Re: BGP: IBGP usage/clarification [7:15333]
""Chuck Larrieu"" wrote in message [EMAIL PROTECTED]">news:[EMAIL PROTECTED]... > reminder - for those without CCO accounts, substitute "public" for > "customer" Chuck Thanks for the correction The link is : http://www.cisco.com/warp/public/459/bgp-toc.html I forgot that I had logged in CCO and managed to put my foot in my mouth again ! Anyway for any subjects on all CCNP exams there is no substitute for the Cisco web site and if you are willing to search a bit you will certainly find gold (more details and explanations than the bare minimum for passing exams but I assume we all want to learn a bit more than just a textbook) George Yiannibas MCSE CCNA Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=15522&t=15333 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
RE: BGP: IBGP usage/clarification [7:15333]
Must give credit to Brian however for pointing out the need to run IBGP in situations where you have two routers recieving partial routes from ISP's. In these cases, IBGP helps you to make optimal exit decisions as he points out. I overlooked this in my previous pointing by taking things for granted. Glad to help. pete *** REPLY SEPARATOR *** On 8/8/2001 at 3:40 PM Ole Drews Jensen wrote: >Thanks once again Peter, > >I now have a much better understanding of the BGP. > >I can now jump on to some of the other areas where I'm still leaking a >little understanding, so I can get this BSCN exam over and done with. > >Thanks, > >Ole > >~~~ > Ole Drews Jensen > Systems Network Manager > CCNA, MCSE, MCP+I > RWR Enterprises, Inc. > [EMAIL PROTECTED] >~~~ > http://www.RouterChief.com >~~~ > NEED A JOB ??? > http://www.oledrews.com/job >~~~ > > > >-Original Message- >From: Peter Van Oene [mailto:[EMAIL PROTECTED]] >Sent: Wednesday, August 08, 2001 3:23 PM >To: Ole Drews Jensen; [EMAIL PROTECTED] >Subject: RE: BGP: IBGP usage/clarification [7:15333] > > >Comments inline > >*** REPLY SEPARATOR *** > >On 8/8/2001 at 2:48 PM Ole Drews Jensen wrote: > >>Thanks Peter. >> >>I have browsed through Howards's BGP series, but for me, sometimes too >long >>explanations are more frustrating than a 10 words fact. >> >>Two additional questions if you don't mind, and you have a minute or two >>:-) >> >>1) >> >>If you only have one BGP connection to one remote AS, IBGP would normally >>never be used, and you would in most cases create a static default route >to >>the BGP router and redistribute it in your IGP. Am I right? >> > >You are very correct and this is a typical use of default routing. IBGP by >definition has no place here as it is a protocol used between BGP peers in >the same AS and if you have only only router in the AS, nothing matches >that >criteria. > > >>2) >> >>Should you have multiple BGP routers in the AS connected to two different >>remote AS's - would I always configure IBGP between them, or would there >be >>situations where IBGP would still be unused? > >Keep in mind that IBGP distributes BGP learned routing information among >peering routers within an AS. Hence, if you want border routers A and B to >be aware of each others upstream connectivity, IBGP is your tool. Should >you be providing transit, that is to say you are advertising that you can >forward packets to destinations not originating in your AS, you will >definitely require this functionality. Without it, A may advertise >reachability to networks downstream of B that B, or other routers in the >transit path from A to B do not know about. In this case you would >blackhole those routes. > >In non transit AS's, your level of use of BGP can vary. If you have >multiple providers and some redundancy in the way of multiple BGP speaking >routers inside your AS, you could achieve gains in least cost forwarding by >using IBGP to ensure all BGP speakers had the most accurate reachability >information. It's really a balance here between how badly you need traffic >to take the most optimal path out of your network and much you want to >spend >on infrastructure. Default routing is an excellent tool :) > > > > >>Thanks again, >> >>Ole >> >>~~~ >> Ole Drews Jensen >> Systems Network Manager >> CCNA, MCSE, MCP+I >> RWR Enterprises, Inc. >> [EMAIL PROTECTED] >>~~~ >> http://www.RouterChief.com >>~~~ >> NEED A JOB ??? >> http://www.oledrews.com/job >>~~~ >> >> >>-Original Message- >>From: Peter Van Oene [mailto:[EMAIL PROTECTED]] >>Sent: Wednesday, August 08, 2001 2:38 PM >>To: Ole Drews Jensen; [EMAIL PROTECTED] >>Subject: Re: BGP: IBGP usage/clarification [7:15333] >> >> >>A couple quick notes. However I would suggest if you have a subscription >>that you step through Howards BGP series at www.certificationzone.com as >it >>might help you solidify your understanding. >> >>First off, IBGP is not an IGP. If you want to get from point A to point B >>in AS C, IBGP isn't your friend (unless operator X tweaked IBGP with lots >>of >>messiness -ie NHS everywhere etc) IBGP facili
RE: BGP: IBGP usage/clarification [7:15333]
Thanks to all of you who have replied to my messages, it has really helped me getting a much better feel for IBGP. Take care, Ole ~~~ Ole Drews Jensen Systems Network Manager CCNA, MCSE, MCP+I RWR Enterprises, Inc. [EMAIL PROTECTED] ~~~ http://www.RouterChief.com ~~~ NEED A JOB ??? http://www.oledrews.com/job ~~~ -Original Message- From: Chuck Larrieu [mailto:[EMAIL PROTECTED]] Sent: Thursday, August 09, 2001 2:28 AM To: [EMAIL PROTECTED] Subject: RE: BGP: IBGP usage/clarification [7:15333] reminder - for those without CCO accounts, substitute "public" for "customer" -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]] Sent: Thursday, August 09, 2001 12:05 AM To: [EMAIL PROTECTED] Subject: RE: BGP: IBGP usage/clarification [7:15333] Ole I am also studying for the Routing exam. If you want BGP4 explained I suggest the following link : http://www.cisco.com/warp/customer/459/bgp-toc.html Very good IMHO George Yiannibas MCSE CCNA Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=15454&t=15333 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
RE: BGP: IBGP usage/clarification [7:15333]
reminder - for those without CCO accounts, substitute "public" for "customer" -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]] Sent: Thursday, August 09, 2001 12:05 AM To: [EMAIL PROTECTED] Subject: RE: BGP: IBGP usage/clarification [7:15333] Ole I am also studying for the Routing exam. If you want BGP4 explained I suggest the following link : http://www.cisco.com/warp/customer/459/bgp-toc.html Very good IMHO George Yiannibas MCSE CCNA Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=15441&t=15333 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
RE: BGP: IBGP usage/clarification [7:15333]
Ole I am also studying for the Routing exam. If you want BGP4 explained I suggest the following link : http://www.cisco.com/warp/customer/459/bgp-toc.html Very good IMHO George Yiannibas MCSE CCNA Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=15439&t=15333 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
RE: BGP: IBGP usage/clarification [7:15333]
Thanks once again Peter, I now have a much better understanding of the BGP. I can now jump on to some of the other areas where I'm still leaking a little understanding, so I can get this BSCN exam over and done with. Thanks, Ole ~~~ Ole Drews Jensen Systems Network Manager CCNA, MCSE, MCP+I RWR Enterprises, Inc. [EMAIL PROTECTED] ~~~ http://www.RouterChief.com ~~~ NEED A JOB ??? http://www.oledrews.com/job ~~~ -Original Message- From: Peter Van Oene [mailto:[EMAIL PROTECTED]] Sent: Wednesday, August 08, 2001 3:23 PM To: Ole Drews Jensen; [EMAIL PROTECTED] Subject: RE: BGP: IBGP usage/clarification [7:15333] Comments inline *** REPLY SEPARATOR *** On 8/8/2001 at 2:48 PM Ole Drews Jensen wrote: >Thanks Peter. > >I have browsed through Howards's BGP series, but for me, sometimes too long >explanations are more frustrating than a 10 words fact. > >Two additional questions if you don't mind, and you have a minute or two >:-) > >1) > >If you only have one BGP connection to one remote AS, IBGP would normally >never be used, and you would in most cases create a static default route to >the BGP router and redistribute it in your IGP. Am I right? > You are very correct and this is a typical use of default routing. IBGP by definition has no place here as it is a protocol used between BGP peers in the same AS and if you have only only router in the AS, nothing matches that criteria. >2) > >Should you have multiple BGP routers in the AS connected to two different >remote AS's - would I always configure IBGP between them, or would there be >situations where IBGP would still be unused? Keep in mind that IBGP distributes BGP learned routing information among peering routers within an AS. Hence, if you want border routers A and B to be aware of each others upstream connectivity, IBGP is your tool. Should you be providing transit, that is to say you are advertising that you can forward packets to destinations not originating in your AS, you will definitely require this functionality. Without it, A may advertise reachability to networks downstream of B that B, or other routers in the transit path from A to B do not know about. In this case you would blackhole those routes. In non transit AS's, your level of use of BGP can vary. If you have multiple providers and some redundancy in the way of multiple BGP speaking routers inside your AS, you could achieve gains in least cost forwarding by using IBGP to ensure all BGP speakers had the most accurate reachability information. It's really a balance here between how badly you need traffic to take the most optimal path out of your network and much you want to spend on infrastructure. Default routing is an excellent tool :) >Thanks again, > >Ole > >~~~ > Ole Drews Jensen > Systems Network Manager > CCNA, MCSE, MCP+I > RWR Enterprises, Inc. > [EMAIL PROTECTED] >~~~ > http://www.RouterChief.com >~~~ > NEED A JOB ??? > http://www.oledrews.com/job >~~~ > > >-Original Message- >From: Peter Van Oene [mailto:[EMAIL PROTECTED]] >Sent: Wednesday, August 08, 2001 2:38 PM >To: Ole Drews Jensen; [EMAIL PROTECTED] >Subject: Re: BGP: IBGP usage/clarification [7:15333] > > >A couple quick notes. However I would suggest if you have a subscription >that you step through Howards BGP series at www.certificationzone.com as it >might help you solidify your understanding. > >First off, IBGP is not an IGP. If you want to get from point A to point B >in AS C, IBGP isn't your friend (unless operator X tweaked IBGP with lots >of >messiness -ie NHS everywhere etc) IBGP facilitates inter-AS routing by >enabling reachability information to be maintained within AS's. IGP are >still required to enable routing within the AS (ie intra-AS routing). > >IBGP is used when you have multiple BGP routers in an AS. Really not much >more to it than that at a high level. Whether or not you chose to use a >dynamic IGP versus a static configuration really is up to the administrator >with typical pros/cons applying. I have seen some cases where stub AS's >(those not providing transit) may have border routers communicating via BGP >to ISP's without peering amongst themselves but these are pretty unique >(weird) situations which often beg the question why BGP in the first place, >but this would be an fruitless digression. > >Pete > > >*** REPLY SEPARATOR *** > >On 8/8/2001 at 3:06 PM Ole Drews Jensen wrote: > >&g
RE: BGP: IBGP usage/clarification [7:15333]
Comments inline *** REPLY SEPARATOR *** On 8/8/2001 at 2:48 PM Ole Drews Jensen wrote: >Thanks Peter. > >I have browsed through Howards's BGP series, but for me, sometimes too long >explanations are more frustrating than a 10 words fact. > >Two additional questions if you don't mind, and you have a minute or two >:-) > >1) > >If you only have one BGP connection to one remote AS, IBGP would normally >never be used, and you would in most cases create a static default route to >the BGP router and redistribute it in your IGP. Am I right? > You are very correct and this is a typical use of default routing. IBGP by definition has no place here as it is a protocol used between BGP peers in the same AS and if you have only only router in the AS, nothing matches that criteria. >2) > >Should you have multiple BGP routers in the AS connected to two different >remote AS's - would I always configure IBGP between them, or would there be >situations where IBGP would still be unused? Keep in mind that IBGP distributes BGP learned routing information among peering routers within an AS. Hence, if you want border routers A and B to be aware of each others upstream connectivity, IBGP is your tool. Should you be providing transit, that is to say you are advertising that you can forward packets to destinations not originating in your AS, you will definitely require this functionality. Without it, A may advertise reachability to networks downstream of B that B, or other routers in the transit path from A to B do not know about. In this case you would blackhole those routes. In non transit AS's, your level of use of BGP can vary. If you have multiple providers and some redundancy in the way of multiple BGP speaking routers inside your AS, you could achieve gains in least cost forwarding by using IBGP to ensure all BGP speakers had the most accurate reachability information. It's really a balance here between how badly you need traffic to take the most optimal path out of your network and much you want to spend on infrastructure. Default routing is an excellent tool :) >Thanks again, > >Ole > >~~~ > Ole Drews Jensen > Systems Network Manager > CCNA, MCSE, MCP+I > RWR Enterprises, Inc. > [EMAIL PROTECTED] >~~~ > http://www.RouterChief.com >~~~ > NEED A JOB ??? > http://www.oledrews.com/job >~~~ > > >-Original Message- >From: Peter Van Oene [mailto:[EMAIL PROTECTED]] >Sent: Wednesday, August 08, 2001 2:38 PM >To: Ole Drews Jensen; [EMAIL PROTECTED] >Subject: Re: BGP: IBGP usage/clarification [7:15333] > > >A couple quick notes. However I would suggest if you have a subscription >that you step through Howards BGP series at www.certificationzone.com as it >might help you solidify your understanding. > >First off, IBGP is not an IGP. If you want to get from point A to point B >in AS C, IBGP isn't your friend (unless operator X tweaked IBGP with lots >of >messiness -ie NHS everywhere etc) IBGP facilitates inter-AS routing by >enabling reachability information to be maintained within AS's. IGP are >still required to enable routing within the AS (ie intra-AS routing). > >IBGP is used when you have multiple BGP routers in an AS. Really not much >more to it than that at a high level. Whether or not you chose to use a >dynamic IGP versus a static configuration really is up to the administrator >with typical pros/cons applying. I have seen some cases where stub AS's >(those not providing transit) may have border routers communicating via BGP >to ISP's without peering amongst themselves but these are pretty unique >(weird) situations which often beg the question why BGP in the first place, >but this would be an fruitless digression. > >Pete > > >*** REPLY SEPARATOR *** > >On 8/8/2001 at 3:06 PM Ole Drews Jensen wrote: > >>This might sound like a stupid question, but I have now read and >>practised a >>lot of BGP stuff, but there's one thing I am not 100% sure I understand; >>None of the books have been able to put the last brick in place in the >>puzzle for me. >> >>In what situations will "end-user" companies use IBGP and not just an IGP >>as >>OSPF or EIGRP? >> >>I believe that most ISP's use IBGP with a full mess where there are more >>than one EBGP connection - right? >> >>And a question to those of you who do a lot of BGP setup's for customers, >>how often do you typically use BGP at "end-user" companies and how often >>will IBGP be used ther
RE: BGP: IBGP usage/clarification [7:15333]
Thanks you Brian, I think I got it down now. I knew pretty much the karma of EBGP, but what confused me was that IBGP doesn't replace the necessity for an IGP. I kind of thought that IBGP could be used as an IGP, and suddently there were too many protocols running at the same time without making sense. Take care, Ole ~~~ Ole Drews Jensen Systems Network Manager CCNA, MCSE, MCP+I RWR Enterprises, Inc. [EMAIL PROTECTED] ~~~ http://www.RouterChief.com ~~~ NEED A JOB ??? http://www.oledrews.com/job ~~~ -Original Message- From: Brian [mailto:[EMAIL PROTECTED]] Sent: Wednesday, August 08, 2001 3:07 PM To: Ole Drews Jensen Cc: [EMAIL PROTECTED] Subject: RE: BGP: IBGP usage/clarification [7:15333] if you only had a connection to 1 as at one site, no reason to use bgp at all, just static default it. Redistributing bgp into an igp is generally not a good thing to do, it'll hammer an underequipped router.. Suppose u work for a company with connections to 2 isps. Further suppose that in order to not fall victim to hardware failure, you use different routers for each connection. How is 1 router supposed to know what routes the other peering session is receiveing?? IBGP is how that happens. You'd typically run IBGP between the 2 routers, so that you'd have the best of both available. Brian "Sonic" Whalen Success = Preparation + Opportunity On Wed, 8 Aug 2001, Ole Drews Jensen wrote: > Thanks Peter. > > I have browsed through Howards's BGP series, but for me, sometimes too long > explanations are more frustrating than a 10 words fact. > > Two additional questions if you don't mind, and you have a minute or two :-) > > 1) > > If you only have one BGP connection to one remote AS, IBGP would normally > never be used, and you would in most cases create a static default route to > the BGP router and redistribute it in your IGP. Am I right? > > 2) > > Should you have multiple BGP routers in the AS connected to two different > remote AS's - would I always configure IBGP between them, or would there be > situations where IBGP would still be unused? > > Thanks again, > > Ole > > ~~~ > Ole Drews Jensen > Systems Network Manager > CCNA, MCSE, MCP+I > RWR Enterprises, Inc. > [EMAIL PROTECTED] > ~~~ > http://www.RouterChief.com > ~~~ > NEED A JOB ??? > http://www.oledrews.com/job > ~~~ > > > -Original Message----- > From: Peter Van Oene [mailto:[EMAIL PROTECTED]] > Sent: Wednesday, August 08, 2001 2:38 PM > To: Ole Drews Jensen; [EMAIL PROTECTED] > Subject: Re: BGP: IBGP usage/clarification [7:15333] > > > A couple quick notes. However I would suggest if you have a subscription > that you step through Howards BGP series at www.certificationzone.com as it > might help you solidify your understanding. > > First off, IBGP is not an IGP. If you want to get from point A to point B > in AS C, IBGP isn't your friend (unless operator X tweaked IBGP with lots of > messiness -ie NHS everywhere etc) IBGP facilitates inter-AS routing by > enabling reachability information to be maintained within AS's. IGP are > still required to enable routing within the AS (ie intra-AS routing). > > IBGP is used when you have multiple BGP routers in an AS. Really not much > more to it than that at a high level. Whether or not you chose to use a > dynamic IGP versus a static configuration really is up to the administrator > with typical pros/cons applying. I have seen some cases where stub AS's > (those not providing transit) may have border routers communicating via BGP > to ISP's without peering amongst themselves but these are pretty unique > (weird) situations which often beg the question why BGP in the first place, > but this would be an fruitless digression. > > Pete > > > *** REPLY SEPARATOR *** > > On 8/8/2001 at 3:06 PM Ole Drews Jensen wrote: > > >This might sound like a stupid question, but I have now read and > >practised a > >lot of BGP stuff, but there's one thing I am not 100% sure I understand; > >None of the books have been able to put the last brick in place in the > >puzzle for me. > > > >In what situations will "end-user" companies use IBGP and not just an IGP > >as > >OSPF or EIGRP? > > > >I believe that most ISP's use IBGP with a full mess where there are more > >than one EBGP connection - right? > > > >And a question to those of you who do a
RE: BGP: IBGP usage/clarification [7:15333]
if you only had a connection to 1 as at one site, no reason to use bgp at all, just static default it. Redistributing bgp into an igp is generally not a good thing to do, it'll hammer an underequipped router.. Suppose u work for a company with connections to 2 isps. Further suppose that in order to not fall victim to hardware failure, you use different routers for each connection. How is 1 router supposed to know what routes the other peering session is receiveing?? IBGP is how that happens. You'd typically run IBGP between the 2 routers, so that you'd have the best of both available. Brian "Sonic" Whalen Success = Preparation + Opportunity On Wed, 8 Aug 2001, Ole Drews Jensen wrote: > Thanks Peter. > > I have browsed through Howards's BGP series, but for me, sometimes too long > explanations are more frustrating than a 10 words fact. > > Two additional questions if you don't mind, and you have a minute or two :-) > > 1) > > If you only have one BGP connection to one remote AS, IBGP would normally > never be used, and you would in most cases create a static default route to > the BGP router and redistribute it in your IGP. Am I right? > > 2) > > Should you have multiple BGP routers in the AS connected to two different > remote AS's - would I always configure IBGP between them, or would there be > situations where IBGP would still be unused? > > Thanks again, > > Ole > > ~~~ > Ole Drews Jensen > Systems Network Manager > CCNA, MCSE, MCP+I > RWR Enterprises, Inc. > [EMAIL PROTECTED] > ~~~ > http://www.RouterChief.com > ~~~ > NEED A JOB ??? > http://www.oledrews.com/job > ~~~ > > > -Original Message----- > From: Peter Van Oene [mailto:[EMAIL PROTECTED]] > Sent: Wednesday, August 08, 2001 2:38 PM > To: Ole Drews Jensen; [EMAIL PROTECTED] > Subject: Re: BGP: IBGP usage/clarification [7:15333] > > > A couple quick notes. However I would suggest if you have a subscription > that you step through Howards BGP series at www.certificationzone.com as it > might help you solidify your understanding. > > First off, IBGP is not an IGP. If you want to get from point A to point B > in AS C, IBGP isn't your friend (unless operator X tweaked IBGP with lots of > messiness -ie NHS everywhere etc) IBGP facilitates inter-AS routing by > enabling reachability information to be maintained within AS's. IGP are > still required to enable routing within the AS (ie intra-AS routing). > > IBGP is used when you have multiple BGP routers in an AS. Really not much > more to it than that at a high level. Whether or not you chose to use a > dynamic IGP versus a static configuration really is up to the administrator > with typical pros/cons applying. I have seen some cases where stub AS's > (those not providing transit) may have border routers communicating via BGP > to ISP's without peering amongst themselves but these are pretty unique > (weird) situations which often beg the question why BGP in the first place, > but this would be an fruitless digression. > > Pete > > > *** REPLY SEPARATOR *** > > On 8/8/2001 at 3:06 PM Ole Drews Jensen wrote: > > >This might sound like a stupid question, but I have now read and > >practised a > >lot of BGP stuff, but there's one thing I am not 100% sure I understand; > >None of the books have been able to put the last brick in place in the > >puzzle for me. > > > >In what situations will "end-user" companies use IBGP and not just an IGP > >as > >OSPF or EIGRP? > > > >I believe that most ISP's use IBGP with a full mess where there are more > >than one EBGP connection - right? > > > >And a question to those of you who do a lot of BGP setup's for customers, > >how often do you typically use BGP at "end-user" companies and how often > >will IBGP be used there with or without an IGR running on their network(s)? > > > >Thanks for any comments on this, > > > >Ole > > > >~~~ > > Ole Drews Jensen > > Systems Network Manager > > CCNA, MCSE, MCP+I > > RWR Enterprises, Inc. > > [EMAIL PROTECTED] > >~~~ > > http://www.RouterChief.com > >~~~ > > NEED A JOB ??? > > http://www.oledrews.com/job > >~~~ Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=15348&t=15333 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
RE: BGP: IBGP usage/clarification [7:15333]
Thanks Peter. I have browsed through Howards's BGP series, but for me, sometimes too long explanations are more frustrating than a 10 words fact. Two additional questions if you don't mind, and you have a minute or two :-) 1) If you only have one BGP connection to one remote AS, IBGP would normally never be used, and you would in most cases create a static default route to the BGP router and redistribute it in your IGP. Am I right? 2) Should you have multiple BGP routers in the AS connected to two different remote AS's - would I always configure IBGP between them, or would there be situations where IBGP would still be unused? Thanks again, Ole ~~~ Ole Drews Jensen Systems Network Manager CCNA, MCSE, MCP+I RWR Enterprises, Inc. [EMAIL PROTECTED] ~~~ http://www.RouterChief.com ~~~ NEED A JOB ??? http://www.oledrews.com/job ~~~ -Original Message- From: Peter Van Oene [mailto:[EMAIL PROTECTED]] Sent: Wednesday, August 08, 2001 2:38 PM To: Ole Drews Jensen; [EMAIL PROTECTED] Subject: Re: BGP: IBGP usage/clarification [7:15333] A couple quick notes. However I would suggest if you have a subscription that you step through Howards BGP series at www.certificationzone.com as it might help you solidify your understanding. First off, IBGP is not an IGP. If you want to get from point A to point B in AS C, IBGP isn't your friend (unless operator X tweaked IBGP with lots of messiness -ie NHS everywhere etc) IBGP facilitates inter-AS routing by enabling reachability information to be maintained within AS's. IGP are still required to enable routing within the AS (ie intra-AS routing). IBGP is used when you have multiple BGP routers in an AS. Really not much more to it than that at a high level. Whether or not you chose to use a dynamic IGP versus a static configuration really is up to the administrator with typical pros/cons applying. I have seen some cases where stub AS's (those not providing transit) may have border routers communicating via BGP to ISP's without peering amongst themselves but these are pretty unique (weird) situations which often beg the question why BGP in the first place, but this would be an fruitless digression. Pete *** REPLY SEPARATOR *** On 8/8/2001 at 3:06 PM Ole Drews Jensen wrote: >This might sound like a stupid question, but I have now read and >practised a >lot of BGP stuff, but there's one thing I am not 100% sure I understand; >None of the books have been able to put the last brick in place in the >puzzle for me. > >In what situations will "end-user" companies use IBGP and not just an IGP >as >OSPF or EIGRP? > >I believe that most ISP's use IBGP with a full mess where there are more >than one EBGP connection - right? > >And a question to those of you who do a lot of BGP setup's for customers, >how often do you typically use BGP at "end-user" companies and how often >will IBGP be used there with or without an IGR running on their network(s)? > >Thanks for any comments on this, > >Ole > >~~~ > Ole Drews Jensen > Systems Network Manager > CCNA, MCSE, MCP+I > RWR Enterprises, Inc. > [EMAIL PROTECTED] >~~~ > http://www.RouterChief.com >~~~ > NEED A JOB ??? > http://www.oledrews.com/job >~~~ Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=15345&t=15333 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: BGP: IBGP usage/clarification [7:15333]
A couple quick notes. However I would suggest if you have a subscription that you step through Howards BGP series at www.certificationzone.com as it might help you solidify your understanding. First off, IBGP is not an IGP. If you want to get from point A to point B in AS C, IBGP isn't your friend (unless operator X tweaked IBGP with lots of messiness -ie NHS everywhere etc) IBGP facilitates inter-AS routing by enabling reachability information to be maintained within AS's. IGP are still required to enable routing within the AS (ie intra-AS routing). IBGP is used when you have multiple BGP routers in an AS. Really not much more to it than that at a high level. Whether or not you chose to use a dynamic IGP versus a static configuration really is up to the administrator with typical pros/cons applying. I have seen some cases where stub AS's (those not providing transit) may have border routers communicating via BGP to ISP's without peering amongst themselves but these are pretty unique (weird) situations which often beg the question why BGP in the first place, but this would be an fruitless digression. Pete *** REPLY SEPARATOR *** On 8/8/2001 at 3:06 PM Ole Drews Jensen wrote: >This might sound like a stupid question, but I have now read and >practised a >lot of BGP stuff, but there's one thing I am not 100% sure I understand; >None of the books have been able to put the last brick in place in the >puzzle for me. > >In what situations will "end-user" companies use IBGP and not just an IGP >as >OSPF or EIGRP? > >I believe that most ISP's use IBGP with a full mess where there are more >than one EBGP connection - right? > >And a question to those of you who do a lot of BGP setup's for customers, >how often do you typically use BGP at "end-user" companies and how often >will IBGP be used there with or without an IGR running on their network(s)? > >Thanks for any comments on this, > >Ole > >~~~ > Ole Drews Jensen > Systems Network Manager > CCNA, MCSE, MCP+I > RWR Enterprises, Inc. > [EMAIL PROTECTED] >~~~ > http://www.RouterChief.com >~~~ > NEED A JOB ??? > http://www.oledrews.com/job >~~~ Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=15342&t=15333 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
