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Thread Index Re:[isp-bgp] And how i use load sharing in inbound traffic?
Previous | Next | Back to Messages Printable View - Full Headers Delete Reply Forward Spam Move... This message is not flagged. [ Flag Message - Mark as Unread ] Date: Sat, 11 Dec 2004 00:15:18 -0800 Subject: isp-bgp digest: December 10, 2004 To: "isp-bgp digest recipients" <isp-bgp@...> From: "ISP-BGP Discussion List digest" <isp-bgp@...> Add to Address BookAdd to Address Book ISP-BGP Digest for Friday, December 10, 2004. 1. Re: How to properly utilize backup link in multi-homed setup? 2. Re: How to properly utilize backup link in multi-homed setup? 3. Re: How to properly utilize backup link in multi-homed setup? 4. Example 5. Re: isp-bgp digest: December 07, 2004 6. Re:How to properly utilize backup link in multi-homed setup? 7. Re:How to properly utilize backup link in multi-homed setup? 8. Re: How to properly utilize backup link in multi-homed setup? 9. Re: How to properly utilize backup link in multi-homed setup? 10. Re: Example 11. Re: How to properly utilize backup link in multi-homed setup? 12. Re: How to properly utilize backup link in multi-homed setup? ---------------------------------------------------------------------- Subject: Re: How to properly utilize backup link in multi-homed setup? From: Pete Templin <petelists@...> Date: Fri, 10 Dec 2004 05:51:33 -0600 X-Message-Number: 1 Colo Host wrote: > Hello all, I'm hoping someone could give me a suggestion on how > to only make use of a backup link when the primary is down. The > setup is two border routers, router #1 and router #2. #1 has > connectivity to Level 3 (ASN 3356) and Global Crossing (ASN 3549). > We've just added router #2 and it has a link to Level 3 (ASN 3356) > which is to only be used if the primary link to them were to fail and > will soon have a third provider brought on. > > I don't think setting local preference lower on the backup link will > work because I believe local preference is not AS-specific and > would cause all outbound traffic to prefer Global Crossing on router > #1 if the primary Level 3 link were to fail since it would have a > higher local preference than the backup Level 3 link. I'm thinking > I could get Level 3 to send me MEDs to prefer the primary link > but is there any other way I can force it myself on my side? MED is your friend. Unlike weight and local pref, low MED wins. Set a low MED (say 50) on all announcements to L3 over the primary link and on all routes learned from L3 over the primary link, and a high MED (say 1,000,000) on all announcements to L3 over the backup link and on all routes learned from L3 learned from L3 over the backup link. If they do any MED twiddling in their network, the large difference in values should suffice. You may see trace amounts of traffic over the backup link, for BGP updates and any traffic due to slightly unsynchronized BGP tables, etc. Remember that outbound MED must be set on the EBGP egress point, or it'll get reset to 0 at the EBGP egress point. Inbound MED can be set anywhere, but remember that it'll get flushed if/when it leaves your network again. Ought to work like a charm... pt ---------------------------------------------------------------------- Subject: Re: How to properly utilize backup link in multi-homed setup? From: Pete Templin <petelists@...> Date: Fri, 10 Dec 2004 05:54:13 -0600 X-Message-Number: 2 Colo Host wrote: > Hello all, I'm hoping someone could give me a suggestion on how > to only make use of a backup link when the primary is down. The > setup is two border routers, router #1 and router #2. #1 has > connectivity to Level 3 (ASN 3356) and Global Crossing (ASN 3549). > We've just added router #2 and it has a link to Level 3 (ASN 3356) > which is to only be used if the primary link to them were to fail and > will soon have a third provider brought on. > > I don't think setting local preference lower on the backup link will > work because I believe local preference is not AS-specific and > would cause all outbound traffic to prefer Global Crossing on router > #1 if the primary Level 3 link were to fail since it would have a > higher local preference than the backup Level 3 link. I'm thinking > I could get Level 3 to send me MEDs to prefer the primary link > but is there any other way I can force it myself on my side? MED is your friend. Unlike weight and local pref, low MED wins. Set a low MED (say 50) on all announcements to L3 over the primary link and on all routes learned from L3 over the primary link, and a high MED (say 1,000,000) on all announcements to L3 over the backup link and on all routes learned from L3 learned from L3 over the backup link. If they do any MED twiddling in their network, the large difference in values should suffice. You may see trace amounts of traffic over the backup link, for BGP updates and any traffic due to slightly unsynchronized BGP tables, etc. Remember that outbound MED must be set on the EBGP egress point, or it'll get reset to 0 at the EBGP egress point. Inbound MED can be set anywhere, but remember that it'll get flushed if/when it leaves your network again. Ought to work like a charm... pt ---------------------------------------------------------------------- Subject: Re: How to properly utilize backup link in multi-homed setup? From: "Ejay Hire" <ejayhire@...> Date: Fri, 10 Dec 2004 11:57:57 -0600 X-Message-Number: 3 Hello. Primary and backup with bgp is easy. For inbound traffic, there are two ways to do it. 1. The easy way, if you have a /23 or larger is to send your specific advertisements to your primary provider, and an aggregate to the backup. i.e. announce 2 /24's to your primary(ies) and the same netblock as a /23 to the backup provider. 2. The not-so-easy way, announce the routes to all providers, and set a community on the route announced to the backup provider that causes them to set a localpref lower than that of the routes they learn through their other peers. i.e. you send a route to mci with the 701:90 community. They set a localpref of 90 on that route inside their network. they learn about the same network through their peer connections, with a default localpref of 100. they will use the peer route instead of your connected route. Outbound control is a LOT simpler. Accept a default route from both providers. use a route-map to set a localpref of 90 on the backup provider's default route. -Ejay Hire --- old message --- From: "Colo Host" <ispcolohost@...> Date: Sun, 05 Dec 2004 13:09:38 -0500 X-Message-Number: 1 Hello all, I'm hoping someone could give me a suggestion on how to only make use of a backup link when the primary is down. The setup is two border routers, router #1 and router #2. #1 has connectivity to Level 3 (ASN 3356) and Global Crossing (ASN 3549). We've just added router #2 and it has a link to Level 3 (ASN 3356) which is to only be used if the primary link to them were to fail and will soon have a third provider brought on. --- snip --- _________________________________________________________________ Don’t just search. Find. Check out the new MSN Search! http://search.msn.click-url.com/go/onm00200636ave/direct/01/ ---------------------------------------------------------------------- Subject: Example From: Marcelo Moulin <reckor@....br> Date: Fri, 10 Dec 2004 16:14:46 -0300 X-Message-Number: 4 Hi Sawarkar, And how i use load sharing in inbound traffic? Regards, Marcelo Moulin ------------------------------------------------------- Hello Marcelo Not possible unless you can manipulate attributes all the way upto the NAP. If I find a possible solution using "communities" I'll let you know later ... :) Best Regards Rahul S __________________________________ Do you Yahoo!? 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