bits > > > >--- > > > > > >"Once in a while you get shown the light > > >in the strangest of places if you loo
RE: BGP Dampening, What is a flap? [7:1128]
It doesn't answer the question. It says there's a penalty for each flap. Is there a penalty for 1. each time a route goes down or 2. each time a route goes down and back up The answer is probably number 2, as the orignal poster thought also, since just going down isn't really "flapping." Priscilla At 05:18 AM 4/19/01, Andy Prima wrote: >Please let me quote from sitamoth.com: > >Route dampening is a BGP feature designed to minimize the propagation of >flapping routes across an internetwork. A route is considered to be flapping >when it is repeatedly available, then unavailable, then available then >unavailable..and so on. >A route that is flapping receives a penalty of 1000 for each flap. When the >accumulated pelanlty reaches a configurable limit, BGP surpresses >advertisement of the route EVEN if the route is UP. >The accumulated penalty is decremented by the half-life time. When the >accumulated penalty is less than the reuse limit, the route is advertised >again (if it is still UP). > > >Hope this can help :) > >Andy > >-Original Message- >From: Stephen Skinner [mailto:[EMAIL PROTECTED]] >Sent: Thursday, April 19, 2001 3:53 PM >To: [EMAIL PROTECTED] >Subject: Re: BGP Dampening, What is a flap? [7:1128] > > >I always thought of a "Flap" as a generic term meaning when a >route/interface/serial-line goes full-circle.regardless of protocol >i use the term interchangeably with OSPF,PpP,LEASED lines,BGP,ISDN > >from:- workingdowninitialisingup > >i have always treated the "whole" as one flap? > >Am i going mad. > >Cheers > >steve > >"my mum always said it`s only an exam...PAH...what the heck do she >know" > > > >From: "Priscilla Oppenheimer" > >Reply-To: "Priscilla Oppenheimer" > >To: [EMAIL PROTECTED] > >Subject: Re: BGP Dampening, What is a flap? [7:1128] > >Date: Wed, 18 Apr 2001 18:09:50 -0400 > > > >I think from BGP's point of view a flap is a withdrawal and announcement of > >a routing prefix. Howard Berkowitz will know for sure. Did you check his > >BGP papers at http://www.certificationzone.com. Also there's a good paper > >here: > > > >http://www.ripe.net/ripe/docs/ripe-178.html > > > >Cisco often uses the word "flapping" in a generic sense for a route or > >interface going up and down repeatedly. That could be cause for some > >confusion. In your class, you might want to be clear about whether you are > >using the term generically or with reference to parameters to route > >dampening commands. > > > >Good luck. Let us know what you find out for sure! Thanks. > > > >Priscilla > > > >At 03:35 PM 4/18/01, Tom Pruneau wrote: > > >Greetings All > > > > > >I am in the process of writing a BGP class, at present I am specifically > > >working on a section covering dampening. > > > > > >My question is "what is a flap" > > > > > >The two possible answers are: > > > > > > > > >Answer one > > >A flap is whenever path information changes for a route. By this > >definition > > >if a route goes away, that would be a flap. When the route comes back, > >that > > >would be another flap. > > >So a route going away then coming back would be 2 flaps. > > > > > > > > >Answer two > > >A flap is a route transition from up to down back to up. So a route going > > >away then coming back would count as one flap. > > > > > > > > > > > >I am mucking with this in my lab and the lab would seem to indicate that > > >answer two is the correct one, but when I read the Sam Halabi copyright > > >1997 internet routing architectures book, page 440 and 441 it says the > > >answer is Answer one. > > > > > >I am at best confused > > > > > >Any help? > > >Tom Pruneau > > >Trainer Network Operations > > > > > >GENUITY > > >3 Van de Graff Drive Burlington Ma. 01803 > > >24 Hr. Network Operations Center 800-436-8489 > > >If you need to get a hold of me my hours are 8AM-4PM ET Mon-Fri > > > > > > >--- > > >This email is composed of 82% post consumer recycled data bits > > > >--- > > > > > >"Once in a while you get shown the light > > >in the strangest of places
Re: BGP Dampening, What is a flap? [7:1128]
And it's all tied to time as well, so just don't go down/up within a very short period (just go down, do your work, then back up). If you know you're going to take a BGP announcing router offline and don't want there to be any possibility of things bouncing while you're working, shutdown your BGP neighbors so you won't be announcing and then withdrawing them. So long as I've done that, I've never had dampening problems. When I'm all done, I just no shutdown the BGP neighbors and we've got no dampening penalties. Before learning about the BGP neighbor shutdown command, I was getting dampened a bit as the serial line would sometimes bounce when first coming up and the BGP neighbors were already exchanging routes. Also important is to kill your iBGP neighbors statements as well (shutdown command), as you don't want them to be flapping any routes that originate from the router you're working on. An example of the command: router bgp 18506 neighbor 63.123.123.166 shutdown Worst case, when I was first installing BGP and tweaking with memory and how many routes we could hold (and crashing and losing our BGP sessions), I think I probably flapped 10 times and got dampened for 2 hours from some ISPs. Of course, we were working after hours so no big deal, but now that I know better I wouldn't announce any routes until I knew everything else was stable. BGP looking glasses are very useful to see if you're getting dampened ;-) telnet://route-views.oregon-ix.net telnet://route-server.cerf.net -- Jason Roysdon, CCNP+Security/CCDP, MCSE, CNA, Network+, A+ List email: [EMAIL PROTECTED] Homepage: http://jason.artoo.net/ ""Priscilla Oppenheimer"" wrote in message [EMAIL PROTECTED]">news:[EMAIL PROTECTED]... > It doesn't answer the question. It says there's a penalty for each flap. Is > there a penalty for > > 1. each time a route goes down > or > 2. each time a route goes down and back up > > The answer is probably number 2, as the orignal poster thought also, since > just going down isn't really "flapping." > > Priscilla > > At 05:18 AM 4/19/01, Andy Prima wrote: > >Please let me quote from sitamoth.com: > > > >Route dampening is a BGP feature designed to minimize the propagation of > >flapping routes across an internetwork. A route is considered to be flapping > >when it is repeatedly available, then unavailable, then available then > >unavailable..and so on. > >A route that is flapping receives a penalty of 1000 for each flap. When the > >accumulated pelanlty reaches a configurable limit, BGP surpresses > >advertisement of the route EVEN if the route is UP. > >The accumulated penalty is decremented by the half-life time. When the > >accumulated penalty is less than the reuse limit, the route is advertised > >again (if it is still UP). > > > > > >Hope this can help :) > > > >Andy > > > >-Original Message- > >From: Stephen Skinner [mailto:[EMAIL PROTECTED]] > >Sent: Thursday, April 19, 2001 3:53 PM > >To: [EMAIL PROTECTED] > >Subject: Re: BGP Dampening, What is a flap? [7:1128] > > > > > >I always thought of a "Flap" as a generic term meaning when a > >route/interface/serial-line goes full-circle.regardless of protocol > >i use the term interchangeably with OSPF,PpP,LEASED lines,BGP,ISDN > > > >from:- workingdown----initialisingup > > > >i have always treated the "whole" as one flap? > > > >Am i going mad. > > > >Cheers > > > >steve > > > >"my mum always said it`s only an exam...PAH...what the heck do she > >know" > > > > > > >From: "Priscilla Oppenheimer" > > >Reply-To: "Priscilla Oppenheimer" > > >To: [EMAIL PROTECTED] > > >Subject: Re: BGP Dampening, What is a flap? [7:1128] > > >Date: Wed, 18 Apr 2001 18:09:50 -0400 > > > > > >I think from BGP's point of view a flap is a withdrawal and announcement > of > > >a routing prefix. Howard Berkowitz will know for sure. Did you check his > > >BGP papers at http://www.certificationzone.com. Also there's a good paper > > >here: > > > > > >http://www.ripe.net/ripe/docs/ripe-178.html > > > > > >Cisco often uses the word "flapping" in a generic sense for a route or > > >interface going up and down repeatedly. That could be cause for some > > >confusion. In your class, you might want to be clear about whether you are > > >using the term generically or with reference to parameters to route >
Re: BGP Dampening, What is a flap? [7:1128]
Coming into this discussion a little late, it's important to distinguish between flaps and flapping. Flaps are single events: the cycle of announce/withdraw/announce over a short period of time. Various timing parameters influence the point at which flaps become flapping. Some providers have additional conditional elements -- they are less tolerant of flapping on long prefixes -- they would put up with more flapping on a /19 than on a /24. As an aside, both Cisco and IETF documents are inconsistent about calling the countermeasure damping or dampening. In control system theory, the correct term is damping. As a gardener, however, dampening is a good thing to do to seedlings, making them moist and green. A damped seedling has gone limp and is on its way to the Great Compost Pile in the Sky. >And it's all tied to time as well, so just don't go down/up within a very >short period (just go down, do your work, then back up). If you know you're >going to take a BGP announcing router offline and don't want there to be any >possibility of things bouncing while you're working, shutdown your BGP >neighbors so you won't be announcing and then withdrawing them. So long as >I've done that, I've never had dampening problems. When I'm all done, I >just no shutdown the BGP neighbors and we've got no dampening penalties. >Before learning about the BGP neighbor shutdown command, I was getting >dampened a bit as the serial line would sometimes bounce when first coming >up and the BGP neighbors were already exchanging routes. Also important is >to kill your iBGP neighbors statements as well (shutdown command), as you >don't want them to be flapping any routes that originate from the router >you're working on. An example of the command: >router bgp 18506 > neighbor 63.123.123.166 shutdown > >Worst case, when I was first installing BGP and tweaking with memory and how >many routes we could hold (and crashing and losing our BGP sessions), I >think I probably flapped 10 times and got dampened for 2 hours from some >ISPs. Of course, we were working after hours so no big deal, but now that I >know better I wouldn't announce any routes until I knew everything else was >stable. > >BGP looking glasses are very useful to see if you're getting dampened ;-) >telnet://route-views.oregon-ix.net >telnet://route-server.cerf.net > >-- >Jason Roysdon, CCNP+Security/CCDP, MCSE, CNA, Network+, A+ >List email: [EMAIL PROTECTED] >Homepage: http://jason.artoo.net/ > > > >""Priscilla Oppenheimer"" wrote in message >[EMAIL PROTECTED]">news:[EMAIL PROTECTED]... >> It doesn't answer the question. It says there's a penalty for each flap. >Is >> there a penalty for >> >> 1. each time a route goes down >> or >> 2. each time a route goes down and back up >> >> The answer is probably number 2, as the orignal poster thought also, since >> just going down isn't really "flapping." >> >> Priscilla >> >> At 05:18 AM 4/19/01, Andy Prima wrote: >> >Please let me quote from sitamoth.com: >> > >> >Route dampening is a BGP feature designed to minimize the propagation of >> >flapping routes across an internetwork. A route is considered to be >flapping >> >when it is repeatedly available, then unavailable, then available then >> >unavailable..and so on. >> >A route that is flapping receives a penalty of 1000 for each flap. When >the >> >accumulated pelanlty reaches a configurable limit, BGP surpresses >> >advertisement of the route EVEN if the route is UP. >> >The accumulated penalty is decremented by the half-life time. When the >> >accumulated penalty is less than the reuse limit, the route is advertised >> >again (if it is still UP). >> > >> > >> >Hope this can help :) >> > >> >Andy >> > >> >-Original Message- >> >From: Stephen Skinner [mailto:[EMAIL PROTECTED]] >> >Sent: Thursday, April 19, 2001 3:53 PM >> >To: [EMAIL PROTECTED] >> >Subject: Re: BGP Dampening, What is a flap? [7:1128] >> > >> > >> >I always thought of a "Flap" as a generic term meaning when a >> >route/interface/serial-line goes full-circle.regardless of protocol > > >i use the term interchangeably with OSPF,PpP,LEASED lines,BGP,ISDN >> > >> >from:- workingdowninitialisingup >> > >> >i have always treated the "whole" as one flap? >> > >> >Am i going mad.
RE: BGP Dampening, What is a flap? [7:1128]
On Thu, 19 Apr 2001, Priscilla Oppenheimer wrote: > It doesn't answer the question. It says there's a penalty for each flap. Is > there a penalty for > > 1. each time a route goes down > or > 2. each time a route goes down and back up > > The answer is probably number 2, as the orignal poster thought also, since > just going down isn't really "flapping." Well, maybe I'm missing something, but I don't see how a route could go down more than once without going up meanwhile, or up more than once without going down meanwhile. So 1 and 2 are pretty much the same thing, except perhaps for an extra up or down at either end. OTOH, it could be that some BGP implementations send several WITHDRAWS in a row, or that a single route going down may result in a given router getting several withdraws (eg, redundant route reflectors, or multiple peers advertizing the same prefix). Does someone know whether 1- BGP protocol definition allows sending several WITHDRAWS to the same peer for a single up-down transition and 2- routers apply the flap penalty repeatedly when they get a WITHDRAW for a prefix already marked down? -- "Someone approached me and asked me to teach a javascript course. I was about to decline, saying that my complete ignorance of the subject made me unsuitable, then I thought again, that maybe it doesn't, as driving people away from it is a desirable outcome." --Me Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=1322&t=1128 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
RE: BGP Dampening, What is a flap? [7:1128]
Ok...it seems this topic is divided 1.GBP flaps/flapping 2.flapping in general as regards 1 i don`t claim to know the answer but i think a FAIR description of a flapping route/interface would be this "the route has gone down and come back up again BEFORE the router has had time to Re-converge/update routing tables" with singular instances bieng a "flap" and multiple instances bieng "flapping" Would this be a fair overall description.if i am right then it`s a small step to finding out why/how BGP does it Thanks steve >From: "ElephantChild" >Reply-To: "ElephantChild" >To: [EMAIL PROTECTED] >Subject: RE: BGP Dampening, What is a flap? [7:1128] >Date: Thu, 19 Apr 2001 20:39:20 -0400 > >On Thu, 19 Apr 2001, Priscilla Oppenheimer wrote: > > > It doesn't answer the question. It says there's a penalty for each flap. >Is > > there a penalty for > > > > 1. each time a route goes down > > or > > 2. each time a route goes down and back up > > > > The answer is probably number 2, as the orignal poster thought also, >since > > just going down isn't really "flapping." > >Well, maybe I'm missing something, but I don't see how a route could go >down more than once without going up meanwhile, or up more than once >without going down meanwhile. So 1 and 2 are pretty much the same thing, >except perhaps for an extra up or down at either end. OTOH, it could be >that some BGP implementations send several WITHDRAWS in a row, or that a >single route going down may result in a given router getting several >withdraws (eg, redundant route reflectors, or multiple peers advertizing >the same prefix). Does someone know whether 1- BGP protocol definition >allows sending several WITHDRAWS to the same peer for a single up-down >transition and 2- routers apply the flap penalty repeatedly when they get a >WITHDRAW for a prefix already marked down? > >-- >"Someone approached me and asked me to teach a javascript course. I was >about to decline, saying that my complete ignorance of the subject made >me unsuitable, then I thought again, that maybe it doesn't, as driving >people away from it is a desirable outcome." --Me >FAQ, list archives, and subscription info: >http://www.groupstudy.com/list/cisco.html >Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] _ Get Your Private, Free E-mail from MSN Hotmail at http://www.hotmail.com. Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=1341&t=1128 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: BGP Dampening, What is a flap? [7:1128]
Answer 1 is correct. A flap is one transition, either from down to up or from up to down. ""Tom Pruneau"" wrote in message [EMAIL PROTECTED]">news:[EMAIL PROTECTED]... > Greetings All > > I am in the process of writing a BGP class, at present I am specifically > working on a section covering dampening. > > My question is "what is a flap" > > The two possible answers are: > > > Answer one > A flap is whenever path information changes for a route. By this definition > if a route goes away, that would be a flap. When the route comes back, that > would be another flap. > So a route going away then coming back would be 2 flaps. > > > Answer two > A flap is a route transition from up to down back to up. So a route going > away then coming back would count as one flap. > > > > I am mucking with this in my lab and the lab would seem to indicate that > answer two is the correct one, but when I read the Sam Halabi copyright > 1997 internet routing architectures book, page 440 and 441 it says the > answer is Answer one. > > I am at best confused > > Any help? > Tom Pruneau > Trainer Network Operations > > GENUITY > 3 Van de Graff Drive Burlington Ma. 01803 > 24 Hr. Network Operations Center 800-436-8489 > If you need to get a hold of me my hours are 8AM-4PM ET Mon-Fri > > -- - > This email is composed of 82% post consumer recycled data bits > -- - > > "Once in a while you get shown the light > in the strangest of places if you look at it right" > FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html > Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=2435&t=1128 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
OT: Ramblings [Was Re: BGP Dampening, What is a flap? [7:1128]
Speaking of, I'll be posting pics of my compost bin, router rack, and firepit on my homepage tonight. These are my hobbies, I'm a homebody geek, and I like my life as it is, thankyouverymuch *g* One of these days I'll get a digital camera so it doesn't take me 4 steps to get photos up my website instead of just 1. A scanner would help, so at least then I wouldn't have to go to the office (I think I've been in the office twice this month, once to pick up parts, and today to scan the photos). Hmm, so I guess I'm a frugal geek. Oh, what a coincidence, Star Trek Voyager re-run tonight just used dampening. Chakotay (sp?) said, "I'm detecting a dampening field around that building." That settles it, Star Trek is made up babbling and usually incorrect when it comes to technical terms (unlike Star Wars, you know), so it must be damping *g* -- Jason Roysdon, CCNP+Security/CCDP, MCSE, CNA, Network+, A+ List email: [EMAIL PROTECTED] Homepage: http://jason.artoo.net/ ""Howard C. Berkowitz"" wrote in message [EMAIL PROTECTED]">news:[EMAIL PROTECTED]... > As a gardener, however, dampening is a good thing to do to seedlings, > making them moist and green. A damped seedling has gone limp and is > on its way to the Great Compost Pile in the Sky. > Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=1337&t=1128 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
