At each member AS, either IGRP or OSPF. They do not interact. By design... two of the AS's are across the Pacific from the other two :-) -Andy -- Andy McConnell アンディ マッコネル Network Architect, NTT Multimedia Communications Laboratories Slogan of 105.9, the classic rock radio station in Chicago: "Of all the radio stations in Chicago ... we're one of them." On Fri, 6 Mar 1998, Blake Willis wrote: blakew> Andy, blakew> blakew> What IGP are you running on this network? blakew> blakew> -Blake Willis blakew> CAIS Engineering blakew> blakew> --------------------------------------------------------------------------- blakew> Blake Willis 703-448-4470x483 blakew> Network Engineer, New Customers blakew@cais.net blakew> CAIS Internet, a CGX Communications Company blakew> --------------------------------------------------------------------------- blakew> blakew> On Fri, 6 Mar 1998, Andy McConnell wrote: blakew> blakew> > I have a problem I cannot solve. If anyone is running confederations like blakew> > mine, I would appreciate some help :-) blakew> > blakew> > We have a 4-memberAS confederation, each with two IBGP peers. The blakew> > arrangement looks sort of like an octagon. the "r" is AS3 is an internal blakew> > hop, not a BGP peer. blakew> > blakew> > _______ ______ blakew> > | R-----R---r | blakew> > | / | | | | blakew> > |AS2 R | |AS3 R | blakew> > ----|-- ----|- blakew> > | | blakew> > ____|__ ____|_ blakew> > |AS4 R | |AS1 R | blakew> > | \ | | / | blakew> > | R-------R | blakew> > ------- ------ blakew> > blakew> > The problem is this: How do you get BGP to choose the shortest "AS PATH", blakew> > since internal AS paths are ignored in selecting BGP routes? Right now, blakew> > to top router in AS4 will always choose a route through (2 3 1) instead of blakew> > (1), because it prefers "external" routes (even external confederation blakew> > routes) over internal routes. blakew> > blakew> > So, when given a choice, the router on the distant side of the AS will blakew> > ALWAYS prefer the three-AS-hop path, because it is external. Is there a blakew> > way around this?!? blakew> > blakew> > Avi Freedman suggested using a +1 metric when leaving each member-AS. blakew> > (Thanks Avi!) But it doesn't seem to help - perhaps I didn't do it right. blakew> > In fact, it doesn't look like the metrics are adjusted more than 1. for blakew> > example, from AS2, the lower router sees every route outside of AS2 as blakew> > having only metric 1! The top router in AS3 does not add 1 to the metrics blakew> > it readvertises to AS2. blakew> > blakew> > I've been stewing over this problem for some time... I believe there is blakew> > some clue that I've missed. Any help would be greatly appreciated! blakew> > blakew> > -Andy blakew> > blakew> > blakew> > -- blakew> > Andy McConnell アンディ マッコネル blakew> > Network Architect, NTT Multimedia Communications Laboratories blakew> > blakew> > Writing about music is like dancing about architecture. blakew> > blakew>
Andy, I would say that you should switch to two confeds, one on either side of the ocean. That should take care of the problem. BTW, did Minyah ever get her NAT problem straightened out? -Blake --------------------------------------------------------------------------- Blake Willis 703-448-4470x483 Network Engineer, New Customers blakew@cais.net CAIS Internet, a CGX Communications Company --------------------------------------------------------------------------- On Fri, 6 Mar 1998, Andy McConnell wrote:
At each member AS, either IGRP or OSPF. They do not interact. By design... two of the AS's are across the Pacific from the other two :-)
-Andy
-- Andy McConnell $B%"%s%G%#(B $B%^%C%3%M%k(B Network Architect, NTT Multimedia Communications Laboratories
Slogan of 105.9, the classic rock radio station in Chicago: "Of all the radio stations in Chicago ... we're one of them."
On Fri, 6 Mar 1998, Blake Willis wrote:
blakew> Andy, blakew> blakew> What IGP are you running on this network? blakew> blakew> -Blake Willis blakew> CAIS Engineering blakew> blakew> --------------------------------------------------------------------------- blakew> Blake Willis 703-448-4470x483 blakew> Network Engineer, New Customers blakew@cais.net blakew> CAIS Internet, a CGX Communications Company blakew> --------------------------------------------------------------------------- blakew> blakew> On Fri, 6 Mar 1998, Andy McConnell wrote: blakew> blakew> > I have a problem I cannot solve. If anyone is running confederations like blakew> > mine, I would appreciate some help :-) blakew> > blakew> > We have a 4-memberAS confederation, each with two IBGP peers. The blakew> > arrangement looks sort of like an octagon. the "r" is AS3 is an internal blakew> > hop, not a BGP peer. blakew> > blakew> > _______ ______ blakew> > | R-----R---r | blakew> > | / | | | | blakew> > |AS2 R | |AS3 R | blakew> > ----|-- ----|- blakew> > | | blakew> > ____|__ ____|_ blakew> > |AS4 R | |AS1 R | blakew> > | \ | | / | blakew> > | R-------R | blakew> > ------- ------ blakew> > blakew> > The problem is this: How do you get BGP to choose the shortest "AS PATH", blakew> > since internal AS paths are ignored in selecting BGP routes? Right now, blakew> > to top router in AS4 will always choose a route through (2 3 1) instead of blakew> > (1), because it prefers "external" routes (even external confederation blakew> > routes) over internal routes. blakew> > blakew> > So, when given a choice, the router on the distant side of the AS will blakew> > ALWAYS prefer the three-AS-hop path, because it is external. Is there a blakew> > way around this?!? blakew> > blakew> > Avi Freedman suggested using a +1 metric when leaving each member-AS. blakew> > (Thanks Avi!) But it doesn't seem to help - perhaps I didn't do it right. blakew> > In fact, it doesn't look like the metrics are adjusted more than 1. for blakew> > example, from AS2, the lower router sees every route outside of AS2 as blakew> > having only metric 1! The top router in AS3 does not add 1 to the metrics blakew> > it readvertises to AS2. blakew> > blakew> > I've been stewing over this problem for some time... I believe there is blakew> > some clue that I've missed. Any help would be greatly appreciated! blakew> > blakew> > -Andy blakew> > blakew> > blakew> > -- blakew> > Andy McConnell $B%"%s%G%#(B $B%^%C%3%M%k(B blakew> > Network Architect, NTT Multimedia Communications Laboratories blakew> > blakew> > Writing about music is like dancing about architecture. blakew> > blakew>
Hey Andy if it is a Confederation the BGP is treated like IBGP even if it is EBGP so you can set a MED value to favor a specific route, you can also manipulate the AS_PATH attribute - appending the AS number 2 or more times to the announcement for the least favored route applied to the appropriate interface. Since it's all considerred IBGP simply set the MED to 50 on the least favored and 20 on the favored - or what ever incriments you deem appropriate. You may have to set "bgp always-compare-med" for it to be considered on multiple AS numbers within a confederation though. On Fri, 6 Mar 1998, Andy McConnell wrote:
At each member AS, either IGRP or OSPF. They do not interact. By design... two of the AS's are across the Pacific from the other two :-)
-Andy
-- Andy McConnell $B%"%s%G%#(B $B%^%C%3%M%k(B Network Architect, NTT Multimedia Communications Laboratories
Slogan of 105.9, the classic rock radio station in Chicago: "Of all the radio stations in Chicago ... we're one of them."
On Fri, 6 Mar 1998, Blake Willis wrote:
blakew> Andy, blakew> blakew> What IGP are you running on this network? blakew> blakew> -Blake Willis blakew> CAIS Engineering blakew> blakew> --------------------------------------------------------------------------- blakew> Blake Willis 703-448-4470x483 blakew> Network Engineer, New Customers blakew@cais.net blakew> CAIS Internet, a CGX Communications Company blakew> --------------------------------------------------------------------------- blakew> blakew> On Fri, 6 Mar 1998, Andy McConnell wrote: blakew> blakew> > I have a problem I cannot solve. If anyone is running confederations like blakew> > mine, I would appreciate some help :-) blakew> > blakew> > We have a 4-memberAS confederation, each with two IBGP peers. The blakew> > arrangement looks sort of like an octagon. the "r" is AS3 is an internal blakew> > hop, not a BGP peer. blakew> > blakew> > _______ ______ blakew> > | R-----R---r | blakew> > | / | | | | blakew> > |AS2 R | |AS3 R | blakew> > ----|-- ----|- blakew> > | | blakew> > ____|__ ____|_ blakew> > |AS4 R | |AS1 R | blakew> > | \ | | / | blakew> > | R-------R | blakew> > ------- ------ blakew> > blakew> > The problem is this: How do you get BGP to choose the shortest "AS PATH", blakew> > since internal AS paths are ignored in selecting BGP routes? Right now, blakew> > to top router in AS4 will always choose a route through (2 3 1) instead of blakew> > (1), because it prefers "external" routes (even external confederation blakew> > routes) over internal routes. blakew> > blakew> > So, when given a choice, the router on the distant side of the AS will blakew> > ALWAYS prefer the three-AS-hop path, because it is external. Is there a blakew> > way around this?!? blakew> > blakew> > Avi Freedman suggested using a +1 metric when leaving each member-AS. blakew> > (Thanks Avi!) But it doesn't seem to help - perhaps I didn't do it right. blakew> > In fact, it doesn't look like the metrics are adjusted more than 1. for blakew> > example, from AS2, the lower router sees every route outside of AS2 as blakew> > having only metric 1! The top router in AS3 does not add 1 to the metrics blakew> > it readvertises to AS2. blakew> > blakew> > I've been stewing over this problem for some time... I believe there is blakew> > some clue that I've missed. Any help would be greatly appreciated! blakew> > blakew> > -Andy blakew> > blakew> > blakew> > -- blakew> > Andy McConnell $B%"%s%G%#(B $B%^%C%3%M%k(B blakew> > Network Architect, NTT Multimedia Communications Laboratories blakew> > blakew> > Writing about music is like dancing about architecture. blakew> > blakew>
-- I am nothing if not net-Q! - ras@poppa.clubrich.tiac.net
But it isn't considered IBGP within the confederation. The router makes a distinction between routes learned from an IBGP peer (internal) and a confederation EBGP peer (confederation-external) and will ALWAYS pick the external route, all other items above it in the selection list being equal. I've eliminated trying to increase the AS path, since it's ignored within the confederation. Setting the MED is the crux of the problem - I can set it "statically", but the idea is to make the whole confederation dynamic. I want the confederation to work like a true "internet". (Yes, I'm asking for the world...) -Andy -- Andy McConnell アンディ マッコネル Network Architect, NTT Multimedia Communications Laboratories I think myself that we have more machinery of government than is necessary, too many parasites living on the labor of the industrious. -- Thomas Jefferson, 1812 On Sat, 7 Mar 1998, Rich Sena wrote: ras> ras> Hey Andy if it is a Confederation the BGP is treated like IBGP even if it ras> is EBGP so you can set a MED value to favor a specific route, you can also ras> manipulate the AS_PATH attribute - appending the AS number 2 or more times ras> to the announcement for the least favored route applied to the appropriate ras> interface. ras> ras> Since it's all considerred IBGP simply set the MED to 50 on the least ras> favored and 20 on the favored - or what ever incriments you deem ras> appropriate. ras> ras> You may have to set "bgp always-compare-med" for it to be considered on ras> multiple AS numbers within a confederation though. ras> ras> On Fri, 6 Mar 1998, Andy McConnell wrote: ras> ras> > At each member AS, either IGRP or OSPF. They do not interact. By ras> > design... two of the AS's are across the Pacific from the other two :-) ras> > ras> > -Andy ras> > ras> > -- ras> > Andy McConnell アンディ マッコネル ras> > Network Architect, NTT Multimedia Communications Laboratories ras> > ras> > Slogan of 105.9, the classic rock radio station in Chicago: "Of ras> > all the radio stations in Chicago ... we're one of them." ras> > ras> > On Fri, 6 Mar 1998, Blake Willis wrote: ras> > ras> > blakew> Andy, ras> > blakew> ras> > blakew> What IGP are you running on this network? ras> > blakew> ras> > blakew> -Blake Willis ras> > blakew> CAIS Engineering ras> > blakew> ras> > blakew> --------------------------------------------------------------------------- ras> > blakew> Blake Willis 703-448-4470x483 ras> > blakew> Network Engineer, New Customers blakew@cais.net ras> > blakew> CAIS Internet, a CGX Communications Company ras> > blakew> --------------------------------------------------------------------------- ras> > blakew> ras> > blakew> On Fri, 6 Mar 1998, Andy McConnell wrote: ras> > blakew> ras> > blakew> > I have a problem I cannot solve. If anyone is running confederations like ras> > blakew> > mine, I would appreciate some help :-) ras> > blakew> > ras> > blakew> > We have a 4-memberAS confederation, each with two IBGP peers. The ras> > blakew> > arrangement looks sort of like an octagon. the "r" is AS3 is an internal ras> > blakew> > hop, not a BGP peer. ras> > blakew> > ras> > blakew> > _______ ______ ras> > blakew> > | R-----R---r | ras> > blakew> > | / | | | | ras> > blakew> > |AS2 R | |AS3 R | ras> > blakew> > ----|-- ----|- ras> > blakew> > | | ras> > blakew> > ____|__ ____|_ ras> > blakew> > |AS4 R | |AS1 R | ras> > blakew> > | \ | | / | ras> > blakew> > | R-------R | ras> > blakew> > ------- ------ ras> > blakew> > ras> > blakew> > The problem is this: How do you get BGP to choose the shortest "AS PATH", ras> > blakew> > since internal AS paths are ignored in selecting BGP routes? Right now, ras> > blakew> > to top router in AS4 will always choose a route through (2 3 1) instead of ras> > blakew> > (1), because it prefers "external" routes (even external confederation ras> > blakew> > routes) over internal routes. ras> > blakew> > ras> > blakew> > So, when given a choice, the router on the distant side of the AS will ras> > blakew> > ALWAYS prefer the three-AS-hop path, because it is external. Is there a ras> > blakew> > way around this?!? ras> > blakew> > ras> > blakew> > Avi Freedman suggested using a +1 metric when leaving each member-AS. ras> > blakew> > (Thanks Avi!) But it doesn't seem to help - perhaps I didn't do it right. ras> > blakew> > In fact, it doesn't look like the metrics are adjusted more than 1. for ras> > blakew> > example, from AS2, the lower router sees every route outside of AS2 as ras> > blakew> > having only metric 1! The top router in AS3 does not add 1 to the metrics ras> > blakew> > it readvertises to AS2. ras> > blakew> > ras> > blakew> > I've been stewing over this problem for some time... I believe there is ras> > blakew> > some clue that I've missed. Any help would be greatly appreciated! ras> > blakew> > ras> > blakew> > -Andy ras> > blakew> > ras> > blakew> > ras> > blakew> > -- ras> > blakew> > Andy McConnell アンディ マッコネル ras> > blakew> > Network Architect, NTT Multimedia Communications Laboratories ras> > blakew> > ras> > blakew> > Writing about music is like dancing about architecture. ras> > blakew> > ras> > blakew> ras> > ras> ras> -- ras> I am nothing if not net-Q! - ras@poppa.clubrich.tiac.net ras>
: Andy McConnell <andym@nttlabs.com> wrote as below : at Mon, 9 Mar 1998 08:57:29 -0800 (PST) ; : :| But it isn't considered IBGP within the confederation. The router makes a :| distinction between routes learned from an IBGP peer (internal) and a :| confederation EBGP peer (confederation-external) and will ALWAYS pick the :| external route, all other items above it in the selection list being :| equal. :| :| I've eliminated trying to increase the AS path, since it's ignored within :| the confederation. :| :| Setting the MED is the crux of the problem - I can set it "statically", :| but the idea is to make the whole confederation dynamic. I want the :| confederation to work like a true "internet". (Yes, I'm asking for the :| world...) :| Andy, I agree with you. I run bgp-confederation in my network with IGP in each subAS independant. In this case it is helpful if ASpath length within confederation is considered as true eBGP. Now I set MED statically. Thank you for information of "set metric +/-[VALUE]" statement, I'll try it. Nowaday, iBGP Reflecter is preferred to BGP Confederation. When we use single IGP within AS, reflecter and confederation make little difference. But confederation enable us to divide IGP into sub-ASes. It may make sense a lot. And in such a network configuration, it is natural that AS path length consideration while route selection is required. How do you like this idea?? Is it IDR topic?? :| -Andy :| ----- MAEMURA Akinori Network Engineer, C&C Internet Service mesh, NEC Corporation, JAPAN maem@mesh.ad.jp, maemura@mms.mt.nec.co.jp
I agree with you, Andy. I run bgp-confederation in my network with IGP divided into subASes. Your situation is a little bit different from mine without any iBGP sessions now. But the problem is similar, AS path length is never considered in route selection. I set MED statically. Thank you Avi and Andy for the information of "set metric +/-[VALUE]" statement. I'll try it. Route reflecter and confederation seem similar to each other to solve iBGP mesh problem, and nowaday reflecter is preferred to confed. But I think confederation is great since it enables us to divide IGP into subASes. And in such a network configuration, it is natural that AS path length is considered for the route selection. How do you like this idea, folks? : Andy McConnell <andym@nttlabs.com> wrote as below : at Mon, 9 Mar 1998 08:57:29 -0800 (PST) ; : :| But it isn't considered IBGP within the confederation. The router makes a :| distinction between routes learned from an IBGP peer (internal) and a :| confederation EBGP peer (confederation-external) and will ALWAYS pick the :| external route, all other items above it in the selection list being :| equal. :| :| I've eliminated trying to increase the AS path, since it's ignored within :| the confederation. :| :| Setting the MED is the crux of the problem - I can set it "statically", :| but the idea is to make the whole confederation dynamic. I want the :| confederation to work like a true "internet". (Yes, I'm asking for the :| world...) :| :| -Andy :| ----- MAEMURA Akinori Network Engineer, C&C Internet Service mesh, NEC Corporation, JAPAN maem@mesh.ad.jp, maemura@mms.mt.nec.co.jp
But it isn't considered IBGP within the confederation. The router makes a distinction between routes learned from an IBGP peer (internal) and a confederation EBGP peer (confederation-external) and will ALWAYS pick the external route, all other items above it in the selection list being equal.
I think you want the cisco "distance bgp" command. --apb (Alan Barrett)
participants (5)
-
Alan Barrett -
Andy McConnell -
Blake Willis -
MAEMURA Akinori -
Rich Sena